TLX Gold & Warmshell

[leucothea]

I’m re-laying my front roof, with existing tiles where possible, and I’m thinking to insulate with TLX Gold draped between the (original 1741) rafters and then adding 4cm of Lime Green Warmshell wood fibre board to the inside, under the rafters, with some lime plaster.

(The rear roof, which I won’t relay, was done in the 1980s, with felt but no meaningful insulation.)

This approach has been recommended to me but I’m skeptical it meets current building regs re. thermal performance.

I’m wondering whether people think the approach is sensible and whether anyone has any thoughts about how to approach building regs (or indeed whether I have to)?

I feel like I shouldn’t have to put masses of thick insulation on the inside just because I’m relaying the roof! And TLX Gold + Warmshell will be radically better than what I have now—quite a breeze through the attic on windy days!

 

[Lacan07]

Why not just do the usual 'cold roof insulation' along the floor of the joists? Are you planning on using the loft space for anything other than storage? Its not a bad thing to have a 'breezy attic'.

I don't know exactly what the score would be if your house was listed but if it isn't and your not subject to a building control notice (not likely for roofing) then you can do whatever you want.

I have a pitched ceiling on some of my upper floor and I chose steicoflex between the rafters and 100mm rigid foam board on top with all joints, fixes and junctions sealed air tight, as is necessary with a 'warm roof insulation'. The idea is you don't allow the warm moist inner air to pass through the insulation to the cold surfaces beyond where it will condense. I'm not entirely sure how a fully breathable system compromised of wood fibre and lime would be affected by this principle? One could say condensation may well occur (if the difference between the warm side and cold side is great enough) but being breathable it will easily dry out.

I choose a mixture of breathable / non breathable materials because I wanted to achieve s decent thermal performance in an area of the house that was basically lime plaster, felt and tile.

 

[leucothea]

Sorry, I should have mentioned—it’s Grade II listed and I’ve applied for listed building consent. The attic is large—in use as a couple of rooms—and there are nice exposed purlins that I wouldn’t want to lose behind thick insulation.

I got the impression that any extensive roof work would have to involve building regulations and that would mean bringing it up to modern standards (unless one received some kind of exemption)?

I would imagine with the configuration I posted, there would be a small amount of airflow into the gaps between the rafters and around the TX Gold, which is obviously breathable, and would also be vented at the ridge.

Thanks for your response and explanations. I find insulation a confusing area—too many options!

 

[LadyArowana]

We are also GII and when we had the roof done, all with LBC, building control basically said ‘do your best’ and weren’t any more interested than that!

 

[leucothea]

That's good to hear—thank you!