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| Walls - Issues To Consider - Timber Frame | |
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Timber frame walls as
traditionally constructed typically comprise 89 mm deep studs filled
with 90 mm mineral fibre quilt/batts. This construction achieved a U–value of 0.41 W/m².K* and thus achieves the requirements (0.45 W/m².K) of the old Building Regulations and Standards in all of the UK and Ireland. The new Technical Standards Part J (Scotland) requires a U–value of 0.27/0.30 W/m².K (dependant on SEDBUK rating) and the Building Regulations (England & Wales). Approved Documents L1 & L2 require 0.35 W/m².K for walls to comply with the elemental method of compliance. The change in U–values for walls provides an opportunity for specifiers to rethink the way they insulate timber frame walls. In order to achieve U–values of 0.30 and 0.35 W/m².K, 125/130 mm and 100/110 mm respectively of mineral fibre quilt/batts of the type currently used may be required. This would require an increase in stud depths to accommodate the insulation. In reality a standard size like 140 mm nominal would be used. Mineral fibre in timber frames relies on friction to hold it vertical and so a slight over–thickness is normally used. Therefore, a standard thickness of insulation, say 150 mm, would most likely be used. |
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There is a compelling
alternative that specifiers would do well to consider. Scotland 75 mm of Kingspan Thermawall TW55 zero ODP between 95 mm deep studs will achieve a U–value of 0.30 W/m².K. The additional cost of the 65 mm Kingspan Thermawall TW55 zero ODP option is 11% lower than that for 150 mm deep mineral fibre. |
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| England
and Wales 65 mm of Kingspan Thermawall TW55 zero ODP between 89 mm deep studs will achieve a U–value of 0.35 W/m².K. The additional cost of the 50 mm Kingspan Thermawall TW55 zero ODP option is 30% lower than that for 150 mm deep mineral fibre. |
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