Another insulation question, sorry

[Nimster]

Morning

Sorry, it's another insulation question. Apologies in advance

Our cottages are freezing. We suspected the roof was not insulated to took down a section of plaster to check. This revealed thin rubbishy polystyrene "insulation". We're going to take the ceilings down and insulate it properly but we can't decide what's best to use. The bedroom ceilings are currently open to the apex with fully exposed beams, and we would like to keep these exposed. This obviously means that any insulation has to sit between the beams. Would we be better going for Kingspan or one of the multilayer foil insulations like this:

http://www.roof-solutions.co.uk/ourshop_158894_cat23370.html

We can use up to 80mm of Kingspan without losing the beams, so thickness isn't really an issue. I've rang the various companies to ask their opinions and, predictably, they all say theirs would be the best product :roll: .

Any suggestions (other than moving house)?

Thanks
Nim

 

[Nemesis]

Well - the foils debate is I think still raging... at least on the 'old' GB Forum...


http://www.greenbuildingforum.co.uk/forum/index2.php?DATEIN=tpc_wlpssdlpg_1142805843

 

[Lime]

I wouldn't touch foil.

 

[Nimster]

So what would you use Lime? We need something with high insulating properties - the cottages are freezing (we're talking 8 degrees at present) - 3 down duvets and an electric blanket, and I'm still waking up cold

 

[MdB]

This revealed thin rubbishy polystyrene "insulation".

Check any wiring that is in contact with the polystyrene as the PVC in the wiring insulation can be damaged by it.

 

[biffvernon]

Don't use multifoil.

If space is the most important factor and money is no object then use 'Spacetherm'. It is an aerogel blanket that has a thermal resistance of 0.013w/mk That's almost twice as good as the best rigid foam products. It comes in sheets 10mm thick but costs almost £20 per square metre.

 

[Nimster]

Don't use multifoil.

But why?

Assuming that space isn't an issue (we can easily put 100mm of insulation behind the plasterboard) but that money IS an issue what would you use?

I did a quick hunt for Spacetherm and their website quotes ~£80 per sheet - while I want a warm house, I would like to be able to eat for the next year too!

 

[Johneds]

There are doubts about the efficiency of multifoil insulation. It obviously has some useful properties and may be a good alternative in some circumstances but I don't think that applies to your situation.

If you can accommodate 80mm I would personally recommend a PIR foam insulation. e.g. Celotex, Kingspan. You do need to be careful about ventilation though. Really you need a vapour barrier (not really practical if you want the rafters exposed) or ventilation behind the insulation.