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Part O of the Building Regulations in England sets out requirements for overheating. It was a new part of the Building Regulations in 2021 and will be intrinsic to the overarching Future Homes Standard due to be introduced this year. Wales and Scotland have their own overheating requirements, albeit the overall aims across the different countries are similar. Limiting the potential for dwellings to overheat is particularly critical as the climate continues to warm. Overheating is not just a comfort issue; it is a health issue and must be addressed as the likelihood of summer heatwaves continues to increase. Rooflights have a role to play in overheating control, especially as the use of mechanical cooling is restricted. What are the requirements of Part O 2021? There is a single requirement to Part O, which states unwanted solar gains should be limited in summer and there should be an adequate means to remove heat from the dwelling. There are two ways to assess overheating risk in dwellings: a simplified approach and dynamic thermal modelling. The simplified approach is generally sufficient for individual homes. It sets maximum limits on glazing areas to prevent excessive solar gains. It also sets minimum limits on ventilation free areas, with the aim of ensuring excess heat is removed via ventilation. Dynamic thermal modelling is carried out in accordance with CIBSE TM59 and is more accurate than the simplified approach. It sets comfort criteria by accounting for various parameters that affect internal temperatures, such as weather data, thermal mass, orientation of the dwelling, occupancy and internal heat gains. Approved Document O makes clear that its purpose is to protect the health and welfare of people within the dwelling. It does not guarantee their comfort. How can rooflights help to achieve Part O compliance? Record-breaking heatwaves in recent years have focused attention on overheating, giving it the same kind of prominence as the effect of cold weather on people’s health. The need to consider our changing climate is leading some planning authorities to ask for overheating to be assessed not just on current weather data, but also weather projections for 2050 and 2080. Dwellings must be able to demonstrate passive cooling strategies that meet the comfort criteria for these predicted future conditions. That is likely to mean increased specification of solar control features on glazing, combined with external shading devices. However, it also expands the role that rooflights can play in helping to achieve comfortable dwellings for the future. Orientation of the building is obviously critical to the likelihood of overheating. East-facing elevations get the morning sun, while south- and west-facing elevations are exposed to the hottest times of day. North-facing elevations, meanwhile, receive no direct sunlight. There is likely to be greater scope for individual dwellings to be designed to maximise the benefits of different orientations, and minimise the drawbacks. That depends on having a relatively unrestricted plot, and little other surrounding development to dictate where and how the dwelling must be positioned. Apartments are often very restricted, sometimes having only a single aspect. Depending on the design of the building overall, larger and more luxurious apartments located at the top of the building might offer multiple aspects. However, the need to accommodate more than one apartment at that level puts limitations on maximising orientation, with each apartment requiring a unique solution based on its different aspects. For both individual dwellings and apartments, specifying rooflights as well as façade glazing increases the options available for controlling solar gains and reducing overheating risk, while still providing high levels of daylight. Since warm air rises, opening rooflights are the most effective way of losing excess heat in conjunction with opening windows to allow fresh replacement air into the building. Positioning rooflights on the opposite side of windows in a dwelling or apartment can help to achieve effective cross ventilation. As well as contributing to fresh air provision, cross ventilation is a passive cooling technique that has long been a feature in hot and humid climates. As we come to terms with living in a warming climate, cross ventilation will be an increasingly important tool for maintaining the health and wellbeing of building occupants. Using rooflights to go beyond the minimum standard of Part O Like all areas of building regulations, Part O only sets out a minimum standard. The option to go beyond the requirements is always available and can be easily justified in this case – we have already seen that Part O doesn’t seek to achieve comfort for the occupants of a dwelling. A frequent criticism of regulations is that requirements in one area don’t necessarily complement the requirements in another area. The typical example is how energy performance requirements have improved, without ventilation requirements improving to the same level. Changes to the regulations are only just beginning to overcome this disconnect, hence the introduction of Part O. Designers and specifiers of prestigious homes and high-end apartments don’t have to wait for the regulations to be completely holistic. They can deliver a joined-up approach now to benefit their clients and add value to their projects. The blank canvas of a new project offers the opportunity to go beyond minimum standards. Project teams now routinely look to the forthcoming Future Homes Standard, and factor in predicted future climate conditions, to benchmark performance now. Rooflights can provide homes with a level and quality of daylight that vertical windows alone struggle to achieve. Perhaps more importantly, they have a significant role to play in helping to mitigate overheating risk, at a time when the regulatory requirement for such mitigation is not fully mature.

Structural floor loadings for walk on glass rooflights should be stated as Uniform Distributed Load (UDL) and Concentrated Load. Although you should expect a manufacturer or supplier to confirm what loadings the glass is designed to withstand, you should not expect them to provide information on the loadings themselves; this remains the responsibility of the specifier. For example, if you are working on a scheme that involves a glazed floor section in a commercial shopping centre, you must provide the loadings that are relevant to this specific application in accordance with British Standards. The supplier will then ensure that the glass provided will meet those demands. In order to establish what these loadings might be you should refer to BS EN 1991-1-1:2002, Eurocode 1: Actions on structures which covers General actions, densities, self-weight, and imposed loads for buildings. Further information regarding UK specific loadings can be found in the UK National Annex to Eurocode 1 (NA to BS EN 1991-1-1-1:2002). The loadings for any glass rooflight designed for deliberate foot traffic will depend on building type and specific use, but typically you might expect to see load capacities of the following magnitude: Domestic applications Uniformly distributed load (UDL) from 1.5kN/m2 Concentrated load from 2.0kN Commercial applications Uniformly distributed load (UDL) 4.0kN/m2 Concentrated load 3.6kN Heavy duty commercial applications Uniformly distributed load (UDL) 5.0kN/m2 Concentrated load 4.5kN Glass specifications for walk on rooflights For walk on specification rooflights the outer pane of glass should always be both toughened and laminated. It should be specifically designed for the pane size and method of support. The outer pane will vary dependant on intended use and will usually comprise of two or more leaves laminated together; occasionally an additional sacrificial layer of annealed glass is used on the surface. The increased thickness of this type of glass results in a heavier product when compared with non-walk on rooflights and consideration should be given to the supporting roof structure and site logistics. Weights may typically range from 95 kg/m2 – 110 kg/m2. You might also be interested to read our post on the difference between non fragile and walk on glass and anti-slip walk on glass. To find our more about specifying rooflights book a CPD which would be delivered by a member of our expert technical team.

The benefits of specifying rooflights and roof windows are clear: they provide high levels of natural light, they can be wonderful sources of ventilation, and they contribute to the thermal comfort of a building. Roof windows and rooflights also provide an aesthetically pleasing addition to the external appearance of a property. But what else should you consider to ensure the specification runs smoothly once it gets to site? Roof windows and rooflights are generally easy to install, but knowing what to expect can help to ensure things go smoothly. We have exclusive insights from Clarkson Builders about how to ensure proper specification and keep work on-site progressing as expected. Here are the things they recommend specifiers should be aware of: Window size Roof windows and rooflights come in an array of shapes and sizes, and choosing the right dimensions for your project is critical. The ‘standard’ for roof windows is 900x600mm, and these are installed between rafters at 600mm centres. Other common sizes are 980x980mm and 900x1200mm – the latter is designed to fit in a double-rafter space. They can also be provided in much larger sizes – for example, the Glazing Vision Pitchglaze Roof Window stocked on rooflights.com can measure up to 3000x1000mm. Structural support The most effective way of supporting a roof window is to use double trimmers for horizontal support and double rafters for vertical support. Double hangers are placed in each corner, and single hangers are located around connected rafters. The double supports comprise two pieces of rafter timber with 600mm centres (either C16 or C24 between 100x50mm or 225x50mm, depending on specification and structural calculations). The rafters should be fixed together with bulldog timber connectors and M12 bolts. When fixing the timber, the head of the bolt should be recessed on the side of the wood to which the rooflight will be fixed. Otherwise, it could protrude into the area beneath the glazing. As with all structural requirements, relevant calculations should be carried out by a qualified structural engineer. Preparing the window aperture Remember that the size of the window aperture may not be the size of the window itself. The actual requirements will depend on the individual roof window, so be sure to consult your desired manufacturer early in the planning stages. When preparing the rafters, consider how elements like the insulation sarking and the ends of the battens will be supported. The roofing underlay should be folded back and fixed appropriately. Other elements will also need to be added to the roof, such as tilting fillets, battens and flashing. Out-of-plane rooflights will also require the construction of an upstand. Site delivery and storage Take time to consider how rooflights and roof windows will get to site – and once there, how will the units be stored to ensure they aren’t damaged. In addition, don’t underestimate the weight of a roof window. A small, 750x750mm laminated rooflight weighs just over 31kg, and the units can reach more than 150kg, depending on the size and type of glazing. Heavier units should also be assessed in terms of Health and Safety. Mechanical assistance should be utilised for moving the roof windows around the site safely. Getting the roof window or rooflight onto the roof In most cases, construction materials are delivered ‘to the kerb’, and this is the case for rooflights and roof windows. Unless you have a particularly obliging driver, you will need to work out how to get the unit onto the roof. As discussed in the previous section, roof windows can be very heavy and lifting them in a way that avoids damage or injury will require careful planning. It could also incur extra costs – you may need to hire lifting equipment for bulky units, or for hard-to-access locations. Instructions and tools Many roof windows come with an installation guide that actually covers multiple products – and those products can look very similar while having slightly different fixings and flashings. If these instructions aren’t followed correctly, it could impact the installation process and how the roof window or rooflight performs. Be sure to check the instructions to ensure that the installation team has the right tools. Depending on the manufacturer, special drill bits may be required. For example, Velux windows use a screw that uses a T20 drill bit that’s commonly used for day-to-day work on building sites. Tiling around roof windows Roof windows are usually found on pitched roofs (unlike roof lights, typically found on flat roofs). When tiling around roof windows, it’s important to ensure that the bottom tile is not too close to the window, as the flashing cannot be installed correctly. The best way to plan the tile gauge is to measure from the bottom of the roof, as this allows for the best finish and helps to ensure the roof window performance isn’t compromised. When using pantiles (these are usually made from concrete but may also be clay in heritage projects), be sure to chamfer the top of the bold roll beneath the window. This should all be explained in the instruction manual, which should outline the distances to install your battens to the sides, top and bottom of the window. With so much to think about, it’s easy to see why it’s so important to look beyond appearance and performance of a building element at the specification stage. If you have any questions or concerns about a product you’re specifying, it’s a good idea to get answers and advice as soon as possible from the manufacturer.

Part L of the Building Regulations in England sets out requirements for the conservation of fuel and power, or energy efficiency as it might be more commonly termed. The current version is Part L 2021, which is expected to be replaced by a new version later this year as part of the overarching Future Homes Standard. Wales and Scotland have their own energy efficiency requirements. High standards of building fabric performance, supported by low U-values and a good standard of airtightness, are essential for meeting current or future regulations in all parts of the UK. Rooflights are part of the building fabric, and so must play their part in delivering energy efficiency as part of overall building performance. What are the requirements of Part L 2021? As Approved Document L volume 1 says, “A new dwelling must be built to a minimum standard of energy performance.” To assess that performance, the dwelling’s specification is compared to that of a theoretical dwelling, called the notional dwelling. The calculation method for making the assessment is the Standard Assessment Procedure, or SAP. The actual dwelling must meet or exceed the targets set by the notional dwelling in the following areas. Primary energy rate Carbon dioxide emission rate Fabric energy efficiency rate The first two are influenced by both the building fabric and the fuel used within the dwelling. The fabric energy efficiency rate is defined entirely by the building fabric. As we are talking about rooflights, which are part of the building fabric, we won’t be discussing heating systems, different fuel types and building services in this blog post. How can rooflights help to achieve Part L compliance? What does meeting the requirements of Part L look like in practice? Generally speaking, dwellings need to aim for well-insulated and reasonably airtight building fabric. Doing so reduces thermal transmittance and keeps the leakage of warm air to a minimum. Glazing of any type must play its role within the building fabric performance, while acknowledging that it doesn’t perform as well as the surrounding construction in terms of U-values. Ideally, the U-value of windows and rooflights should be as low as possible. This is particularly important to minimise thermal bridging, where the rooflight sits within the roof build-up. Failing to address thermal bridging risks undoing all the intended performance goals for the dwelling. Rooflights must be installed within the surrounding roof, without creating a break in the thermal envelope and causing significant thermal bridging. For the first time, Part L 2021 introduced a requirement for photographic evidence to demonstrate that details were being installed in accordance with the intended design. This effort to reduce the difference between what is designed and what is built on site – known as the performance gap – is vital to ensuring that dwellings do not consume more energy and emit more carbon than anticipated. Using rooflights to go beyond the minimum standard of Part L We’ve already acknowledged that Part L only sets out a minimum standard. The option to go beyond the requirements is always available and can be considered preferable. A frequent criticism of national building regulations, especially in recent years, is that the requirements in one area don’t complement the requirements in another area. The most common example of this issue is how levels of insulation and airtightness have increased, without a corresponding improvement in rates to maintain indoor air quality and reduce. Changes to the regulations are only just beginning to overcome this disconnect. Designers and specifiers of prestigious homes and high-end apartments have it within their power to think holistically and deliver a joined-up approach that benefits their clients and adds value to their projects. The blank canvas of a new project offers the opportunity to deliver more than the minimum standards required by building regulations. Project teams now routinely look to the promised and predicted climatic conditions decades down the line, to benchmark performance now. Rooflights have always played an important role in homes. They can provide a level and quality of daylight that façade glazing alone struggles to replicate. And better levels of natural light are good for the health and wellbeing of building occupants and can reduce reliance on artificial lighting – thereby saving energy.

The rise in homeowners extending their properties has increased alongside a growing demand for suitable rooflights for flat roofs therefore, it is important to recognise that installing a rooflight onto a flat roof is not simply a case of installing a section of glass over an opening. This is of course a quick and easy approach that may provide a solution for a while, but in time common issues will develop that can cause unnecessary damage to your roof and building internals. Such issues can be avoided if you specify the right product for the job. The correct or minimum pitch for flat roof fixed rooflights Although rooflights for flat roofs are now much more readily available, product manufacturers often hear similar questions as to how they should be installed, one of the most common being ‘What pitch do I install the unit at?’ There is no single answer to this question due to product ranges being quite diverse. However there is still a methodology behind it, which this post will discuss in relation to the most straightforward fixed rooflights. For planning reasons and aesthetics, customers often ask if the rooflights can be installed onto a flat roof - It is recommended that regardless of overall dimensions, a minimum 3 degree fall is sufficient to ensure that water will drain off the surface of the glass and avoid ponding, a process in which puddles of water on the glass surface evaporate and leave unsightly dirt and staining on the glass. With a minimum 3 degree fall, individual droplets of water will still stay on the glass as they would on vertical glazing, but larger pools of water will not form. In all glazing there is a degree of deflection that is particularly apparent on overhead glazing. A combination of wind load, snow load and the physical self-weight of the glass all contribute to the amount of deflection that is apparent. The glass rooflight specification should be calculated so that the maximum amount of deflection under the worst case loading and on the largest pane sizes does not exceed 25mm. Without the pitch, any deflection in the glass will increase the severity of water ponding so installing the roof light at a minimum 3 degrees is the recommended method for avoiding this problem. Increasing rooflight pitch to 5 degrees For more efficient results and improved drainage, increasing this to 5 degrees, as shown in the following diagram, can be beneficial; the pitch is constructed by building the required slope into the upstand itself. For pitches greater than 5 degrees, the pitch must be built into the roof with the kerb constructed perpendicular to the roof as illustrated below, otherwise the down leg of the framework may foul the external face of the kerb. This could result in a poor fit that means the rooflight is not properly supported. Specification considerations should also be given to the orientation of the rooflight. For example, if you have specified a unit of 5 m x 1 m, it would be wise to build the pitch into the span dimension; the differential between kerb heights on opposing sides is reduced and water has less distance to travel when running off the unit. Specifying Walk on Rooflights The only real exception to the 3 degree rule is where walk-on specification glass is going to be used; obviously the glass needs to be as level as possible for its chosen application. For walk on use, it is recommended to build a 1 degree fall wherever possible to allow some water run off. The risk of ponding is marginally greater but because walk on glass is so much thicker in order to carry the design floor loadings, the deflections relative to pane size will be far less than with standard double or triple glazing. In addition, since the unit is accessible, the glass can be cleaned far more easily so that water ponding is not so much of an issue. Please note that requirements may vary depending on your chosen manufacturer. Always check that the specification meets your flat roof design. It is also critical to consider your supplier when specifying rooflights for flat roof applications. Due to the minimal pitch used it is important to look in detail at the product and ensure that there is no external capping around the edge of the unit, which could trap moisture and dirt, leaving an unsightly mess.

High-quality residential developments are no longer defined only by their location and standard of finish. Stunning architecture, luxurious interiors and high-end amenities are still expected, of course, but there is something else to add into the mix: sustainability. A new home or high-rise development doesn’t have to be labelled as an “eco home” to be part of the sustainability conversation. Whether driven by the client, the architect, or the two working in collaboration, better standards of energy efficiency and comfort, along with healthier interiors, are now normal aspirations. The blank canvas of a new project offers the opportunity to deliver much more than the minimum standards required by building regulations. Project teams now routinely look to the promised Future Homes Standard – not due to be implemented until 2025 – as a benchmark for performance. As a component of the building envelope that must balance energy efficiency with providing natural light and views out, rooflight specification plays a big part in whether that benchmark is achieved. What is the Future Homes Standard? The Future Homes Standard is the name given to proposed changes to the Building Regulations in England, expected to take effect this year. It is not one single standard or document, but the combined result of updates to Part L (conservation of fuel and power), Part F (ventilation) and Part O (overheating), as part of the wider Building Regulations. The current stated intention of the ‘Future Homes Standard’ is for new residential properties to deliver an average reduction in carbon emissions of 75-80% compared to Part L 2013. Thanks to such significantly better performance, homes should not require energy efficiency retrofit measures in future. The eventual decarbonisation of grid electricity will account for the remaining operational emissions, meaning new-build homes will play their part in helping the country to meet its legally binding net zero carbon targets. How can projects be built to the Future Homes Standard today? Until it is consulted on and agreed, we don’t know the precise technical detail of the Future Homes Standard. However, there are two key elements that make it possible to deliver a new residential development today and claim alignment with it. The first is the knowledge of the intended carbon reductions. A development can be assessed against the version of SAP used by the current Part L 2021, with improvements made to the specification such even greater carbon reductions are demonstrated. The second element is Part L 2021 itself. The government introduced Part L 2021 with the specific intention of it acting as a stepping stone to the Future Homes Standard. It lays the groundwork for increased uptake of heat pumps, and the general electrification of properties, alongside much better building fabric standards. These will all be features of the eventual Future Homes Standard. Specifying rooflights to deliver Future Homes Standard levels of performance  Despite uncertainty around broader government policy, businesses are pushing ahead with their plans to help deliver net zero. The construction industry is no different, and projects are routinely looking to achieve performance above and beyond Part L 2021. Part of that is sensible risk management. Planning a project now to current regulations, only to find it then needs to meet the Future Homes Standard in just a few years, would require substantial changes to the specification. Much better to work to that specification now and create healthier, more comfortable and more energy efficient homes. High standards of building fabric performance, supported by low U-values and correct installation, are essential for meeting current or future regulations. Rooflights are part of the building fabric, so choosing high-quality components from a reliable manufacturer is essential. Rooflights have always played an important role in homes. They can provide a level and quality of daylight that facade glazing alone struggles to replicate. Better levels of natural light are good for the health and wellbeing of building occupants and can reduce reliance on artificial lighting – thereby saving energy. With greater focus on sustainability, installed rooflights must deliver the right thermal transmittance (U-value), solar transmittance (g-value) and, where required, ventilation to support the overall energy efficiency and comfort goals. That is true whether choosing from an existing range or having bespoke items created to fit a particular architectural vision Rooflights also must be capable of being installed within the surrounding roof, without creating a break in the thermal envelope and causing significant thermal bridging. Thermal bridging heat losses risk undoing all the intended performance goals for the dwelling as a whole. With overheating now a part of the Building Regulations, rooflights can play an even greater role. Alongside delivering daylit interiors, impressive views and desirable architecture, they can be positioned to limit solar gains. Their potential to provide natural ventilation might also be an answer in situations – such as high-rise developments – where achieving cross-ventilation through a property is not possible.

With increasing percentages of the working population working in remote or hybrid-remote conditions after the pandemic, the home office is becoming more popular than ever. Working in a comfortable home office is extremely important as it will allow you to be more productive and comfortable in your workspace. An easy way to transform your workspace is by adding a glass rooflight – Unlike regular windows, rooflights allow natural daylight to enter the room from above, making your office feel brighter and more open. The Benefits Of Natural Daylight Ensuring that your home office is well lit, naturally, is essential as natural daylight offers numerous benefits from increased productivity to physical health benefits.  The quality of light in a room can have a profound impact on the level of productivity. Exposure to natural daylight regulates the body’s circadian rhythm (The 24-hour sleep-wake cycle that naturally occurs internally) – The human body is biologically programmed to respond to light and dark cycles, with light being the primary cue for regulating these circadian rhythms. In addition to increased productivity, natural daylight can help enhance mood due to stimulating the release of serotonin, a natural neurotransmitter that contributes to feelings of well-being and happiness. Higher serotonin levels are commonly associated with better mood and higher levels of focus and productivity. The presence of natural daylight during the working day will trigger serotonin production, which can support increased mental clarity, reduced stress, and improved overall mood. As well as the mental health benefits, increased levels of natural daylight can enhance physical health due to the stimulated release of Vitamin D which is essential for maintaining physical health, including bone health and immune function. Installing a rooflight in any room will reduce the reliance on artificial sources of lighting, which can boast numerous benefits. Relying less on artificial lighting increases energy efficiency as the natural daylight will illuminate the space for longer, especially during the summer months. In addition, increased natural daylight reduces eye strain in turn reducing the likelihood of headaches and fatigue Optimise Your Space As well as the profound mental and physical wellbeing benefits of installing a rooflight in your home office, there are also practical benefits. Installing a rooflight will improve the aesthetics of the room, and working in a home office workspace that you are comfortable in will be essential to productivity and mood during the working day. This improved aesthetic appeal could also reap benefits in the future and increase the value of your home and make it more appealing to potential buyers. One of the main benefits of rooflights, aside from the increased levels of natural daylight, is that they can be installed in a room of any size.  Most flat rooflights on the market are specially designed to be installed on a builder’s upstand, meaning that it does not take up valuable space in your home. For example, rooflights like the Glazing Vision Walk-On Flushglaze are the perfect solution for unlocking the possibilities of your roof terrace whilst also allowing natural daylight to flow into the room below. The Perfect Rooflight For You With so many high quality rooflights on the market, it can be difficult to know which glass rooflight is right for you and your specific requirements; whether you require increased levels of natural daylight, ventilation or maintenance access to your rooftop. Choosing a rooflight that suits your unique needs is important, for a home office an increase of natural daylight is essential, however if you would benefit from increased levels of fresh air, especially during the summer months, you should opt for a ventilation rooflight such as the Glazing Vision VisionVent Rooflight which can be effortlessly opened with the touch of a button. If you require your rooflight quickly, our off-the-shelf rooflights are a great option as they can be delivered to you within a working week - Explore our flat rooflights now and receive your desired rooflight(s) in 3-5 working days.

Glass rooflights can have a huge impact on the influence of light in a building. It can be at the heart of the project or complement the space. The choice of options for glass rooflight design are now greater than ever and can be expertly used to bring light, air and space to projects. For residential designs, a rooflight can be used for single property renovations in cities where both space and light are at a premium to glazing solutions, bringing the natural beauty of the outside in. The use of glazing for commercial applications ranges from stunning, light enhancing designs to specialist glass applications. Regardless of the project and inspiration, there are many considerations in the design and specification of glass rooflights: What classification is the rooflight? Where is it being installed? What is the building type? Commercial, residential, public? Glare and solar gain considerations, what glass should you use? What is it being used for? Daylight, ventilation or access? What do you want the rooflight to achieve and what other considerations should be taken into account when specifying? In addition, the following factors should also be considered about the building type and its location within that building: What function does the rooflight perform? Will the rooflight be subject to foot traffic? Will it be positioned where it is subject to high thermal stress? Can something fall on the glass? Is it easy to clean? Will it cause an obstruction to other parts of the building? What preparations should be made to the roof structure in order to adequately support the rooflight? If the rooflight opens, do the electrics and transformers need to be housed within the building fabric? What is the lead time and how may this affect other trades such as plasterers, roofers of electricians? Will any of these considerations affect the glass I need? To understand more about the design and specification of glass rooflights, please contact our experienced team or explore our range of rooflights.

Part F of the Building Regulations in England sets out requirements for ventilation. The current version is Part F 2021, which is expected to be replaced by a new version later this year as part of the overarching Future Homes Standard. Wales and Scotland have their own ventilation requirements, albeit the overall aims across the different countries are similar. Appropriate levels of ventilation protect the health of building occupants by avoiding mould and poor indoor air quality. Achieving the right rate of ventilation is essential for meeting current or future regulations in all parts of the UK. Rooflights have a role to play in ventilation control for dwellings, particularly in terms of providing the option of purge ventilation. What are the requirements of Part F 2021? As detailed in Approved Document F volume 1, Requirement F1 is broken down into two separate aspects. Requirement F1(1) is that there shall be adequate means of ventilation provided for people in the building. Requirement F1(2) is that fixed systems for mechanical ventilation and any associated controls must be commissioned by testing and adjusted as necessary. Ventilation strategies can be delivered by mechanical means, natural means or both. Part F 2021 supports each of those options. Requirement F1(1) is met if the ventilation strategy for a dwelling: Extracts water vapour and indoor air pollutants; Supplies a minimum level of outdoor air; Can provide purge ventilation to rapidly dilute pollutants and disperse vapour; Minimises the entry of external pollutants; and Keeps noise to a minimum, can be maintained and provides protection from cold draughts. How can rooflights help to achieve Part F compliance? High levels of ventilation are good for occupant health, but excessive ventilation increases energy use. When heated warm air is lost – in either a controlled or uncontrolled manner, depending on the quality of the construction – the cold air that replaces it must be heated. It therefore makes sense to avoid extra load on the heating system by making ventilation as efficient and effective as possible. Mechanical ventilation systems providing a predictable, consistent and controlled supply of fresh air are increasingly seen as the preferred solution. Simple extract fans are mechanical, but more sophisticated, whole-dwelling solutions can include heat recovery. That means the warm air extracted from the building is used to heat the incoming cold air, lessening the reliance on the building’s heating system. Natural ventilation is mostly driven by external air pressure and air movement, which can fluctuate and might not be entirely dependable on days when it is most needed. Arguably, natural ventilation should be viewed as a supplement to a mechanical system, to take advantage of the days when it is most effective. Paragraph 1.9 of Approved Document F volume 1 says that whatever solution is adopted for a residential dwelling, the overall strategy should be capable of delivering the following. Extract ventilation in rooms such as kitchens and bathrooms. Whole-dwelling ventilation to provide fresh air and remove pollutants not dealt with by extract ventilation. Purge ventilation to remove occasional high concentrations of pollutants. Extract ventilation is only possible via mechanical means, but rooflights can play a meaningful role in the other two areas of ventilation strategy. Where they really excel is in providing additional options for ventilation control, either in individual rooms or the dwelling as a whole, that may not be possible with façade windows alone. Rooflights are an excellent way of helping to achieve cross ventilation through a property where openings on opposite sides of a building are not available or don’t readily align. Using rooflights to go beyond the minimum standard of Part F Like all areas of building regulations, Part F only sets out a minimum standard. The option to go beyond the requirements is always available and is particularly worth considering when it comes to ventilation. A frequent criticism of regulations in recent years is that requirements in one area don’t complement the requirements in another area. The most common example of this issue is how ventilation rates have failed to keep pace with increased levels of insulation and airtightness aimed at improving energy performance. Without a corresponding improvement in ventilation, indoor air quality has worsened, and overheating risk has increased. Changes to the regulations are only just beginning to overcome this disconnect, with Parts F and O now aligning better with Part L. However, designers and specifiers of prestigious homes and high-end apartments can think holistically and deliver a joined-up approach – possibly by adopting voluntary standards as well – that benefits their clients and adds value to their projects. The blank canvas of a new project offers the opportunity to deliver more than the minimum. Project teams now routinely look to the promised Future Homes Standard, and factor in predicted future climate conditions, to benchmark performance now. Rooflights have always played an important role in homes, providing a level and quality of daylight that vertical windows alone struggle to replicate. And better levels of natural light are good for the health and wellbeing of building occupants and can reduce reliance on artificial lighting – thereby saving energy.

When selecting the perfect rooflight, energy efficiency is a critical factor to consider. Rooflight U-values measure thermal performance, indicating how well the product retains heat and helps reduce energy consumption. Rooflight U-values – What you need to know The thermal performance of rooflights, including the U-value they achieve, is an essential part of building fabric specification. Balancing outgoing heat loss with incoming daylight and solar energy all contributes to the wider sustainability goals of a project – including the overall thermal efficiency of the building, and the thermal comfort of its occupants. Designers and specifiers therefore need to understand what quoted U-values mean, and the relevance of other performance measures such as Ug-values. This post concentrates on how rooflights allow solar energy in and limit heat transfer out. However, for projects where daylighting is just as important a consideration, factors such as light transmittance and reflectivity must also be taken into account. Why can rooflights have two different U-values? Anybody involved with building design and specification should be aware of U-values as a measure of thermal transmittance (the movement of heat energy) through building fabric from warm to cold. The composition of roof glazing units – including overall size, relative areas of glazing and frame, and the thermal performance of the materials used – varies, so U-values quoted in a specification should be based on an actual product or a detailed calculation model. However, performance specifications may not be clear about whether a whole-unit or centre pane value is required. Manufacturers themselves may not be clear about the type of U-value they are quoting, creating the potential for confusion. In most circumstances, U-values should be for the whole unit, including glazing and frame. Whole-unit U-values can be improved through the use of a warm edge spacer. Traditionally, spacer bars are aluminium but, like any metal, aluminium has a high thermal conductivity. It acts as a thermal bridge, conducting heat from inside the building at the edge of the glass and bypassing features otherwise designed to improve the efficiency of the glazing. ‘Warm edge’ spacer bars use materials with a lower thermal conductivity to slow the rate of heat loss and create a more even surface temperature across the whole glass pane. Centre pane U-values address the thermal performance of the glass only. They appear lower than whole-unit values because the cold bridging effect of the spacer and edge seal are not accounted for. Unfortunately, this means some manufacturers rely on quoting centre pane U-values when they should offer whole-unit U-values. Specifiers can find themselves misled if a centre pane value is made to appear as though it is a better performing product. Centre pane values do have an application, though. They are useful for comparing one glass against another when being used in the same frame, as well as in conservation projects where traditional frame designs offer no meaningful thermal performance. Why should you consider rooflight g-values alongside U-values? Compared to the total surface area of the building fabric, the U-value heat loss through relatively small areas of roof glazing is more than offset by the contribution of solar gains and the reduced use of artificial lighting. The measure of infrared radiation (solar heat) allowed into a building is the g-value. A g-value can be anything from 0 to 1, where 0 represents no solar heat gain and 1 is the maximum possible solar heat gain. It is calculated by dividing the total solar heat gain by the incident solar radiation (the amount of solar radiation received on the surface during a given time). The lower the g-value, the lower the percentage of solar radiation allowed through the glass. Like U-values, performance figures can be quoted for the glass alone or for a complete glazed unit. Better, lower g-values also result in lower light transmission. How do different gases change the thermal performance of rooflights? Most people understand the benefits of having a glazing unit that is more than just single glazed. Double glazing, triple glazing and even quadruple glazing improve the thermal (and acoustic) performance by introducing sealed layers of gas between the panes. A well-known feature of products is to fill the sealed space between panes with an inert gas like argon, whose thermal conductivity is some 34% lower than still air. Some manufacturers use krypton and xenon, both of which offer further improvements in thermal efficiency, but which are more expensive. Do low emissivity coatings impact on rooflight U-values? The function of low emissivity (low-e) coatings is to impact on the loss of solar radiation back out of the building. A material’s emissivity determines the amount of thermal radiation emitted from its surface. Low-e surfaces emit less thermal radiation, and glazing units benefit from this through the application of a microscopic coating of tin, silver or zinc to certain faces of the glass panes in the unit. In contrast to the short-wave radiation from the sun that heats the building interior, the heat energy transferring back through the building fabric, from warm inside to cold outside, is long wave radiation. Glass with the low-e coating reflects long wave radiation, effectively keeping more heat energy in the building. There are two types of coating: hard and soft. Hard coat is applied while the glass is still molten, whereas soft coat is applied later in the process. Hard coat is more durable, as its name suggests. Soft coat remains delicate, is only applied to the sides of panes facing into a sealed airspace, and has a lower emissivity than hard coat. The difference in emissivity between the two means argon-filled glazing with a hard coat treatment will typically offer a centre pane U-value of 1.4 W/m2K, while a soft coat treatment will see that improved to 1.1 W/m2K. It’s a meaningful distinction, yet some manufacturers will simply claim their glazing to be “low-e”. Making a hard coat treatment sound like a similar benefit to soft coat is another reason for specifiers to be clear about the features of the products they’re selecting.

Rooflights and roof windows are both popular choices for bringing natural daylight into a property, and rooflights can also provide a variety of other benefits, such as natural ventilation and access to roof terraces. When selecting a roof window or rooflight for pitched roofs, there are several specification considerations to think about – and one factor that could play an important part in your decision is the pitch of the roof. Roof pitch affects drainage, determines how the units should be installed and even what type of products you can use. Below, we explain the different requirements for rooflights and roof windows; this should help you to decide which product is most appropriate for your project. Installing a rooflight on a flat roof When installing a rooflight on a flat roof you should ensure that the product is not fitted completely flat itself. Glass inherently has a degree of flex when installed flat (as opposed to vertically as you would find in traditional windows and doors). This is known as ‘deflection’ and means that without pitching the rooflight up slightly at one end, rainwater will accumulate and begin to ‘pond’ on the glass. When this evaporates it can leave unsightly marks and stains behind. Manufacturers therefore recommend a ‘minimum pitch’ to install their product so that rainwater and debris runs off the glass more effectively, keeping the rooflight cleaner for longer. The recommended pitch for rooflight installation on a flat roof For many rooflight applications on flat roofs, there should be a minimum pitch or fall of three degrees. This is enough to ensure that water will drain off the surface of the glass and avoid ponding. The higher the pitch, the more effective it is at draining off the water, so although three degrees is often the recommended minimum pitch, installing the unit slightly higher – for example at five degrees will prove more efficient. To achieve the required pitch, an upstand or kerb is usually constructed around the aperture in the roof, which will accommodate the slope into it for the rooflight to be structurally fixed to. If you are unsure, the rooflight manufacturer should provide drawings to indicate minimum kerb heights, which will allow your builder to calculate how high the top of the slope needs to be to achieve the desired pitch. Steeper pitches for rooflight installation on flat roof Rooflights can be successfully installed at steeper pitches, but for flat roof applications the height at the top end of the upstand will begin to be so great it will compromise aesthetics and potentially contravene planning permissions, which in some cases will limit the height of any structure that can be built above roof level. Depending on the rooflight design, installing on more harshly pitched upstands may result in fouling the framework, so you should always check with manufacturer drawings and recommendations prior to commencing works on site. Other considerations for roof pitch and specification Here are a few more things to think about in relation to roof pitch and specifying rooflights for pitched roofs. ● Deflection – There is a level of flex that will occur in all glazing – and it can be particularly apparent in overhead installations. Wind loads, snow loads and the weight of the glass itself can contribute to the amount of deflection, and this can hinder drainage. ● Orientation – Pay attention to the orientation of the rooflight so that you can maximise. For example, if a unit has a 5m width and a 1m span, it’s better to build the pitch into the span dimension so the water has less distance to travel. ● Capping – Because rooflights have minimal pitch, it’s a good idea to check products closely to ensure there is no external capping around the edges. This is because capping can trap moisture and dirt, which can result in unsightly messes and damage to the unit. The correct pitch for installing a roof window on a flat roof Unlike rooflights mounted onto an upstand, roof windows are installed in-plane, meaning they follow the pitch of the roof and are mounted flush with the surface. Answering the question: “What’s the minimum roof pitch for a roof window?” is also much easier to answer. Because the units follow the existing roof pitch they do not require any additional height at one end to allow for drainage. According to EN 14351-1:2006, roof windows should be installed on roofs with a pitch of at least 15 degrees. Roof windows should be CE marked against this standard. Rooflights, however, cannot be CE-marked because they are usually installed ‘out of plane’ on an upstand and are not considered roof windows. Please note that specific requirements may vary depending on the manufacturer. Always check that the specification meets your roof design.

Glass can become slippery when wet and common sense should be applied when specifying this material for walk-on applications such as walk-on rooflights. This is of particular importance when the glass is being installed where the public can access it. In a private dwelling it is less likely that the glass will be used if it is raining, but the same cannot be said for commercial and public applications. Applying an anti-slip glass surface finish to glass that is designed for walk-on applications should always be considered; the same finish can also provide some obscurity to the glass if required. A screen printed frit that includes particles within the ink to create a rough texture can be applied to the glass in a variety of patterns, which will significantly increase the slip resistance of the glass. Alternatively the surface of the glass can be sandblasted which will result in more diffused light and improved obscurity. Slip resistance is measured using mean Pendulum Test Values (PTV); the higher the figure the better the slip resistance. A PTV of 0-24 has a high slip risk, 25-35 has a moderate slip risk and 36+ has a low slip risk. The test is carried out in wet and dry conditions and the lowest figure is obtained when wet. Generally sandblasted glass achieves a PTV of 50 and fritted glass achieves a PTV of 60, providing better slip resistance than the sandblasted. However both are well above the threshold of 36 to be categorised as having a low slip potential.

We all have a predilection to well lit, inviting spaces, so increasing the use of glazing products in the built environment is almost always an efficient way of improving an internal space. But what is the difference between these glazing products: is a skylight window different to a rooflight, or a rooflight different to a roof window? There are plenty of benefits to bringing natural light into a building – from boosting occupants’ wellbeing, through to saving energy. Roof windows, rooflights and skylights are all popular options for letting the sunshine in and improving the look and feel of an internal area, but what’s the difference between these products – and how do you know which one is the right choice for your project? Is it A Roof Window, Rooflight or Skylight? It’s fair to say that the terminology used to describe glazed units in roofs can be a bit tricky to understand – so don’t worry if you’re not sure what the difference is between roof windows, rooflights and skylights. It’s also fairly common to see terminology being used inconsistently, which increases confusion. Let’s take a look at each product type to help clear things up. What are roof windows? These are probably the easiest to define because they are covered under BS EN 14351-1:2010. The standard stipulates that roof windows must be installed in the same orientation and ‘in plane’ with the surrounding roof, typically at a minimum 15° pitch. Once installed, they should be weatherproofed using a skirt or flashing. Roof windows must be UKCA marked before they can be sold and manufacturers are expected to provide a declaration of performance (DOP) to advise specifiers how each unit performs under test conditions. Typically, this will cover things such as tests to simulate prolonged and heavy rainfall, how the roof window withstands increased air pressure, glass deflection and monitoring any air leakage to ensure the product does not create drafts or allow in damp. Roof windows are usually only available in standardised shapes and sizes and are typically smaller than rooflights. However, new products have recently become available using improved glass specifications that allow much larger sizes to be manufactured. Rooflights.com stocks the sleek Glazing Vision Pitchglaze Roof Window which is a fixed roof window that can be installed in roof pitches between 15° and 60°, it offers completely frameless internal views. What Are Rooflights? ‘Rooflight’ is a generic term that can sometimes mean different things. Typically, the term refers to a glazed unit installed on a flat roof, or where installed on a pitched roof it is likely to be fitted ‘out of plane’ with the level of the tiling. Rooflights are commonly installed using an upstand or kerb system to support the actual product and act as a surface for any weathering to be fixed to; on flat roof systems the upstand will provide enough height to ensure that the rooflight remains watertight. The rooflight quite often has to be installed at a certain height to maintain any guarantees supplied by suppliers of waterproofing systems. Rooflights come in a huge range of designs and styles, and as well as providing natural light, they’re also often used for ventilation or access. Options include frameless fixed rooflights, which offer a minimal appearance and sky-only views, such as the Glazing Vision Fixed Flushglaze Rooflight. Other rooflight options include hinged rooflights, sliding rooflights, fire rated and AOV rooflights, and box rooflights, which are often used to provide access to roof terraces. What Are Skylights? Skylight is another generic term, and it’s often used by manufacturers for a variety of different products, ranging from small-scale domestic units installed on traditional pitched roofs to larger bespoke glazed units designed to be installed on flat roofs or terraces. Skylight is a generic term that can sometimes confuse consumers, since the products it refers to may differ quite drastically in terms of size, scale, function and application. In some cases, the use of the term skylight is actually completely inaccurate as far as the Building Regulations are concerned, where more appropriate terms should be used that are recognised in British Standards. Specification Considerations: Advantages and Disadvantages In most cases, choosing between a roof window or rooflight (or skylight) is easy: if it’s going on a pitched roof, you’ll want a roof window; and it will be rooflights for flat roofs. However, there are other issues to think about. Off-the-shelf design vs customised Roof windows are very popular and widely used having been adopted by many major national house builders. They are robust, reliable and offer value for money. The advantage of standardised sizes and specifications means that they are usually available to buy ‘off the shelf’. The disadvantage of this is their flexibility – particularly when it comes to scale. If you’re looking for larger sections of glazing on your roof then roof windows presently only offer a limited amount of scope. Rooflights (or skylights) tend to be offered in a much wider range of shapes, sizes, specification and function. However, they tend to be more expensive than roof windows due to their bespoke nature, and since they are usually built to order, there will be a lead time of several weeks. External appearance Rooflights and roof windows are both available in frameless designs, which means you only see glass when looking up at the unit from indoors. However, these products look quite different from the outside. Since roof windows are designed to sit flush with the plane of the roof, they offer aesthetically pleasing clean lines, which rooflights sometimes struggle to match. That said, rooflight manufacturers are beginning to respond to client demands for the flexibility and scale of a rooflight, but with a low external profile that can be installed flush with roof tiling lines in the same way that a roof window can.

Glass, when installed overhead in rooflights and skylights must be ‘safety glass’, which is often referred to as Toughened or Tempered Glass. Toughened glass is 4-5 times stronger than standard annealed glass of the same thickness; it’s a key safety feature in the specification of domestic rooflights and skylights as it is designed to crumble into granular type fragments when broken, rather than shatter into jagged shards like annealed glass. This significantly helps to reduce the risk of injury. How is Toughened Glass Made? Toughened glass is produced by passing annealed glass through a furnace, heating it to above 600°C before being rapidly cooled. A balance of high compressive stresses at the surface and tensile stresses in the centre of the glass increase its strength. When the glass breaks it is the release of these stresses that causes it to break into small pieces – usually accompanied by a large bang as the energy is released. Toughened (tempered) glass is a preferred option for rooflights but there can be disadvantages. Firstly, glass needs to be cut to the required size and shape before it’s treated. Secondly, toughened glass has been known to spontaneously fracture for no apparent reason with the most likely culprit being Nickel Sulphide (NiS) inclusions within the glass. NiS is a chemical contaminant that can manifest itself during the toughening process; as it gradually changes state over time it can cause the glass to fracture. This can happen at any time, from a few weeks to many years or not at all. One of the most effective ways of combating this is to subject the glass to 'Heat Soak Testing'. What is Heat Soak Testing? Heat soak testing is carried out during the manufacture of the glass and will filter out around 95% of problem units. This involves heating tempered glass up to 290 degrees Celsius and holding it at that temperature over a controlled period of time. This process accelerates any NiS inclusions reverting back to their Beta state, which could result in glass failure. Whilst more expensive, this method of testing identifies any issues with toughened glass before it’s used in manufacture. This is of particular importance when specifying larger structural rooflights or those used for walk on applications, where heat soak testing is a requirement of Building Regulation. What is Laminated Glass? Annealed laminated glass can also be specified for some rooflight applications, to conform to BS5516 Part 2 – pane sizes above 3m2 and between 5mts and 13mts from floor level should be laminated. Laminated glass is produced by combining two or more sheets of float glass with one or more interlayers. Glass integrity is maintained from a ‘laminated’ interlayer, commonly PolyVinylButyl (PVB), which is processed with heat and pressure under factory conditions. Should any damage occur, the interlayer holds any fragments together preventing them from falling, reducing injury risk even further. Combinations Toughened Laminated or HST Toughened Laminated are also common glass specifications, particularly when the glass has to perform a structural function, as in a glass floor or structural glass fins.

Rooflights are versatile construction products, available in pitched rooflight and flat rooflight variations to provide daylighting solutions in a whole host of roof constructions. They can flood homes and apartments with natural light while contributing to the energy efficiency requirements of Part L, providing ventilation and combatting overheating, and having stunning aesthetics – possibly through visual effects. To do some or all these things means specifying glass in the rooflights accordingly. Maybe a pitched rooflight requires solar control, or a flat rooflight needs to be safe to walk on. To meet the different performance requirements demanded by modern construction projects requires more than just standard glass, and this blog post gives an overview of some of the available variations. What Heat-treated Glass Types are used in Rooflights? Annealed glass is free of internal stresses caused by other heat treatments, but it breaks easily into large shards and is considered unsafe for certain uses in buildings. Annealed glass can be used as safety glass when it is incorporated into a laminated pane but the risk of thermal heat stress should be considered. This can be caused by partial shading from external objects or close-fitting blinds on the inside of the glazing. Thermal stress in glass can lead to thermal cracking of the glass. Toughened glass is a product that breaks into smaller pieces or granules, and is therefore considered a safety glass. It is produced by rapidly cooling annealed glass to make the surface of the glass more resistant to tensile failure. This tempering makes toughened glass some five to six times stronger than annealed glass, and more resistant to blunt impact. Heat-strengthened glass is tempered in a similar way but cooled more slowly. It is only around three times as strong as annealed glass (or half as strong as toughened glass). If it breaks, it exhibits similar behaviour to annealed glass. It cannot be used as safety glass on its own but does lend itself to use in a laminated pane. Bonding two panes of glass with an interlayer produces laminated glass, a catch-all term to cover the various combinations of glass and interlayer. Because the interlayer holds the glass even when broken, laminated glass is typically used where security is a priority, as well as in safety applications like overhead and walk-on glazing. Another advantage of laminated glass is that it offers an acoustic performance benefit. Read more about the differences between toughened and laminated glass. Considering the issue of safety further, most rooflights are designed to be non-fragile, and to provide a level of non-fragility equivalent to the surrounding roof. They should not be taken as being safe to walk on, instead being designed typically to prevent people or objects falling through in the event of an accident on the roof – unless specifically designed for floor loadings. For overhead glazing the first choice for the inner pane should always be a laminated glass to ensure it is considered non-fragile and to protect building occupants below from falling glass shards if a pane should ever fail. What Other Specification Options are Available for Rooflight Glazing? As part of contributing to the thermal efficiency of the building fabric, the glass in rooflights can be treated to provide solar control and reflectivity. It can also receive a low emissivity (low-e) coating to allow short-wave radiation from the sun into the building while restricting the loss of long-wave radiation back out of the building. However, these options are not different types of glass, they are treatments and coatings applied to the chosen glass. A development that does fall into the category of a different ‘glass type’ is heated glass. For applications where the moisture load/humidity is particularly high (such as swimming pools), heated glass raises the surface temperature of the rooflight, reducing the potential volume of condensation occurring on it. Other uses for heated glass include evaporating rainwater or dew and melting ice and snow. When wet, however, walk-on rooflights are slippery, and anti-slip finishes provide an antidote to the inherent risks. Sandblasting the surface of rooflight glass is one way to increase slip resistance, while also adding obscurity and creating light diffusion. More commonly, ceramic frit is used. Modern techniques screen-print the frit onto annealed glass before tempering it to achieve the desired performance. Fired permanently into the surface of the glass, the frit provides the slip resistance. Textured glasses offering slip resistance are also available. Ceramic frit and screen-printing techniques can be used for decorative effect as well, especially in conjunction with enamelled glass. Ceramic paint is applied to the glass before toughening, and the toughening process fires the paint into the surface of the glass. Using enamelled glass in conjunction with LED lights can create striking patterns of colour and light in the glass. These decorative uses of glass, and other situations where clarity is particularly desirable, lend themselves to the use of low-iron glass. The silica used in the initial glass production is selected for its low iron content removing the natural green-blue colouring that occurs otherwise. Other visual effects can be achieved using switchable or electrochromic glass. Switchable glass turns from opaque to clear when a current is passed through it, while electrochromic glass darkens to provide solar control when a current is passed through it. Are There Low Maintenance Glazing Options for Rooflights? As part of the specification process for rooflights, operational treatments can be requested that reduce the maintenance burden for homeowners. Suited to glazing installed at a 30-degree pitch or greater, self-cleaning glass features a coating that organically breaks down dirt, leaving it ready to be washed away during the next rain shower. As self-cleaning glass is not compatible with silicone, an alternative is the proprietary glass treatment, Enduroshield, which acts like a ‘non-stick’ frying pan coating. Whichever option is chosen, periodic cleaning by building users is still required and recommended.

Rooflights featuring toughened or laminated glass, or both, have different applications in construction projects. Broadly, toughened glass provides superior strength, while laminated glass offers better security as it is designed to remain intact when broken. For rooflights designed to take foot traffic, our view is that the outer pane should be toughened, heat soak tested and laminated. When ‘basic’ float glass is annealed, it produces glass that is free of internal stresses caused by other heat treatments. However, annealed glass breaks easily into large shards. That is considered unsafe for certain uses in buildings, and toughened glass and laminated glass are both ways in which float glass can be treated to improve safety. What is Toughened Glass? For a product that breaks into much smaller pieces or granules, and is therefore suitable for safety applications (including overhead rooflights on pitched or flat roofs), toughened glass must be used. Annealed glass is heated, then rapidly cooled to make the surface of the glass more resistant to tensile failure. Glass cracks due to failure at the surface. The tempering balances compression at the surface with tension in the centre of the pane, making toughened glass some four or five times stronger than annealed glass, and more resistant to blunt impact. Toughened glass cannot be cut or worked, so all processing has to be carried out prior to toughening. As it is resistant to large and variable changes in temperature, toughened glass is suited to spandrel panels where there is a risk of thermal cracking. It also offers good resistance to wind pressure on tall buildings and, in particular, corners. Something to consider is that the heating and cooling cycle required to produce toughened glass causes optical distortion in the surface. When annealed glass is heated again, it sags slightly between the rollers carrying the glass through the furnace; the subsequent cooling results in ripples, or ‘roller wave distortion’. Roller wave mainly shows up in the reflections of the glass, and eliminating such distortion entirely is impossible. It can only be reduced, mainly by design and control of the manufacturing process and the way in which the glass is heated and cooled, and moved through that sequence. Thicker panes of glass generally remain flatter, while larger panes typically show up more distortion. Why Does Toughened Glass Benefit From Heat Soak Testing? Spontaneous fracture is known to occur in toughened glass, due to the stabilising of nickel sulphide (NiS) present in the material. The risk of breakage is relatively low, but unpredictable – it could occur within weeks or years of manufacture, if at all. Heat soaking filters out about 95% of potential problem units. Toughened glass is heated to 290°C and held at that temperature, accelerating the process of any nickel sulphide inclusions reverting to their ‘beta state’ and causing failure. Inevitably, heat soaking adds cost but improves product quality and consistency, reducing the use of potentially faulty glass in the manufacture of rooflight products. The use of heat soak testing is not regulated, but reputable manufacturers are more likely to undertake it than not – especially for large structural rooflights or in walk-on applications.  Heat soak testing is not a guarantee that glass will remain failure-free, so manufacturers will not accept any claims for spontaneous failure, but it does reduce the instances of potentially faulty glass entering the supply chain. What is Laminated Glass? Bonding two panes of glass with an interlayer produces laminated glass, a catch-all term to cover the various combinations of glass and interlayer. Because the interlayer holds the glass even when broken, laminated glass is typically used where security is a priority, as well as in safety applications like overhead and walk-on glazing. By far the most common interlayer is polyvinyl butyral (PVB). Ethylene-vinyl acetate (EVA) is also popular; other interlayer materials include cast-in resins, polyurethanes and ionoplast materials. Where transparent plastic materials, like PVB and EVA, are used as the interlayer, the bond is achieved through the application of heat and pressure in a controlled environment; however, plastic interlayers make cutting difficult. Resin is a more versatile adhesive and allows for the production of curved laminates. Demanding performance specifications are driving the development of interlayer solutions, some of which fail to offer adequate levels of adhesion. Manufacturers of proprietary interlayers, such as ionomer-based ionoplast, claim improved performance for especially demanding applications. PVB, however, remains the popular option. 

Rooflights are a great way to bring natural light into your home and creating a more open feel. At Rooflight.com, we pride ourselves on stocking high quality rooflights that look great and last. If you want to keep them performing at their best then you need to regularly maintain them. Here are some simple tips to help you maintain your rooflight in excellent condition. 1) Clean your rooflight regularly Dust, dirt, and debris can build up on rooflights, which can reduce the amount of light they let in. This build up can make your rooflight appear dull and block a large amount of natural daylight, which will effect both energy efficiency and brightness. Over time, accumulated dirt can cause small abrasions on the glass, such as small scratches form fine debris like sand or grit, which may lead to more frequent cleaning requirements. If you want to avoid these abrasions, you need to make sure to use soft cleaning tools and rinse off loose dirt with water before wiping the glass surface. If you want your rooflight to keep looking and functioning at their best the you should clean it every 3-6 months.Safe cleaning methods: You should avoid harsh chemicals such as ammonia based cleaners or bleach, as they will damage the glass coating and seals. Instead, you should use mild soap, water, and a soft cloth to protect the glass and frame.Safety first: If your rooflight is accessible from the inside, you should clean it safely form within. For external cleaning, you should use a sturdy ladder, wear non-slip shoes and always avoid learning too far. You should always make sure that someone is nearby for assistance if needed. 2) Inspect for damage You should be regularly inspecting your rooflight for signs of damage, such as cracks, corrosions or sealant issues. By doing this it can prevent minor problems form becoming major repairs.Glass check: You need to look for three common types of cracks:1) Stress cracks: These are thin, hairline cracks that usually run across the glass in a straight line. They are often caused by rapid temperature changes, particularly when the weather quickly shifts from hot to cold, and they appear without any external impact.2) Impact cracks: These typically look like a starburst like crack that radiate from a central point of impact. They result from a direct force such as something hitting the glass, and show multiple lines spreading outwards from where the impact occurred.3) Edge cracks: These are cracks that appear along the edges of the glass, which is often the result of improper installation, frame pressure, or shifting of the rooflight. They usually start at the border and can extend inward, creating a jagged or uneven appearance.You should inspect particularly near edges or corners, as these areas are most susceptible to damage. If you notice any issues, you need to address them as quick as possible to try and avoid leaks.Frame and Sealant: You need to inspect the frame carefully for signs of corrosion, warping, or rust. Look closely at the joints and corners, as these areas are prone to moisture buildup. Check the sealant for any cracks, gas, or peeling, which could compromise the watertight seal. You should be looking for discoloration, bubbling or any parts where the sealant has pulled away from the frame. If you find any issues, you need to take action to either reseal or repair immediately to prevent leaks and additional damage. 3) Ensure proper drainage Proper draining is the key to preventing water damage, especially for rooflights on flat roofs is by having effective drainage. To ensue efficient drainage, you should:Clear gutters and drains: You should be keeping your gutters and drainage areas free from leaves and debris. To carry out the maintenance safely, ensure you are using a sturdy ladder and gloves for protection, you should also use tools like a gutter scoop that can help you to remove leaves and dirt. After the cleaning is done, you should use a garden hose to flush out any remaining buildup to ensure proper water flow.Prevent water pooling: Water pooling refers to standing water that accumulates on the roof when it is unable to drain properly. This can lead to structural damage and leaks. Rooflights.com products integrate seamlessly with your roofs drainage system, but regular maintenance is important to ensure gutters and drainage paths stay clear. You need to check for blockages or improper slopes that might prevent water from draining efficiently, particularly after heavy rainfall. 4) Monitor Condensation Excessive condensation can be a indicator of poor ventilation or a broken seal. To address this issue, consider the following steps:Ventilation Solutions: Good ventilation can help reduce condensation. To be able to improve your ventilation you can use trickle vents, this is where a small amount of air circulates even when the rooflight is closed, or you can just consider rooflights with integrated ventilation systems. Rooflights.com offers options to improve airflow, such as models with built-in vents or electronic opening mechanisms, this can help maintain the moisture levels in your space.Glazing Issues: If you notice condensation between the glass panes as a cloudy or foggy appearance that doesn't wipe away from either side of the glass then this indicates a broken seal and a loss of insulating gas. If you see this, it may indicate that it time to replace the glazing to maintain energy efficiency. Why choose Rooflights.com? At Rooflights.com, we offer Glazing Vision rooflights that are designed to be easily maintained and built to withstand the elements. By carrying out regular cleaning and inspections it will ensure your rooflight will continue to fill your space with natural light whilst staying energy efficient and leak free.

Adding a rooflight to your home can unlock its potential through increased natural daylight and ventilation and you can install a rooflight yourself, however, it requires extensive prior planning to ensure a seamless installation, with everyone on site remaining safe. Choosing The Right Rooflight Choosing the perfect rooflight for your home will depend on your unique requirements; do you require increased ventilation? Or are you looking to access your roof for maintenance? There are various factors that affect the type of rooflight that you will purchase; from the size of the room to the glazing material that you desire. For more guidance on selecting the right rooflight for your requirements, please read our comprehensive ‘How To Pick Rooflights’ blog. Make Safety A Priority When installing a rooflight, you need to ensure that the safety of everyone on site is of utmost priority, installing a rooflight will involve working at height therefore precautions need to be taken to ensure safety. First, you need to assess if the site area is actually suitable for an installation, if the area is constricted and suitable access is not possible, you should strongly consider installing the rooflight on a more accessible area of the roof. If this is not feasible, you should contact an experienced contractor who will have access to the necessary equipment to reach the area such as cherry-pickers and scaffolding. Prior to commencing the rooflight installation, you need to undertake a comprehensive risk assessment to identify all potential risks and take steps to mitigate these risks. Potential risks that could be identified include manual handling and fall from heights. Many risks are not able to be completely eradicated, but you can take steps to mitigate the risk.For example, the risk of manual handling can be reduced through the use of mechanical lifting equipment, the use of the equipment reduces the need for people on site to manually lift the rooflight as this could lead to injury. Care should be taken at all times when on site to ensure the health and safety of all people present, and site housekeeping on the day is important; cleaning up any spills when they occur, wearing the correct PPE (Personal Protective Equipment) and halting works if weather conditions become too volatile. Understand Building Regulations Before commencing the installation of your rooflight, you should ensure that you have read and understand the relevant Building Regulations (Building Regulations will differ whether you live in England, Scotland or Wales)   Adhering to Building Regulations is a legal requirement as they are in place to ensure the health and safety of people in and around all types of buildings (residential, public and commercial). Adding a rooflight to your home will require your roof to be changed significantly to accommodate the extra weight that the product introduces, and your chosen rooflight needs to provide sufficient insulation against heat loss once installed.It is also important that you apply for planning permission, should you need to. Planning permission is not commonly required for rooflight installation as it falls under “permitted development” however you are required to apply for planning permission if you live in a conservation area or if your desired rooflight is going to protrude more than 150mm above the existing roofline. Gather Necessary Tools & Materials Before undertaking your rooflight installation, ensure that you have all required tools and materials prepared on site. Common tools used for a rooflight installation include a drill, screwdriver, tape measure, and sealant/roofing adhesive. You should check the manufacturer’s installation instructions to see if there are any specific tools or materials required for installation. Prior to commencing the rooflight installation, you should inspect your rooflight for any damage obtained in transit. If you detect any damage, you need to inform the rooflight manufacturer as soon as possible so a replacement product can be arranged. Many manufacturers have a set time period in which they need to be notified of any damage, if you surpass this date, your product may not be eligible for a return or refund.   Prepare The Roof Opening Before constructing your upstand and preparing the surrounding area for installation, you first need to assess the structural integrity of the roof; is it strong enough to carry the additional weight of a rooflight? If your roof is deemed unsuitable in its current state, you can take measures to reinforce the framework such as adding additional wooden framing to boost the roof’s structural integrity. You will also need to address any existing cracks or leaks prior to installation as this will compromise the water tightness of your new rooflight.Most rooflights on the market are specially designed to be installed on a pre-built upstand, these are normally constructed by experienced builders prior to the day of installation. Different rooflights will have differing upstand requirements therefore it is important to read your manufacturer’s documentation to ensure that your upstand is constructed correctly.Thoroughly reading your documentation is crucial as rooflight manufacturers may opt to reference varying ‘critical dimensions’. For example our Flushglaze Flat Rooflight is specified using the External Weathered Kerb dimension, therefore this dimension is the dimension that you should have your upstand constructed to. However, rooflights can sometimes be specified by the critical dimensions of Internal Viewable or Structural Opening, you should always check your dimensions with your manufacturer to mitigate expensive, last minute changes on site. When installing your rooflight, it is important to ensure that the roof is clear of any debris or instructions as this will hinder the installation process and it may also compromise the water and weather-tightness of the product, which could lead to costly repairs in the future. Install Your Rooflight When you are ready to install your rooflight, after addressing any risks present on site and inspecting your rooflight for any damage, you should enlist the assistance of mechanical lifting equipment to lift your product onto the roof and carefully maneuver it into place, manually handling a rooflight is not recommended due to the risk of injury. During installation, you need to closely follow the installation instructions provided to you by your rooflight manufacturer as not adhering to these could lead to a faulty installation. Not adhering to the instructions set out by the manufacturer could also void your product warranty.Your instructions will also outline any specialist tools or materials required to install the product, so you should ensure that you read all documentation prior to commencing the installation on site. Different types of rooflights will have varying installation procedures, for example, opening rooflights are more complex to install than fixed rooflights as there are complex electrics involved. Whilst it is not a legal requirement to have your opening rooflight wiring completed by a qualified electrician, we strongly urge you to enlist their services as this will achieve the optimal installation result and reduce the risk of electrocution for those not acquainted with working with electricity. Test For Functionality Once your rooflight has been successfully installed, you need to inspect the product and surrounding roofing to ensure that there are no gaps or leaks as this will compromise your installation, leading to costly damage in the future. If you have installed an opening rooflight, you need to test all mechanisms to ensure that they are operating how they should. If any issues arise, address these promptly, and if you are unsure, refer to your manufacturer’s instructions or contact them for assistance. Enjoy Your Rooflight Now that you have installed your rooflight, adhering to health and safety guidelines and Building Regulations, you can enjoy the numerous benefits that rooflights offer such as increased natural daylight and improved levels of ventilation. All reputable and trustworthy rooflight manufacturers will offer a period of product warranty on their rooflights, therefore you can enjoy your rooflight for years to come.So, the answer is yes, you can install rooflights yourself however we urge you to thoroughly consider factors such as site access, health and safety of site members and the use of mechanical lifting equipment. The health and safety of site members needs to be your top priority.rooflights.com has been supplying the UK’s builders with high quality rooflights and roof windows for a decade, reach out to our experienced team today to discuss your requirements and get the answers to your rooflight/roof window questions.

You have decided that you want to construct an extension on your home, but where do you start? With so many intricacies when building an extension, it can be overwhelming when starting your project. Whether you are expanding your living space or adding a new office, incorporating rooflights can transform your home through increased levels of natural daylight. Read this blog to understand everything that you need to consider prior to building your home extension. With the mantra of “Don't move, improve” ever-increasing in popularity, many people are opting to build an extension to meet their updated requirements rather than moving to another home. This is because extensions are completely flexible in terms of their applications; they can be used to facilitate extra bedrooms for a growing family or they can host a “home office” for people working remotely. With the large expenses associated with moving house, such as legal costs and stamp duty, it is no surprise that more people are choosing to build extensions. What Are Your Requirements? Building an extension can turn your current home into your dream home, and identifying why you require an extension will allow you to correctly design and budget your project. The main benefit of constructing a home extension is the complete flexibility; you are able to tailor the extension to your unique requirements. Some projects will require a larger budget than others, for example implementing an ensuite bedroom may incur more costs than a simple, home office, therefore you need to factor in all of your requirements when budgeting your extension project. Is The Project Viable? Following on from our last point, you need to assess numerous factors such as budget before planning your extension project. The first factor to consider is the timeline, depending on the desired application of the extension, construction timelines can vary greatly. You need to decide how long you are comfortable with building works taking place at your property as this will dictate how much can be achieved in your desired timeframe. The next factor to consider is the suitability for you and your family whilst the building works are taking place; many families opt to move out whilst the works are taking place due to the disruption, lack of water and electricity, and noise occurring throughout works. You will need to factor the cost of rent into your budget, if your budget does not facilitate this additional cost you could consider staying with friends or family or remaining in the property in selected rooms, your builder will be able to inform you of any water/electricity outages for forward planning. Similarly, you should carefully consolidate your budget to ensure that your project does not over run your funds. Building an extension can incur numerous costs such as professional fees, materials, and more. It is important to note that you need to inform your home insurance company of your changes; building an extension will typically increase the rebuild costs of your home if the worst was to happen therefore your insurance company may raise your premium, so you should factor this into your budget. Hire The Right People Hiring the right people for the build of your house extension will save you costly replacement work in the future, so you should ensure that you carefully research your local builders and check their reviews, this will ensure that your builder has a good track record and is trustworthy. You should use a trade professional database such as CheckATrade to ensure that you are dealing with a reputable and trustworthy builder. CheckATrade scrutinises that traders pass up to 12 checks before joining the database, allowing only quality tradespeople to join their database. Building Regulations & Planning Permission Due to permitted development rights, you will not be required to apply for planning permission for single-story or conservatory extensions unless any of the following factors apply to you: You live in a listed building Your home is located in a conservation area Your home is under a Article 4 Direction There are certain circumstances when rear, side and front extensions require planning permission, so you should check with your Local Authority as to whether you need to apply for planning permission. Even if you do not have to apply for planning permission, your project must meet Building Regulations, this is a legal requirement set out by the UK government. Building regulations will cover all aspects of the extension build from external walls to floors and drainage to doors and windows. If you are carrying out building works near or on a wall shared with your neighbour, you will need a Party Wall Agreement. You are required to inform your neighbour of any building work that you want to execute near or on your shared boundary. You must give your neighbour notice between 2 months to a year before you plan to commence building works and any agreement reached should be in writing. You are required to pay for any building works that you start on a party wall, your neighbour is not obliged to pay just because they agreed to the works. Lighting Your Extension You should give careful consideration to how you will light your extension. Rooflights are ever-increasingly being used to illuminate extensions through an increase of natural daylight, alleviating the reliance on artificial lighting. Glass rooflights are an effective way at increasing the levels of natural daylight in your extension whilst adding an aesthetic touch. An increase of natural daylight can go a long way in boosting the mood of inhabitants in addition to increasing productivity, this is why many of our clients opt to install their rooflight in a home office. Rooflights can be incorporated to suit various applications, with many options available on the market. If you are planning to utilise your extension for a kitchen or bathroom, you may opt for an opening rooflight to subsidise the humid environments, many rooflights.com customers purchase the Glazing Vision VisionVent Rooflight as they can achieve increased levels of ventilation effortlessly at the touch of a button. If you are planning to construct a two-storey extension with a pitched roof, you will need to install a roof window as most rooflights are designed for flat roof applications only. There are roof window options to suit every need, from electrically opening windows to conservation windows to meet stringent planning regulations. Do You Need An Architect? Prior to commencing your extension build planning, some people opt to enlist the services of an architect to help them find the best solution for their individual needs. Enlisting the services of an architect may not be needed for small scale projects but it can be beneficial for larger projects as they can adapt plans to your bespoke needs, advise on building regulations and planning permission and help you manage your budget. Appointing an architect will incur costs, so this needs to be factored into the project budget, but their advice and assistance can be invaluable especially for large scale projects.   Adding rooflights and roof windows to your extension will add an aesthetic element, allowing natural daylight to fill the space and make it more welcoming. Our experienced team are well-versed in working with customers to choose the perfect product for their chosen application, reach out to our team today and turn your idea into a reality.

We frequently get asked by customers if their builder will need to produce a FENSA certificate when installing our rooflights and roof windows, there seems to be confusion over what a FENSA is and its applications

When it comes to enhancing natural daylight and ventilation in your home, rooflights and roof windows stand out as a popular choice. They are an increasingly popular solution to a lack of natural daylight, and can elevate the aesthetics of your home. However, we understand that choosing the correct rooflight, roof lantern or roof window can be a complex task. You need to consider factors such as design, functionality and proven benefits.

Whether you’re a builder, architect or homeowner understanding lead time is crucial to a project’s success and ease

Rooflights come in all shapes and sizes, providing direct views to the sky and allowing an abundance of natural daylight to flow into any room, and the benefits of natural daylight are expansive. As opposed to vertical windows which may be obstructed by outside structures, rooflights provide uniform distribution of natural daylight throughout the day as the sun moves across the sky, providing a consistent level of natural daylight at any time of the day.A recent survey found that 84% of home buyers valued the amount of natural light in a property as the most important factor in their search, so rooflights will not only increase your mood and physical health, but they will also increase the value and appeal of your home. The Benefit Of Natural Daylight The benefits of natural daylight are plentiful, offering numerous benefits for both individuals and the environment. Increased exposure to natural daylight stimulates the production of Vitamin D in the body which is essential for bone health and immune function, contributing to a healthier life. In addition to the physical health benefits, exposure to natural daylight enhances mood therefore reducing the symptoms of depression and anxiety.Natural daylight maintains the body's circadian rhythm, commonly known as the body’s internal clock, which boosts productivity and promotes better sleeping patterns.As well as the proven physical and mental benefits for individuals, the installation of rooflights to increase the levels of natural daylight will have an impact on the environment.By maximising natural daylight in your property, you rely less on artificial sources of lighting which significantly reduces your energy consumption particularly during the summer months with longer days, in turn reducing your carbon footprint.A lesser known benefit of installing the correct rooflight is lower heating costs as sunlight can provide passive heating, reducing the need for artificial heating in the winter months. Ventilation rooflights can also provide enhanced air quality and circulation in the summer months, reducing the use of fans and artificial cooling devices. Choosing The Right Rooflight To maximise the impact of your rooflight, you should ensure that you choose the correct rooflight for your requirements. rooflights.com sells high quality rooflights to transform your home through increased natural daylight. Flat rooflights provide a contemporary aesthetic, with many flat rooflights such as the Glazing Vision Fixed Flushglaze rooflight providing ‘frameless internal views’ providing a clear view to the outside world and allowing an abundance of natural daylight to enter the home through the sleek rooflight, adding an enhanced aesthetic appeal to the property too.Roof Lanterns are an aesthetic solution, adding a touch of elegance to certain architectural projects. Their unique design features multiple glass panels which are set at angles, allowing an increased amount of daylight to enter the space, creating a light and open space.Alternatively, Dome rooflights are unique as they are often an affordable option for many projects and are commonly used in buildings such as hospitals and schools due to their versatile uses.The rooflight that you choose should depend on your specific project requirements, the architectural style of your building and your budget.The placement of your rooflight in your property will have an impact on the amount of natural daylight that enters through the rooflight.Natural daylight can help make spaces look more inviting, it can also highlight architectural features in your property adding to an elegant aesthetic appeal.If you are installing a dome rooflight, placement is important as the incorrect placement can lead to intermittent glare. If you are not sure which rooflight you require, or where to install it, get in touch with our experienced team on 01379 454020 or email us on info@rooflights.com  

rooflights.com customers frequently ask whether they need planning permission to install our rooflights and roof windows, and this depends on numerous factors