Building Regulations 2013 – consultation on energy efficiency – consequential improvements

Existing Homes

The most crucial proposed change for existing dwellings is that of consequential improvements. Similar requirements are already in building regulations but only apply to homes over 1,000m2 of floor space. The new regulations propose consequential improvements for all dwellings, regardless of size.

There are two aspects to consequential energy efficiency improvements. Firstly, what triggers when they have to be carried out and secondly what improvements have to be carried out.

The triggers are when floor space is increased for example with a new extension or a loft conversion. Another trigger is when a certain amount of windows are replaced. The consultation seeks views on whether this should be when 50% of an elevations windows are replaced or when 50% of all windows are replaced, or even some other trigger level.

The next issue is what needs to be done. Currently energy efficiency improvements up to the value of 10% of the principle works are required, where it is “technically, functionally and economically feasible”. However, with the advent of Green Deal there is an argument that any Green Deal works require no upfront costs and therefore will be below the 10% threshold. If the occupier does not want to pursue Green Deal then they must look at the interventions listed in a valid EPC certificate for the property or consult the options listed in the guidance.

Typically for extensions it is expected that interventions such as loft or cavity wall insulation, hot water cylinder insulation, heating controls, draughtproofing, new boilers, new windows or solid wall insulation will meet the requirement. For window replacement project only, only low cost measures are proposed to be triggered. These will be loft or cavity wall insulation, hot water cylinder insulation and draughtproofing. Occupiers of historic or conservation buildings should seek further guidance from English Heritage.

The only other proposal is that when windows are replaced B rated ones are used, instead of the current C rated.

Summary of the Part L changes as a whole

The proposed change to building regulations begin to pave the way to zero carbon new build dwellings and energy efficient existing homes. In summary:

  • The proposals as they stand will lead to new build dwellings in 2013 having 8% less carbon emissions than 2010 building regulations, in preparation for a 100% reduction by 2016.  This approach is preferred to a slightly more expensive approach that will achieve 26% carbon reductions.  Views are being sought on which approach is preferred by consultees.
  • A new Fabric Energy Efficiency Standard will be introduced to encourage housebuilders to adopt a fabric first approach.  This will be a new concept to builders who have no experience of the Code for Sustainable Homes.
  • Views are being sought on the “fuel factor” which influences the target carbon emissions that a new dwelling must achieve.  In any case, the fuel factor will not influence the target carbon compliance in 2016.
  • Views on a quality assurance standard are being sought.  Key items will be for overdesign of energy efficiency aspects of a new dwelling and post-construction testing such as co-heating tests.
  • All new dwellings will now be expected to make energy efficiency improvements, where economically feasible, when triggered by other notifiable works.


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