Energy Efficiency Best Practice in Housing for home extensions
Effective use of insulation in extended dwellings
A guide for specifiers and contractors.
Insulation is a fundamental element of any energy efficiency strategy for dwellings.This guide describes the levels likely to be needed to meet current best practice.
- best practice
The Best Practice specifications for extending dwellings.
- new housing and extensions
The Best Practice specification for new housing includes Carbon Index (CI) targets. The Index is an indicator of the carbon dioxide emissions associated with space and water heating and is expressed on a scale of 1-10; the higher the number, the better the performance.
- insulation tables 1
Table 1: Carbon Index requirements for various domestic heating fuels for home extensions.
- insulation tables 2
Tables 3-5:Typical insulation levels required to satisfy the Best Practice specification for home extensions.
- extsing housing
Refurbishment work on dwellings tends to focus on particular parts of the structure rather than the building as a whole.
- U and R values
Best Practice insulation specifications are generally expressed in terms of a U-value.This is the overall rate of energy transfer through 1m2 of a particular building element when the air temperatures on either side differ by 1ºC.
The following tables give examples of how to achieve Best Practice in refurbishment and home extension projects using appropriate levels of insulation.
- roof insulation
Lofts: An uninsulated loft space would have a U-value in the region of 2.5 W/m2K.With 100mm of insulation (λ = 0.040 W/mK) this improves to 0.4 W/m2K. Insulate (or top up) with two layers, covering the joists, to achieve a U-value of 0.16 W/m2K.
- environmental considerations
There is a growing urgency to reduce the environmental impact of human activities. Energy efficiency initiatives over the last 30 years have reduced the energy consumption of new dwellings considerably, but action to minimise the impact from construction materials has been relatively slow.