How to Avoid an Extension That’s Too Hot and Too Bright
Hankering after a light-filled glazed extension? Ensure you swerve the pitfalls that could make it uncomfortable to use
Kate Burt
10 July 2022
Houzz UK. I'm a journalist and editor, previously for the Independent, Guardian and various magazines. I'm now excited to part of the editorial team at Houzz UK & Ireland, bringing the best of British and Irish design, interiors and architecture to Houzz.com.
Houzz UK. I'm a journalist and editor, previously for the Independent, Guardian and... More
Contemporary extensions often feature a lot of glass – lovely to look at but a potential headache-inducing sweatbox over the summer months if not well-designed. Here, three architects talk about why some extensions can wind up being too hot, or too glaringly bright, for comfort and explain how to ensure your design doesn’t suffer from any of these problems. They also give tips for retrospectively tackling them if your extension has already been built.
Professional advice from: Sam Cooper of E2 Architecture + Interiors; Daniel Rees of Rees Architects; Ruth Campbell of Campbell Cadey
This article is from our Most Popular stories file
Professional advice from: Sam Cooper of E2 Architecture + Interiors; Daniel Rees of Rees Architects; Ruth Campbell of Campbell Cadey
This article is from our Most Popular stories file
Understand the issues
“We come across this a lot,” Sam Cooper says. “People often ask for designs that will create too much heat and brightness. The causes include too much glass, especially in the roof, and no thought about providing shading.”
“A lot of people want that inside/outside space – basically, a big wall of glass,” Daniel Rees agrees. “We’ve actually taken a lot of these out. It might look great in a picture, but is it useable?
“To solve the problem,” he says, “we need to think about the orientation of the building and how much sun there is in relation to how much glass. A south-facing extension risks being hot all day. If it’s west-facing, it’ll get the sun in the evening; if it’s east-facing, it’ll get the sun in the morning.
“It’s also about visual comfort,” he continues. “If you’re walking from the darker middle of the house into an extremely bright extension, you could get sun-blinded.”
“We come across this a lot,” Sam Cooper says. “People often ask for designs that will create too much heat and brightness. The causes include too much glass, especially in the roof, and no thought about providing shading.”
“A lot of people want that inside/outside space – basically, a big wall of glass,” Daniel Rees agrees. “We’ve actually taken a lot of these out. It might look great in a picture, but is it useable?
“To solve the problem,” he says, “we need to think about the orientation of the building and how much sun there is in relation to how much glass. A south-facing extension risks being hot all day. If it’s west-facing, it’ll get the sun in the evening; if it’s east-facing, it’ll get the sun in the morning.
“It’s also about visual comfort,” he continues. “If you’re walking from the darker middle of the house into an extremely bright extension, you could get sun-blinded.”
Split up your views
“I think people automatically assume lots of glass is what they want,” Sam says. “We like to reduce the amount and frame views into the garden instead.”
Daniel agrees and references one of his projects, pictured here. “It could have been easy to do a big, square extension, but instead we created three levels where the windows and doors connect with the space.”
There’s a window seat that frames a view of the garden on the left, a big opening in the centre for views from the dining table, and a window in the kitchen area.
“We like to relate the glass to the internal zones,” Sam says. “We’ll ask questions such as, ‘Where will you put the TV so it doesn’t get glare on it?’ Splitting the glass up also gives you opportunities to put furniture against the garden wall, or tuck in a window seat, or hang a picture. Wall-to-wall glazing can be restrictive.”
Browse the Houzz Professionals Directory to find local architects.
“I think people automatically assume lots of glass is what they want,” Sam says. “We like to reduce the amount and frame views into the garden instead.”
Daniel agrees and references one of his projects, pictured here. “It could have been easy to do a big, square extension, but instead we created three levels where the windows and doors connect with the space.”
There’s a window seat that frames a view of the garden on the left, a big opening in the centre for views from the dining table, and a window in the kitchen area.
“We like to relate the glass to the internal zones,” Sam says. “We’ll ask questions such as, ‘Where will you put the TV so it doesn’t get glare on it?’ Splitting the glass up also gives you opportunities to put furniture against the garden wall, or tuck in a window seat, or hang a picture. Wall-to-wall glazing can be restrictive.”
Browse the Houzz Professionals Directory to find local architects.
Add a overhang
“When the glass is set back, you get a reveal, meaning it shades the glass slightly,” Daniel says. This, known as ‘passive shading’, could come in various forms, including projecting eaves or an overhang above the window, like the one seen here.
This sort of design will be especially helpful in the summer if the glass is south-facing. “The sun will be too high in the sky to shine directly into the room,” Daniel explains, “but in the winter, when the sun is lower, you’ll still get the benefits of it warming up your space.”
Tour this extension to find out more.
“When the glass is set back, you get a reveal, meaning it shades the glass slightly,” Daniel says. This, known as ‘passive shading’, could come in various forms, including projecting eaves or an overhang above the window, like the one seen here.
This sort of design will be especially helpful in the summer if the glass is south-facing. “The sun will be too high in the sky to shine directly into the room,” Daniel explains, “but in the winter, when the sun is lower, you’ll still get the benefits of it warming up your space.”
Tour this extension to find out more.
Bring in a brise-soleil
This suggestion of Sam’s is a structure you may have seen, especially on very modern buildings. As you can see, a brise-soleil consists of a section of slats projecting out at roof height and bringing dappled shade to the interior of the space.
This suggestion of Sam’s is a structure you may have seen, especially on very modern buildings. As you can see, a brise-soleil consists of a section of slats projecting out at roof height and bringing dappled shade to the interior of the space.
Construct a canopy
An alternative is to build a canopy outside if you have the space. “It doesn’t have to be huge,” Ruth Campbell says, “just half a metre will create enough shadow.”
An alternative is to build a canopy outside if you have the space. “It doesn’t have to be huge,” Ruth Campbell says, “just half a metre will create enough shadow.”
Include a window seat
This design feature not only brings daily pleasure, it can also provide the same benefits as an overhang outside. “A couple of our projects have window seats,” Daniel says. “They’re quite deep, so you get views, but not direct, bright sunlight.”
This design feature not only brings daily pleasure, it can also provide the same benefits as an overhang outside. “A couple of our projects have window seats,” Daniel says. “They’re quite deep, so you get views, but not direct, bright sunlight.”
Install blinds
Active shading includes fittings such as blinds, which can potentially be added more easily retrospectively. “Go for electric blinds,” Sam advises, adding that translucent blinds might be enough to do the job. “Sheer blinds will diffuse the light, not block it.”
“Make them integral blinds,” Ruth says. “If you design in small recesses above the doors and windows for them to sit inside, the blinds won’t ruin the lines.” She recently completed a project where she added such recesses, but not blinds, giving the homeowners the opportunity to install them only if, after using the space for a while, they felt they really needed them.
Active shading includes fittings such as blinds, which can potentially be added more easily retrospectively. “Go for electric blinds,” Sam advises, adding that translucent blinds might be enough to do the job. “Sheer blinds will diffuse the light, not block it.”
“Make them integral blinds,” Ruth says. “If you design in small recesses above the doors and windows for them to sit inside, the blinds won’t ruin the lines.” She recently completed a project where she added such recesses, but not blinds, giving the homeowners the opportunity to install them only if, after using the space for a while, they felt they really needed them.
Try a tree
“Install an additional landscaping treatment to provide some shelter and shade,” Ruth suggests.
“East- and west-facing rooms are harder to passively shade,” Sam says. “In the summer, the sun rises very early and, in east-facing rooms, it’ll be beating right in until around midday – meaning a full six or seven hours of it. With west-facing spaces, you’ll get the same, but in the afternoon. In this instance, a deciduous tree can be a good idea if possible.”
“Install an additional landscaping treatment to provide some shelter and shade,” Ruth suggests.
“East- and west-facing rooms are harder to passively shade,” Sam says. “In the summer, the sun rises very early and, in east-facing rooms, it’ll be beating right in until around midday – meaning a full six or seven hours of it. With west-facing spaces, you’ll get the same, but in the afternoon. In this instance, a deciduous tree can be a good idea if possible.”
Consider a clerestory window
This is another idea you might be able to use retrospectively with the help of a design professional. “We’ve previously suggested a client take out some really big roof lanterns and build a flat roof with a clerestory window instead,” Sam says.
A clerestory is a slim window positioned high up, like the one pictured here. “It’s vertical rather than horizontal glass, so you get much less heat gain [than with roof lanterns], which is more comfortable,” Sam says. “You do still get the light, though – it’ll just be a more diffuse.
“Uncontrolled light is really uncomfortable,” he adds. “It reflects off walls and surfaces and is visually uncomfortable – it makes you tired. A diffuse light is much softer and more relaxing.”
This is another idea you might be able to use retrospectively with the help of a design professional. “We’ve previously suggested a client take out some really big roof lanterns and build a flat roof with a clerestory window instead,” Sam says.
A clerestory is a slim window positioned high up, like the one pictured here. “It’s vertical rather than horizontal glass, so you get much less heat gain [than with roof lanterns], which is more comfortable,” Sam says. “You do still get the light, though – it’ll just be a more diffuse.
“Uncontrolled light is really uncomfortable,” he adds. “It reflects off walls and surfaces and is visually uncomfortable – it makes you tired. A diffuse light is much softer and more relaxing.”
Seek out specialist glazing…
“You can get solar control glass [which has a special coating to reduce solar gain],” Sam says. “We’d recommend it for large areas of east or west-facing glazing. It does mean in the winter you don’t benefit from the heat gain when you want it, though. Also, the glass has a tint to it, which is a consideration. So if it’s an option to shade passively, that’s always our first choice.”
“There are solar protection finishes that increase thermal performance, too,” Ruth says. “We used a high-performance solar control glass in our Library House project [pictured here], where you can see the glass is slightly darker.”
“You can get solar control glass [which has a special coating to reduce solar gain],” Sam says. “We’d recommend it for large areas of east or west-facing glazing. It does mean in the winter you don’t benefit from the heat gain when you want it, though. Also, the glass has a tint to it, which is a consideration. So if it’s an option to shade passively, that’s always our first choice.”
“There are solar protection finishes that increase thermal performance, too,” Ruth says. “We used a high-performance solar control glass in our Library House project [pictured here], where you can see the glass is slightly darker.”
…or treat your glass externally
Ruth also suggests a similar idea that uses different technology and can be used retrospectively, making it a far more viable option if you’ve inherited a hot, glass-heavy extension.
“I went to see Space Group Architects’ Binary House [pictured] over Open House London weekend,” Ruth says, “and the back of the house had glass with these sort of slim metal blades on it, which significantly cut down the amount of sun coming in.”
The product Ruth saw, seen here, is called MicroLouvre. It’s a brass mesh made up from tiny louvres, or blades, designed to control solar gain. At Binary House it was, in fact, laminated into the glazing. However, the dense mesh sheets typically come in an aluminium frame as a screen product and these can be fixed externally to existing windows or glazing.
Ruth also suggests a similar idea that uses different technology and can be used retrospectively, making it a far more viable option if you’ve inherited a hot, glass-heavy extension.
“I went to see Space Group Architects’ Binary House [pictured] over Open House London weekend,” Ruth says, “and the back of the house had glass with these sort of slim metal blades on it, which significantly cut down the amount of sun coming in.”
The product Ruth saw, seen here, is called MicroLouvre. It’s a brass mesh made up from tiny louvres, or blades, designed to control solar gain. At Binary House it was, in fact, laminated into the glazing. However, the dense mesh sheets typically come in an aluminium frame as a screen product and these can be fixed externally to existing windows or glazing.
Boost your (air) circulation
Ventilation is an important factor in keeping spaces cool. “Having lots of opening areas that provide natural ventilation is key,” Ruth says, “particularly, if possible, on opposite sides of the room. Openable roof lights will also let the hot air escape.”
Ensure you’re able to reach to open high windows, or have a mechanism installed that allows control from lower down the wall.
“Also consider a passive ventilation system,” Sam adds. This is a system that regulates the internal air temperature and brings fresh air in while sending stale air out. “You want to have some sort of secure ventilation that allows you to shut the doors or lock them at night, but keeps the air moving,” he says.
Tell us…
Do you have experience of a too hot or too bright extension? What did you do to make it more comfortable? Share your tips in the Comments.
Ventilation is an important factor in keeping spaces cool. “Having lots of opening areas that provide natural ventilation is key,” Ruth says, “particularly, if possible, on opposite sides of the room. Openable roof lights will also let the hot air escape.”
Ensure you’re able to reach to open high windows, or have a mechanism installed that allows control from lower down the wall.
“Also consider a passive ventilation system,” Sam adds. This is a system that regulates the internal air temperature and brings fresh air in while sending stale air out. “You want to have some sort of secure ventilation that allows you to shut the doors or lock them at night, but keeps the air moving,” he says.
Tell us…
Do you have experience of a too hot or too bright extension? What did you do to make it more comfortable? Share your tips in the Comments.
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The end of our east facing extension is entirely glass. Internal blinds are a must in the summer. The roof light was still unbearable until we had a UV window film installed. The film made a huge difference in reduced heat and glare without blocking the view of the sky, however the view at night has changed. Instead of stars we now see ourselves relected as in a mirror. It was still worth it.
I’m considering external shutters for our east facing study windows, brise soleil over the south facing bathroom windows and an awning or shade sail over the patio outside the east facing French windows.
Our kitchen dining extension is south facing. We live in Shropshire. Sun comes from the left and goes around to the right. Sun is out of the way by tea time as far as extension is concerned. We have a large flat sky light and five bifold doors. I absolutely love my space. It only gets air if I open the door/s or utility door or study next to it. I have never been too hot, even in times of extreme heat ie the dry hot summer we have just had here. I worry more about the grass lol! I love my doors being folded back. I have made a garden through blood sweat n tears from nothing. Our first real home after 19 military quarter homes! Thought maybe I was wrong not to have a long thin window on one side, but wanted to have a sofa in the room etc and it would have looked daft behind it. Also the view isn't the best, can't help that at the moment though. Will soon be sorted out! What can I say! One happy customer. The view is uninterrupted from window frames. just thin ones etc. It's cool to cook in the evenings or day times too. hope this helps you to decide on a choice. If I'd have read this, I probably wouldn't have gone for it, but how wrong that would have been hey!