DOORS , WINDOWS & FITTINGS
' CHALLENGES WITH DOCUMENT L '
by Wojciech Brozyna - MD of Aluprof UK
Net Zero Carbon Homes by 2050 , a step too far ? Well it certainly is a challenge for the Construction Industry and home improvement , but it is possible to achieve ? Let ' s first look at some of today ’ s facts : 27 % of our carbon emissions in the UK comes from heating our buildings , with 18 % coming from our domestic building stock . 80 % of our homes that will be needed in 2050 have already been built and we are still building homes today that are not in line with net zero . So what do we have to do ?
Currently our homes range from 90 to 170 kWh / m2 energy usage per year , in 2050 we need to have our homes between 40 to 60 kWh / m2 per year . We will achieve this by taking a whole building approach , increasing thermal insulation whilst reducing air permeability and cold bridging . Obviously we will need to stop using fossil fuels such as gas as soon as practicable and move to heat pumps as the most accessible technology at the moment . Currently over 85 % of homes in the UK have gas boilers . A gradual phase out of gas boilers and an increase in heat pump installations will allow the gradual increases required in the electricity grid , which continues to be decarbonised to use more renewable energy .
To achieve our net zero target , our well insulated homes will require less zero carbon energy to run and it is only then when we can claim a ‘ Net Zero Carbon ’ balance for our building stock .
As for windows and doors , it is anticipated that these should achieve 0.8 W / m2 . K by 2025 . Couple these lower values with increased insulation in walls , roof and floor and we will see space heating demand decrease to 25 to 50 kWh / m2 / yr . Whilst it is challenging to increase insulation in the building fabric , either internally or externally , one issue that our industry must tackle is that of cold bridging , especially around the installed windows and doors . With a high performance window or door frame typically 70mm in width , how do we ensure that the structure supporting the window increases in insulation from the frame U value to the full thickness of the wall which will typically be 0.15 W / m2 . K without dipping and creating a cold bridge ? Currently many replacement window installations ignore the need to continue the thermal insulation within the window to link into the surrounding structures insulation . Ignoring these thermal requirements around the window reveal can heavily reduce the purported gains of installing a high performance window or door .
Basically no one element of the building structure can be looked at in isolation . High insulation building fabric goes hand in hand with high performance windows and doors , with the caveat of careful detailing around window and door openings . The ‘ fabric first ’ approach is key to achieving our net zero target , indeed , just opting for home insulation now will heavily reduce current carbon emissions by using less fossil fuels . Adding to a well insulated and airtight home , the
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