56 BUILDING FABRIC


and delivers a build that is closer to the expected energy performance. However, while a product may say it meets Part L or has a certain U-value, this may not be the case once it is installed. Therefore, it is vital that housebuilders specify products that help mitigate the gap between performance on paper, and actual erforance of a fi nished build A patented Integrated Expanding Thermal Collar has been developed to ensure the thermal integrity of the window and roof is as designed, thus removing the reliance on an additional collar and helping achieve Part L requirements. It also improves airtightness and psi-values for SAP, further helping housebuilders.


In another move towards the Future Homes Standard, last year’s update to Approved Document F relates to improving ventilation in homes. With a drive towards ore enery effi ciency, homes are now designed to be insulated and as airtight as possible to reduce draughts and avoid heat loss. The result of this is an increase in the retention of moisture in the home with a lack of air circulation and a need to maintain healthy air quality. To balance any lack of natural ventilation, mechanical ventilation and/or background ventilation are made requirements for new homes under the updated Building Regulations. Now, when housebuilders specify new windows in their new developments, trickle vents ust be installed, or suffi cient background ventilation must be provided by other means. Once again, Part F requirements for background ventilation are supported thanks to innovations such as a window top handle which allows for controlled trickle ventilation when the window is fully closed and securely locked. The National House Building Council (NHBC) will not accept other window types that provide background ventilation by being latched in the partially opened position. This year also saw an update to ‘Overheating: Approved Document , secifi cally ararahs  to  ‘Protection of Falling,’ which states that openings which are intended to be open for long periods to reduce overheating risk might pose a higher risk of falls from height.


Again, some window manufacturers have taken the initiative, design product features that help support housebuilders who urently need to fi nd answers to meet this latest update to Building Regulations.


Colin Wells is head of technical at Keylite Roof Windows


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