What Needs To Be Considered For The Changes To Part L 2013?

BWF members such as yourselves frequently use our Member and Technical Helplines for assistance on a wide range of Employment, Health and Safety, Pay and Technical issues. We’re putting up a frequently asked question every Tuesday in order to help members and illustrate the type of advice we are able to provide. If you have any questions that you would like to see featured, we would be happy to assist. This question and many others like it can be found in our Question Centre. If you want further advice on any of the issues, don’t hesitate to ring the helpline or browse our extensive publications library, which includes our advice on resin exudation in joinery timber, care of products on site, and guidance on the new Parts L and F of the building regulations. This week: What Needs To Be Considered For The Changes To Part L 2013? The consultation process for the 2013 changes to Part L of the Building Regulations has begun. We need input from members to determine how best to proceed to make manageable and cost effective proposals. We know that the changes in April 2013 will be a step towards the 2016 requirement for zero carbon homes. These have been defined by the Zero Carbon Hub as having ‘as built’ emissions of: – 10 kg CO2(eq) /m2/year for detached houses
– 11 kg CO2(eq) /m2/year for other houses
– 14 kg CO2(eq) /m2/year for low rise apartment blocks One argument could be to propose better enforcement. We hear that many window manufacturers are still not meeting their obligation to demonstrate the thermal performance of their windows and external doorsets and may not be achieving the necessary levels. This is seen as a competitive advantage as poorer thermal performance can mean lower costs but a customer would be accepting work which did not comply with the Building Regulations and a manufacturer would be supplying a product which was not fit for purpose. Better enforcement of the Building Regulations could catch those products which do not perform to the requirements leading to a general improvement overall. If the levels of thermal performance are to be improved, how much should this be? The levels introduced by the 2010 amendments for replacement windows changed the recommendations as shown below: Requirements for replacement windows:

For a U-value of 1.6 W/m2K windows generally require an argon filled, 24mm glass unit with a low-e coating of 0.05 and a warm edge spacer bar, giving a centre pane U-value of 1.2 W/m2K. To achieve a 10 % improvement in whole window U-value from 1.6 W/m2K to 1.4 W/m2K the glass unit would need to be changed to have a centre pane U-value of 1.0 W/m2K which could be achieved by changing to a low-e coating of 0.01 or by moving to an argon filled triple glazing unit. If the Energy Rating of the window was to be improved from a band C to a band A which requires an improvement in energy performance from an Energy Index  of  -11 at the top of band C to 0 at the bottom of band A. We can see on the BFRC website the range of U-values and solar factors which can provide these ratings for timber casement windows. Requirements for Energy Rating bands A and C:

It can be seen that by using glass units with a good solar transmittance and controlling the frame factor, the ratio of timber to glass in the window, good energy ratings can be achieved with poorer U-values and this may result in a less costly route to compliance when compared to the U-value route. Please send your views on these changes to Kevin Underwood via email at visit the Members’ Day Pages.