Kingspan / Celotex under screed

[jasont247]

Hello,

I am building a single storey sun room at the back of my house. Because of the soil it is built on a raft foundation. We have laid the sub floor 8m2 of concrete and mountains of steel.

For the insulation between the top screed and sub floor is it worth the extra money using Kingspan / Celotex instead of polystyrene.

The insulation will be about 60 to 70mm
Kingspan will cost £200, cheapo stuff is about half.

We will have carpet in the room.

 

[freddiemercurystwin]

Polystyrene is crap, that's why its cheap. You would need about twice the thickness to archive the same resistance. You could have gone the poly route if you used twice the thickness and had thought about the thickness before you poured the slab.

 

[Deluks]

Depends what you mean by 'sun room' and what you expect it to do.
I wouldn't use a sun room in the winter when there's no sun, too cold! So if this really is just for warmer weather use then the poly will suffice.

 

[dylanp]

I am in the process of converting my garage into an additional room. I used 100mm PIR insulation under the screed. I found Encon the cheapest supplier. They were cheaper even than online companies selling 'cheap' seconds. I believe they were £25 p 100mm sheet compared with £35-£40 everywhere else I tried.
http://www.encon.co.uk/branches

 

[dylanp]

I wouldn't use Poly insulation: it is about 5 times less effective and only half the price ... It should be 5 times cheaper than PIR!!

 

[noseall]

Poly insulation: it is about 5 times less effective

not true

 

[dylanp]

Poly insulation: it is about 5 times less effective

not true

OK, simply passing on info I've been advised in the past.
Incidentally, do you have any idea what the actual ratio of efficacy is between Poly and PIR?
Thanks

 

[freddiemercurystwin]

More like twice:

http://www.spray-insulation.co.uk/Insulation_efficiency.htm

 

[dylanp]

More like twice:

http://www.spray-insulation.co.uk/Insulation_efficiency.htm[/quote

Good to know, thanks.