Saving daylight: how to make sure your extension or loft conversion gets enough sunlight

You’re adding space but have you made sure you won’t be losing light? Find out how to plan natural light into your extension or loft conversion project

Velux kitchen extension with three rooflights
(Image credit: Velux)

An extension or loft conversion can add much needed space to your home. When you extend – be it a loft bedroom, or a spacious new kitchen – you may spend a lot of time thinking about your new finishes, flooring and paint colours. But have you thought about how much natural light your new space will get?

If the answer is no, you’re not alone. To many homeowners, daylight and glazing is an afterthought. When you add an extension for example, you may be doubling your floor area and the back of the original space ends up being starved of daylight. To avoid this, you will need to plan glazing in from the start. Luckily, this can be easily done with some top tips and handy tools. We have teamed up with VELUX – experts in roof glazing – to help you get your project off to a bright start.

1. Use the VELUX Daylight Calculator

Before you worry about having to work out how many windows your space needs manually, have a look at VELUX’s Daylight Calculator. All you need to do is input the dimensions of your room, and the extension (or the dimensions of your new loft room) and the clever calculator will advise how many rooflights you will need. It also recommends the right products, then allows you to input your details to speak to an expert. This is a great way to get an idea of how much of your roof will require glazing, before you even start to plan things like the kitchen design or bedroom layout.

2. Know the simple formula to calculate glazing

Whether you use the calculator or not, it helps to know that the glazing area needs to be equal to 15–20 per cent of the floor area of your new room. This should give you a good picture of not necessarily how many windows you need, but how many square metres of glazing that is. If the space already has windows or glazed doors, you can deduct these and make the rest up with rooflights.

Before: scroll to see how much light was increased thanks to an extra rooflight

Image 1 of 2

loft conversion with only one window

One rooflight is not enough for a space of this size
(Image credit: Velux)

Before: scroll to see how much light was increased thanks to an extra rooflight

Image 1 of 2

loft conversion with only one window

One rooflight is not enough for a space of this size
(Image credit: Velux)

3. Know which direction your house faces

Do you know which way your home faces? It sounds simple, but knowing whether your home is oriented northwest, southeast – or anywhere in between – is important for working out when the sun will hit your extension. A north facing extension will need as much glazing as you can manage as it is not oriented to get the full sun for many hours. Windows on the side elevations will help increase daylight, but the great thing about roof glazing is that with the sun overhead, light is not impeded as easily and you can bring it in for much of the day.

4. Plan your space around the light

Another reason home extenders get tripped up is because they decide on the layout before working out how light their space will be. You can bring lots of light to the outer edges of your room, but interior corners may end up being darker than you thought. Planning glazing from the start will help, but also being open to redesigning the space around daylight is another route to success. In the case of a kitchen diner, the kitchen and dining area will want plenty of light for tasks and entertaining, but a cosy sitting room could be placed to the back of the space. That way, you get the light right where you need it.

Before: scroll to see how adding rooflights improved the space

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Velux kitchen extension before enough rooflights were installed

Though the kitchen is well lit, the dining space and interior of the room need more light
(Image credit: Velux)

Before: scroll to see how adding rooflights improved the space

Image 1 of 2

Velux kitchen extension before enough rooflights were installed

Though the kitchen is well lit, the dining space and interior of the room need more light
(Image credit: Velux)

5. It’s not only about light

Of course windows are not just for light – they help ventilate a space, too. This will prevent it from becoming too hot on sunny days or too stuffy when everyone has been holed up inside for the weekend. Rooflights are a great way to release warm stale air, as hot air rises. Glazing on other elevations will help create a good flow of air through the space. Again, consider glazing from the start and you will find it much easier to create a bright, light and airy extension.

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