Moisture permeable solid insulation

[Lostgardensof]

We are putting underfloor heating in a section of the house with a solid floor (over a stone vaulted basement). The plan is to make it all vapour permeable to prevent damp issues I.e limcrete and tile with lime grout. Can anyone recommend a type of insulation to use between the current packed rubble and the wet underfloor system to direct the heat upwards?

 

[MikeG]

I presume you mean vapour-permeable rather than moisture permeable?

I think that what you describe is the el dorado of the insulation world: always just over the next hill, just around the next bend.

 

[Lostgardensof]

Yes. I mean vapour permiable. So it doesn't exist? Hmm.... Any work arounds? Like leaving a channel round the edge of the floor where there is no ufh and filing that with something like rock wool and covering with vapour permiable board before tiling? Whilst using cellotex for the middle bit of floor?

 

[MikeG]

Yes. I mean vapour permiable. So it doesn't exist? Hmm.... Any work arounds? Like leaving a channel round the edge of the floor where there is no ufh and filing that with something like rock wool and covering with vapour permiable board before tiling? Whilst using cellotex for the middle bit of floor?

You're trying to mix oil and water. I'm afraid these sort of issues need to be thought through before committing to Limecrete.

 

[Lostgardensof]

Hence my request for advice. Any ideas anyone?

 

[MikeG]

Yep: radiators.

 

[MikeG]

Thinking this through.....

..........is the entirety of the floor above the cellar/ basement? If so why are you worried about damp, and considering putting in Limecrete? You could just ventilate the basement properly, even if that means mechanically and via ducting, then put in a concrete base, Celotex insulation, and screed with underfloor heating. Of course this doesn't apply if your floor is only partially above the cellar and is in contact with the ground elsewhere.

 

[Lostgardensof]

The whole floor has cellar underneath but the ground level outside rises above the floor level so I suspect there might be possible damp issues. Radiators and a suspended floor with air ventilation between the floor and outside?