Roof insulation

[Jacob]

Having our roof stripped and new tiles. They are talking about insulating quilt laid over the rafters i.e. all insulation applied from the outside instead of sarking etc.
I know nothing about these quilts.
Any opinions?
Will I still need rigid insulation between rafters, which I'm used to doing, (Kingspan etc)?
Any particular brand names for quilts, or other links?

 

[HOJ]

Don't quote me on this, but from what I am reading up on, for my own Catslide roof, The multifoil solutions are used in conjunction with other layers of insulation.

I am looking at products from: Actis at the moment.

 

[Mrs C]

We had a new roof recently and the roofer used TLX gold insulation. It is a sloping roof on a very old house. From memory the tiles and battons came off. TLX, then battons and tiles went on. The plaster and paint on the inside remained untouched, no other insulation in between.

Its made a huge difference

 

[Jacob]

Thanks for replies.
Seems to be effective by all accounts.
Question would then be how much PIR extra insulation would I put between rafters behind the plasterboard.
Maybe just go for it while we can and see how it turns out - can't be done retrospectively.
https://www.insulation-actis.com/fi...t/JN_2763 Actis HControl Hybrid Datasheet.pdfhttps://tlxinsulation.co.uk/tlx-gold-should-i-use-it-draped-or-counter-battened/

 

[Mrs C]

Personally I would put as much as you can as long as you maintain the air gap between the top of the insulation and the next layer.

I have just finished 50 + square meters of insulation the garage roof, 140mm, I never want to do it again in my lifetime. Hence suggest you do the the best you can afford and then forget about it.

P.S. Before anyone asks hubby developed a mysterious allergy to kingspan and I was too mean to pay someone else to do it.

 

[Doug71]

Used just Actis Triso on my old school conversion in about 2007, it was banned for a while after that, think something to do with Kingspan and a Hotbox test. My place has nice roof trusses with wooden boarding on top which we didn't want to cover up so the insulation had to go above and anything else would have raised the roof height too much.

I'm not convinced it's that great though so would definitely add Kingspan while you can.

 

[Jacob]

Mark Brinkley House Builder's Bible says Actis and similar are still a bit contentious but obviously have some value.
Minimum PIR for building regs is 200mm apparently but this not easy under the rafters. Maybe have Actis under the tiles, 50mm Kingspan between rafters, 50mm counter battens with 50mm Kingspan between them, foil backed plaster board to the battens.

 

[Jake]

Fully warm roof is the easiest to get right detail wise, cold and hybrid ones are much harder to get right vapour/condensation wise.

 

[Jacob]

Fully warm roof is the easiest to get right detail wise, cold and hybrid ones are much harder to get right vapour/condensation wise.

Yes the quilt won't work unless well attached all round the edges as cold air getting in the space would cancel it out.
Draughts can bypass and completely nullify insulation.
Whereas PIR tight up behind plasterboard has no voids for cold air to get into.

 

[BarbaraT]

The quilt is quicker to lay and I would guess a lot cheaper.. I would guess performance-wise it's pretty poor.

I was comparing rockwool to rigid pur foam a while ago and to get a similar level of insulation you needed so much rockwool it actually worked out more expensive.

Crunch the numbers with what they plan on using and see how it compares. Latest building regs say you should have 0.15 W/m²K or less for a roof.

Instructions are here, and numbers are here.
https://en.wikipedia.org/wiki/R-value_(insulation)

 

[rs6mra]

not long finished on a project of 11 houses and all had the insulating quilt laid over as well as 100mm Knauff insulation in between the rafters.

 

[Cobbs]

Whatever you use, just make sure it doesn't lift the felt to be in contact with the battens between the rafters - the felt needs to sag to allow any water that gets in through broken slates or whatever to run away without being directed towards the rafters, where it would eventually sit behind the battens and rot them out. There always needs to be a sag in the felt between rafters with no felt touching wood except where it's pinched between batten and rafter.

 

[Krome10]

Just to be clear...

Is it a vaulted ceiling (i.e. no loft space)?

What is the rafter depth?

Do you have beams, A-frame, etc that you want to leave exposed on the inside?

What are the current and proposed ventilation requirements?

I'm no expert but having done a fair bit of reading on the subject I'm happy to share anything I've learnt that may help....