With the 2013 technical guidance document Approved Document L1A (Conservation of fuel and power in new dwellings) now in place, there is a great deal of variability that can be adopted to achieve compliance. As such, Knauf Insulation recommends adopting a prudent commercial solution without compromising on quality.
Stephen Smith Market Development Manager at Knauf Insulation Northern Europe comments: Some of the U-values in the elemental recipe in Approved Document L1A may not be beneficial to all housebuilders and developers, in terms of the practical and commercial elements.
As an example, consider a cavity wall U-value within the notional dwelling at 0.18W/m²K. This requires a wall thickness between 365mm and 380mm. To achieve compliance with 2010 Regulations, the majority of volume housebuilders are constructing cavity walls to a U-value of 0.25W/m²K. It is possible to exercise the design flexibility which has been included within ADL1A 2013 and adopting a more practical approach. Improving on other elements such as pitched roofs insulated at ceiling level (Knauf Insulation would recommend a U-value of 0.11W/m2K rather than 0.13W/m2K), it is possible to maintain the cavity wall U-value of 0.25W/m²K with an overall wall thickness of just 300mm.
Knauf Insulation can demonstrate how compliance can be achieved with all house types with a practical, yet sensible fabric approach to make sure that what it recommends is best suited to the developers needs and not just a compliance exercise.
The revisions also include new compliance criteria, Target Fabric Energy Efficiency (TFEE) that recognises the importance of a Fabric First approach to meeting the ultimate ambition: Zero Carbon Homes. This is calculated using actual dwelling dimensions and the performance values in the current notional dwelling specification. For the 2013 revisions this value is increased by 15 per cent, allowing builders to make a smaller interim step as they prepare for Zero Carbon Homes.