Reroofing? Time to upgrade the insulation as well…

08/05/2017

Reroofing 50%+ of the original roof? 

Reroofing over a room in the roof or vaulted ceiling? Did you know that if you’re reroofing more than 50% of the roof then Building Regulations require you to upgrade the insulation at rafter level to current standards  - a U value of 0.18 W/m2K  - if the existing insulation is worse than U 0.35 W/m2K.

But U-0.18 W/m2K isn't always possible?

However, very often this just isn’t possible – if your rafters are only shallow, or you can’t raise the roof – and in that case you must at least show an improvement. You might think the obvious thing to do would be to fully fill the rafter space with insulation? However that can actually create a condensation risk if the moisture coming up from the house below can’t escape quickly enough at the coldest point under the breather membrane.

No need to counter batten?

tlx gold installed draped over the raftersTLX Gold is an insulating breather membrane which can be draped over the rafters without the need for counter battening. Combined with 50mm of PIR in 100mm deep rafters it will achieve U = 0.33 W/m2K, and there’s no condensation risk - even without a vapour barrier below - because of its breathability. If the rafters are really shallow or irregular and you can’t fit any PIR board between at all, then TLX Gold can simply be draped over the rafters (with the usual 10mm sag between them) just as for a conventional breather membrane – but providing some insulation at the same time! You need to allow a minimum of 50mm of rafter depth for the product plus the heat-reflecting air gap if used in this way; and since TLX Gold has a BBA Certificate you can be sure that it will perform as claimed.

Click to view our LABC registered TLX Gold (draping) solutions

You can view a case study demonstrating this in practice HERE

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