Dáil Éireann Debate, Tuesday - 12 December 2006
170 Mr. Boyle asked the Minister for the Environment, Heritage and Local Government the details of research, correspondence or advice that his Department has received relating to the possibility that different measurements resulting from the use of the overall heat loss method and the elemental method of measuring compliance with Part L may be leading to different outcomes depending on the method used. [42608/06]
Amharc ar fhreagraI assume that the Question refers to a report (30 May 2006) by the UK based Building Research Establishment (BRE). The report sets out a calculated comparison of the above two methods of achieving compliance with Part L for a small sample of two English dwellings. My attention was drawn to this report in correspondence from the timber frame manufacturer who commissioned it.
In its conclusion, the BRE report claims that houses built to comply with the elemental method will use about 30% less energy for space heating than those complying with the Overall Heat Loss (OHL) method.
My technical advice is that the two methods referred to in the Question undoubtedly give different results. The differences depend on the type, size and shape of the building and on the actual areas of the main external elements, i.e. roofs, walls, floors, windows and doors. However, I am advised that the differences between the two methods should be significantly less than claimed for the two English examples. The BRE Report does not contain sufficient information to allow independent review and validation of its assumptions and calculations.
The May 2006 edition of Technical Guidance Document L includes both methods of demonstrating compliance with Part L (Conservation of Fuel and Energy) of the Building Regulations. The primary reason for allowing both methods is to provide options for:
some flexibility in how heat loss through the building fabric is limited, via the OHL method, and
a simple method — the Elemental method — of demonstrating compliance which suits those who do not wish to deal with the complexity of additional calculations.
Part L standards for Dwellings are due for revision in 2008 at the latest, as required under the EU Energy Performance of Buildings Directive. In this context, the appropriateness of continuing the two methods will be considered.
