I'm installing a raised floor (aprox 5m^2) over a concrete slab. There's enough heat loss through the slab, to make it worth insulating between the joists.
Some websites I've seen mention adding a breather membrane under the insulation. Some say it's not necessary if using someting like foil coated Celotex.
1) Opinions on whether the membrane is needed?
2) If it is needed, is Option B a bad idea, or is A the only way to lay the membrane?
3) Are the breather membranes sold for roofing suitable?
https://1drv.ms/u/s!AiSdxKZH7MXJgTW9h7XV-y29Z0CZ
Some websites I've seen mention adding a breather membrane under the insulation. Some say it's not necessary if using someting like foil coated Celotex.
1) Opinions on whether the membrane is needed?
2) If it is needed, is Option B a bad idea, or is A the only way to lay the membrane?
3) Are the breather membranes sold for roofing suitable?
https://1drv.ms/u/s!AiSdxKZH7MXJgTW9h7XV-y29Z0CZ