Welsh Part L consultation – Domestic new build proposals

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The Welsh New Build proposals are a bold step when seen next to the English consultation proposals for 2013.

They are however also a slow one if you consider the last improvements were October 2010 and that the next interim English change may still take effect this year. The proposed timetable for changes to the Welsh Part L (2013) approved documents gave a publication date of December 2013 and proposed implementation dates of June 2014 for non domestic and January 2015 for domestic new build. The following gives a synopsis of the consultated on proposals for Domestic New Build.

The consultation considered two main options for the CO2 emissions target for Part L

  • 25% CO2 emissions reduction
  • 40% CO2 emissions reduction. (theWelsh Government’s preferred option)

This would be an aggregate target across all house types (based on the Welsh housing mix) with some needing to do more than others depending on how comparatively easy it is to improve them.

The fabric standards are proposed to be tightened to:

Application Worst Allowed Simplified Approach
Roof 0.15 (W/m2K) 0.11 (W/m2K)
Wall 0.21 (W/m2K) 0.15 (W/m2K)
Floor 0.18 (W/m2K) 0.15 (W/m2K)
Party Wall 0.20 (W/m2K) 0.00 (W/m2K)
Windows, roof windows,
glazed roof lights, curtain walling
and pedestrian doors
1.6 (W/m2K) (whole window value) Windows 1.4 (W/m2K)
Doors 1.0 (W/m2K)
Semi glazed 1.2 (w/m2K)
Air tightness 10 m3/hr/m2 at 50Pa 6 m3/hr/m2 at 50Pa
Linear thermal transmittance 0.15 x total exposed surface area (W/k) 0.09 x total exposed surface area (W/k) (ACDs level)
PV allocation n/a Building foundation area (m2) x 0.036 kWp
(eg 50m2 ground floor area = 1.8 Peak kW of photovoltaics required)

Simplified approach

Actual compliance to be determined either by following a simplified approach using a package based on main heating fuel, or via SAP calculations to trade off elements, with the Target Emission Rate determined from the SAP 2012 notional building. Following a simplified package would automatically allow a dwelling to comply (an approach borrowed from the Scottish simplified compliance approach); but an Energy calculation (SAP) would still be required to produce the Energy Performance Certificate in any respect. If the 25% reduction instead of the 40% reduction is chosen, the simplified targets remain much the same, but the PV contribution would be reduced.

There are also a number of other key proposals within the consultation:

  • That there will be a Welsh specific variant of SAP2012 (as Scotland already enjoys).
  • The existing planning requirements for use of the Code for Sustainable Homes are proposed to be removed and they plan to take steps to simplify the application of the new standards. However, it has to be considered whether the consulted on proposals are a brave enough step considering they weren’t considering any further improvements after this (2016 targets?) from on-site requirements.
  • Future endeavours for improvements to energy performance and reduction of carbon emissions propose to focus  on the potential for off-site ‘allowable solutions’.

It will be interesting to see what makes it through to the published document come December.

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Jon Ducker is a qualified energy assessor working for Kingspan Insulation Ltd. He has an extensive knowledge of energy efficiency, renewable energy systems and sustainability in buildings with an expert knowledge of the relevant sections of buildings regulations and standards and their interactions with SAP. He provides authoritative advice regarding energy assessments for a wide range of public and private sector clients.

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