Rooflight Sizes: Getting the Perfect Sized Window

When you’re building a new house, or constructing an attic conversion, getting the right size roof window makes a big difference to the feel of the final room. Roof windows, or rooflights, are a fantastic way to maximise natural light and add ventilation to attic rooms (or to other roofed rooms of a house).

Dakea’s roof window configurator tool will help you to get the perfect window for your project – including size, material and other specifics. Be sure to also read our tips below for more information on choosing the right rooflight size.


Configurator Tool

Standard Dakea Roof Window Sizes

Our rooflight sizes range from small windows, C2A (55x78cm), to large, U8A (134x140cm). The dimensions refer to the entire window including the frame.

The system for rooflight sizes is a combination of letters and numbers. The first letter indicates the frame width and the number indicates the frame drop (or length).


Not all our roof windows are available in all sizes. Use our window configurator tool to find out which size and product best suits your needs.

How big should my rooflight be?

A lot of this will come down to personal preference, as well as budget. The larger the roof window, the more light (and heat) it will let in. However, even a reasonably small rooflight can let in a lot of sunlight depending on the size of the room and the position of the window.

The best option is to use our window configuration tool to help you pick out the best choice for you.

Size Considerations

There are a few factors that should affect your decision in choosing a rooflight size for a project:

Type of Room


The type of room you’re constructing will impact what size roof window will best suit it. Kitchens and bathrooms are areas in a home prone to condensation build up due to activities such as cooking and showering. Choosing a larger window helps to reduce the build up of condensation as it provides better ventilation.


Why not read our tips for builders and installers on stopping window condensation?


The type of room also impacts window size from a usage perspective. Bathrooms, for example, are used much less frequently than other rooms in the home, so having a particularly large window in the bathroom might be less of a priority than the same in a living room, for example.

Bathroom with large rooflights

Project Budget


While creativity and inspiration might call for beautiful large windows, every project has a budget to keep in mind. Whether it’s your own company's budgets for a new housing complex, or a client’s personal budget, it’s important to consider how cost will have an impact. Larger windows do cost more than smaller windows - although often one large window is more cost effective than two smaller.


Dakea specialise in manufacturing high quality, affordable windows for professionals. This means that in our range you’ll always be able to find the perfect roof window for your budget without compromising on quality.

Single large sized roof window

Shape & Size of the Room


On the whole, the larger the room, the larger the roof window that’s needed to maximise light and create a welcoming space.


However, there are some exceptions. Where rooms are particularly large or have interesting shapes, like L-shapes, you might find multiple smaller windows are the most effective way to create a comfortable environment with plenty of light.


As a rough guide, for 25m2 of space, 5m2 of window is needed to maximise the light. The more this is reduced, the darker the room will feel. Of course, going beyond this will only improve the visual effect of the room and the expanse of view from the windows.


Bear in mind that with this much light, you might want to check out our blinds for roof windows too!

Multiple smaller rooflights

How much light is needed?


South-facing rooms are likely to receive sunlight throughout the day. On the other end of the spectrum, north-facing rooms might see little direct sunlight. This means you can use smaller rooflights in south-facing rooms while north-facing rooms might require bigger windows to achieve the same light feel.


Considering how much light a room will receive, according to the direction it faces, will help you to choose the best rooflight size. If you’re converting an attic that has both north and south facing walls, you could reduce the cost of the build by choosing to place multiple smaller windows in the south wall, for example, rather than in the north. You’ll get a much lighter room for the same budget.


It’s worth remembering, however, that south-facing rooms that get sun all day might get too hot if the windows are large. You could opt instead for a couple of small rooflights on the south-side and a larger window on the north-side to help balance light and temperature.

South facing roof window

Views & Privacy


Even with roof windows, you should consider how they impact views from inside as well as the privacy of residents. In bigger builds, such as new housing complexes, this might be harder to predict, but in attic conversions on existing properties, it should be relatively easy to plan.


Roof windows are a great way to maximise light and privacy, but there are still possibilities of windows being in view of opposite houses, for example. Consider what the room will be used for and how this affects the required privacy levels.


Bathrooms, for example, that can be seen from opposite houses even through roof windows, might want smaller windows than a similar set up for a kitchen or living room, for example. We do have a range of opaque roof windows to increase privacy while maintaining light.


On the other hand, if a house has fantastic views, you might consider choosing large windows to increase the view from inside. This will increase the value of the property.

Small size roof window

Skylight Sizes

Skylight sizing is different to rooflight sizing due to their function. While roof windows are used in attic conversions, skylights are used in unoccupied spaces. They help to add ventilation and light to lofts that are used for storage, for example.

This means that you may not need the same size skylight for a loft as you would need roof window for a converted attic.

It’s often a better idea to choose either one small skylight or multiple small skylights, but this does depend on the size of the room. A bigger loft space might need multiple skylights or a larger skylight to ensure it’s well lit and ventilated.

What are the standard skylight sizes?

Skylight type Size code Size (cm) Price (without VAT)
KFE 4555 45×55 £135
KFE 4573 45×73 £150.50
KFE 6565 65×65 £187.50
KFE 8585 85×85 £248
KFE Red 4555 45×55 £135
KFE Red 4573 45×73 £150.50
KFE U 4573 45×73 £155.50


Roof windows come in a wider variety of sizes, as you can see above. The key difference is that skylights are designed for use in cold rooms, such as garages or storage lofts, while roof windows are designed for use in warm rooms such as converted attics.

Get the right size roof window

Configurator Tool

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