After insulation, airtightness is the most important factor determining the energy efficiency of a building. It’s estimated that 40% of heating energy loss comes from windows or the gaps around windows. With large glazing panels and bi-folding doors more popular than ever, make sure that you specify the right doors and windows for your plot.
When looking to buy windows it’s worth knowing that there are up to five levels of wind load resistance – from one to five – and three deflection classes – A to C. These measure a window or door’s structural strength. The higher the number, the better the performance.
The BFRC’s window rating system was introduced to meet the need for simple and accurate certification regarding the thermal performance of window products. Each window rated by the BFRC has a unique label identifying its energy efficiency. Windows are rated on an A to G scale based on their total energy efficiency, which allows home-builders to quickly and easily choose the most suitable window for their needs.
As well as considering the outside climate, the levels of sunlight that enters a home need to be investigated before a new home design is finalised. North-facing rooms get less sun than any other, and windows with a high Energy Rating will maximise what energy is gained from the sun so it can remain warm throughout the year.
Hugh Moss, Head of glazing specialist Reynaers at Home, comments:w “In our architects’ survey 57% of British architects said the most popular industry trend today in residential housing was energy efficiency. When asked what most homes were missing, some 13% responded with the issue of sustainability.
“Energy used in constructing, occupying and operating buildings represents approximately 50% of greenhouse gas emissions in the UK. In the move towards sustainability, construction and buildings in general have been highlighted as a major area for attention. Innovation and sustainable product design is key in reducing the amount of energy used both in the construction of buildings and in their everyday use.”
Of course, glazing is not the only factor determining a structure’s airtightness. Ventilation systems that filter the air in and out of a home are also at risk of allowing heat to leak. However, including a mechanical ventilation heat recovery (MVHR) system creates a controlled and efficient living environment without the need to open a window.
Make sure that all your tradesmen are thoroughly briefed on your airtightness strategy prior to the build. It only takes one weak element to allow all your careful preparations to go to waste.