Elect. Radiant Heat on existing slab etc
New to the forum –
I’m seeking advice on the following installations for a renovation on Shelter Island, NY:
1) Existing conditions: uninsulated conc. slab w/ linoleum flooring (circa 1980)
New: install (cork?) material over linoleum as thermal break, then electric radiant heat matts (Nuheat or equal) in thinset bed & large format stone tile as finish floor.
questions: is cork an appropriate underlayment? what adhesive would you use between linoleum & cork (or other underlayment)?
2) Adding new cedar shingles over existing sheathing – what is best practice for a back-vented rainscreen type of installation? what is best building paper product?
3) For a stone-surfaced exterior terrace, dry laid over sand and gravel bed, what is a good durable stone to use for this climate that would also be appropriate for interior application as tile?
Replies
Greetings SH,
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
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On #1, an appropriate underlayment would be at least 2" of XPS foam, above which would be a good vapor barrier, then the slab. Too late for that now, unless you jackhammer the floor and start over. Trying to provide the equivalent insulation value with a thin layer of cork over the linoleum doesn't work. Your heat loss to ground will be enormous, and at electric costs??!! Then there are the moisture issues with cork to consider. How much ceiling height can you afford to lose by adding thickness of stuff over the present floor?
To clarify, the radiant is not meant for primary heating, just for "warm toes" - also, we have a condensation problem on the current slab, since its uninsulated, and are using the radiant as a way of keeping the flooring dry in hot humid weather ( I know it seems antithetical, but it works). We just want a material that will break the conductive transfer of energy from slab to flooring, and something that will be a stable underlayment for the new tile floor.
You can bond Wedi Board to the slab with thinset and put your heating mat above that. Wedi has insulation value and is spec'd for floor installations. It can be hard to find and it's expensive now.
For toe-warming on older slabs most people bond the heating mat to the slab and put Ditra above it for crack suppresson, and then tile.
Ask over here:
http://www.johnbridge.com
Billy