Technical update on new NHBC Standards and new Welsh Part L drafts

NHBC Technical Standards 2014

The 2014 edition of the NHBC Standards comes into effect for every NHBC registered home whose foundations are begun on or after 1 January 2014.

The Standards are the technical manual for NHBC registered builders with sections covering the design, material specification and sitework for each part of the build process. 

The new standards make no changes to chapter 6.6, stairs, or chapter 6.7, doors and windows.

Details of the changes can be found in Technical Standards Extra from October 2013.

New AD L drafts published by the Welsh Government – Due to come into force from July 2014

The Welsh Government have published drafts of new AD L guidance documents covering the thermal efficiency of new and existing buildings in Wales.

For New Build

There are five criteria to be met for a new dwelling:

Criterion 1: the calculated rate of CO2 emissions from the dwelling (the Dwelling Emission Rate, DER) must not be greater than the Target Emission Rate (TER).

Criterion 2: the performance of the building fabric must meet minimum mandatory energy efficiency standards and the fixed building services should achieve reasonable minimum energy efficiency standards.

This is intended to place limits on design flexibility to encourage the reduction of demand for space heating (and cooling) and efficient use of fuel and discourage excessive use of renewable energy solutions.

Criterion 3: the dwelling should have appropriate passive control measures to limit the effect of solar and other heat gains on indoor temperatures in summer. This is to help avoid the need for mechanical cooling and the associated energy consumption.

Criterion 4: the performance of the dwelling, as built, should be consistent with the calculated DER. There is information on site management and testing procedures that would need to be adopted to demonstrate that the performance of the building fabric and fixed building services will be consistent with the specification used for energy performance evaluation.

Criterion 5: information necessary to enable the energy efficient operation of the dwelling should be provided to the occupier in an easy to understand format.

The Target Emissions Rate (TER) is determined using SAP 2012 and the elemental specification given in Appendix R.  In this Appendix it details that windows, roof windows, glazed rooflights and glazed doors will need to achieve a notional U-value of 1.4 W/m²K or better and a g-value of 0.63. For opaque (unglazed) doors the required notional U-value is 1.0 and for semi-glazed doors the notional U-value figure required is 1.2.  This does not mean that every door or window would need to achiever this notional U-value.  Within SAP the whole building is appraised and one area may compensate for another – for example imporved floor, wall or ceiling u-values may be better than the notional value, therefore allowing relaxation of window and door U-values. 

For Existing Dwellings

For work on existing dwellings there is little change to the requirements for windows, the regulations for doors have been tightened.  Windows will be required to meet a u-value of 1.6 W/m2.K or Windows Energy Rating (WER) B and C in the case of windows or for Doors – 1.6 W/m2.K or Doorset Energy Ratings (DSER) E.

For existing dwellings there will be a requirement for consequential improvements. These are summarised in a ministerial statement by Carl Sargeant, Minister for Housing and Regeneration who notes that Part L will require all homeowners undertaking extensions or improvements such as a loft or garage conversion to upgrade walls, roofs and floors (windows will not be affected) to meet new fabric standards.   He also goes on to confirm that conservatories should not be heated or cooled if they are to be considered exempt from the Building Regulations. If a conservatory is heated or cooled then the relevant fabric and fixed building services requirements will apply.

If you have any comments on these drafts or wish to discuss their implication, please call the BWF Helpline on 0844 209 2610