Insulating a floor

[Garald]

As I said in another post: I got a list of suggestions from the "energy audit" (this is a requirement to get subsidies for energy-efficiency improvements in France) and I've gone over it with my architect.

 

One suggestion is to insulate part of the floor in the ground floor. (My apartment is mostly in the first floor and attic; it also contains a chunk of ground floor, but it's almost entirely service rooms at present (garage, laundry) - we will make what is now the laundry into an office/guest bedroom. The insulation suggestion would apply to that office/guest bedroom and to the entryway. They are apparently above a basement that belongs to other people.) More specifically, the suggestion is to add 120mm of expanded polystyrene.

 

My architect says that that's quite mad - we would have to go at it with a jackhammer, with the possible risk of making the ceiling of our neighbours' basement cave in.

All we can do is add between 20 and 30mm of insulation before laying on a new floor (our plan is to use hardwood).

 

What would be the best sort of material to use in those 2-3cm?

 

(We are talking about 21m^2. We won't insulate the floor in the garage (= future bike-shed and laundry room) - it is partly earth, and at any rate we will insulate the garage's ceiling instead.)

 

[JohnMo]

If your only doing 20 to 30mm PIR or similar.  You could do aerogel but not sure the cost v reward would be worth it.

[Garald]

Right - my architect is now suggesting 25 to 30mm of TMS polyurethane or Utherm Floor K (PIR). 

 

She was telling me that, ironically (it took me a moment to realize she said "ironically" because "pire" means "worse" in French),

PIR has a reputation as being "not as bad" as polyurethane. I imagine that that means that we will go with PIR.

 

In either case, that apparently means we will not have hardwood :(. It's wineo (www.wineo.de) for us at that level. Sad...