When considering the performance of insulation in buildings, it is easy to forget the effects of ‘thermal bridging’, which refers to heat energy lost through un-insulated surfaces such as door and window frames, as well as timber stud frames in walls. This is where continuous insulation principles come in.
In framed wall constructions insulated with conventional glasswool batts, which do not overlay the frames, as much as 12 percent of the surface area of the wall will allow heat energy to leak through due to the un-insulated frames.
The NCC (National Construction Code) recognises the problem of thermal bridging, also known as ‘cold bridging’, throughsteel framing, requiring the use of a thermal break of R0.2 between the frame and cladding to reduce heat conductance, but there are no Australian building code requirements to address thermal bridging in materials other than steel. Whilethe typical NCC requirement for most climate zones in Australia is RT2.8, this rating does not take account of all types of thermal bridging. For instance, an RT2.8 framed wall system insulated with batts might actually perform with inefficiencies of up to 12 percent due to heat lost through the timber framework, i.e. at closer to RT2.4 levels.
By contrast, building codes in North America, UK, Europe and New Zealand all recognise this rating ‘loophole’ and include regulations to counter thermal bridging energy losses. The New Zealand Standard (NZS 4214), for example, calls for un-insulated framing materials to be considered, reducing achieved R-values by up to 12 percent or more.
To get more in depth information about continuous insulation, visit www.wholenewlight.com.au