Lee Griffiths, Technical Sales Manager at Dakea GB, explains what to consider when choosing a roof window to ensure a ease of installation; and to get the most from it in terms of light, energy efficiency and user experience.
Checking for integrity
Before deciding on a particular size of window, the rafters and structural integrity of the roof should be examined. Most roofs can be adapted to take roof windows, however cutting structural rafters and joists can weaken the roof. Ensure this has all been taken into consideration before the project begins and if in doubt always seek further advice.
More windows can be better than one
While of course bigger windows admit more daylight per window, it is worth considering a number of smaller windows instead. For example, rather than one large window on one side of the room, four smaller roof windows of the same total size that are evenly distributed on either side of the room can allow much more light in, making better use of the space available.
Nailing the pitch
There is no single one-size-fits all window size or placement – the roof window should always be placed at the correct height, and be of the right size for the convenience and functionality of the end user. This will of course vary depending on the features of the roof, such as the pitch.
If you are installing a roof window into a property with a low pitch roof, you will need a larger roof window to achieve the same amount of light as in a house with a steeper roof pitch.
In addition to the size of the roof window you should also consider the height at which the window is installed. It is important the occupants have a clear view when looking out the window, so the general rule of thumb with sizing is that the lower the pitch of the roof, the higher the roof window should be placed.
Lining up the shot
More light can also be introduced into the room by correctly designing the interior lining – the wall area directly around the window. If the lining is cut straight in line with the window frame, this limits the path of light. However, by creating a vertical line below and a horizontal line above the window, more light can enter the room.
Ensuring that the lining is correctly splayed will also improve the heating efficiency by allowing warm air to circulate freely around the room. Incorrectly splayed lining causes warm air to be trapped, and may cause condensation.
A positive outlook
As well as considering the interior of the home, the visual impact of the roof windows will have on the outside of the property needs to be examined. The placement of the roof windows should be considered in relation to existing windows in the house, and then balance these with the need for internal light in the space. By doing this, roof windows will fit in with the rest of the rest of the home, whilst performing according to the homeowners needs.
Energy efficiency: the hot topic
When considering the specification and installation of the window, it’s important to remember to create a tight seal around the window and repair the roofing membrane properly after installation. Filling the un-insulated gap between the rafters and the roof window caused by installation will not only ensure it is compliant with Part L1B of the Building Regulations, but this also means water and air cannot pass through. Exposed gaps can cause interior surface damage and colder room temperatures, compromising energy efficiency and a resulting rise in heating costs.
Leading manufacturers will be able to provide innovative installation accessories, such as the Dakea IFC Insulating Foam Collar – a rebated foam profile manufactured to fit the window frame. It offers superior insulation and reduces the installation time taken normally to fill the gap to approximately three minutes per window.
In addition, the window itself can contribute to energy efficiency. A double-pane window glazing unit filled with a highly insulating gas such as krypton will prevent thermal bridging to the outside. It is also wise to select a window with a coating on the glass that will reflect the heat back into room. This will contribute to better energy efficiencies and keep bills low for the homeowner.
For loft conversions and renovations, roof windows provide an excellent way to provide light and ventilation to the new space. When planning the installation ensure you’ve considered all the crucial factors to provide a solution that meets the needs of the homeowner and creates an aesthetically pleasing finish, both inside and out.
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