Loft insulation, a reminder, please.

[woolybanana]

I have discovered that part of my loft space has never been insulated, but that there is a big roll of that multi-layered thin stuff ready to be put up.

Thus far, opinions received as to its efficacity are mixed but I was wondering whether anyone on the forum has used it (Chancer?) and whether they think it is any good? Or should I use traditional rockwool or fibre glass. Or simply double the thin stuff?

Thoughts gratefully received.

[Chancer]

I used it on les combles, its not as effective as laine de verre particularly against summer heat, its advantage is that it is thin.

 

You will need more than one roll anyway so use laine de verre, mind you that is at least €4/m2 in France, a shocking price, I am just coming to the end of the 99p a roll subsidised UK insulation, its been sitting around for years but it looks like I estimated well.

 

If you have it then use it, it can only help, you can then add laine de verre above it.

[Théière]

Wooly, the multifoil's plus is providing its installed properly it seals the space from drafts and the foil face can either reflect the heat of the sun off the roof making it cooler inside or used the other way reflect the heat internally to keep it warmer in winter.  It does not replace the bulk of a fiberglass or rockwool for actually keeping the heat in but then again you need a really good thickness of fibreglass or rockwool to achieve similar heat retention as neither of the wool types do a particularly good job of sealing the space from drafts plus you simply not have enough space for a really thick wool.

Combining a multifoil layer and a glassfibre or rockwool layer gives the best of both and that can be thinner that way.

I am using multifoil and 200mm of rockwool in my roof, with the multifoil on the outside to reflect the heat of the summer.  This should give a U value of 0.16 W/m2 k and I couldn't fit 300mm of rockwool in anyway.

[Jonzjob]

I have that in the roof of my workshop, but mine is 5 foil layers and silver on both sides. I got it from a company in Grenoble and it was quite expensive, but it works and works well.

[8-|]It keeps the heat both in and out so, if it's free then why not use it??

[woolybanana]

Thank you chaps, will digest and react.

[mint]

No, Wools, don't eat it, nevermind digest it!  C'est pas comestible, alors[blink]