Suspended timber floor - renovation - UnderFloor Heating possible?

catharsis

I'm considering a renovation project on a 30s-built Semi-D in Dublin.

I know the ground floor is a 'ventilated' suspended floor in as much as there are vents from outside the house into the sub-floor space.

I realise I will need to insulate and draught-proof as a first step, but should I simply forget the possibility of under-floor heating as I would effectively be heating the ventilated space and hence the cold air would flow straight under the warm UFH and take away all of the heat?

Thanks in advance for any help/guidance.

C

BryanF

catharsis wrote: »

I'm considering a renovation project on a 30s-built Semi-D in Dublin.

1. I know the ground floor is a 'ventilated' suspended floor in as much as there are vents from outside the house into the sub-floor space. I realise I will need to insulate and draught-proof as a first step,
2. but should I simply forget the possibility of under-floor heating as I would effectively be heating the ventilated space and hence the cold air would flow straight under the warm UFH and take away all of the heat?

Thanks in advance for any help/guidance.

C

1. imho you either (A) install a new concrete floor super-insulated with external wall insulation to foundation or (B) insulate and seal at floor level retaining the below floor ventilation. B is cheaper than A - both mean realistically replacing all floor finishes
2. you wont be doing both. if you going with UFH best to remove the sub-floor ventilation requirement

atilladehun

Any idea of the cost of b? We have the same with loose soil underneath. We had to block up the vents to stop vermin now we've a damp problem.

BryanF

atilladehun wrote: »

Any idea of the cost of b? We have the same with loose soil underneath. We had to block up the vents to stop vermin now we've a damp problem.

depends on amount work to clear out, thickness of insulation & concrete, access to site, location in the country, details of radon barrier etc

my area is specifying and advise on the above - not really pricing it thats for a contractor or QS - from previous experience the issues of access & really contractor interest can be factor in a price of this type.

the presence of damp would also be a concern and one that would warrant further investigation before any concrete floor etc was installed

catharsis

We would be doing this while 'gutting' the house, so will at a minimum be removing the floorboards in order to install underfloor installation and draughtproofing. At the moment the floorboards are the only thing between us and the uninsulated ventilated underfloor space.

Some of the floors involved would be up to 4 feet above 'earth' level, from a quick visual examination. Does this make the idea of filling-in the entire sunfloor space impractical? And if so, does that make UFH a near-impossibility for us?

Thanks for the comments thus far.

Wally Runs

We had something similar, we have UFH on suspended floor, 4-5 foot above the soil, the house is on a slope. This is how it was done;

1. Floor joists strengthened and given extra depth.
2. Each space between the joist was floored with some ply.
3. Underneath the ply was filled in with rockwool and retained with netting. This was done from below the floor.
4. The upper part of the joist box was lined with that bubble foil?
5. UFH pipes laid and filled with screed.
6. Floor levelled and wood flooring on top!

All signed off by the structural chap!

Some thing like this: http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=6390

BryanF

Wally Runs wrote: »

We had something similar, we have UFH on suspended floor, 4-5 foot above the soil, the house is on a slope. This is how it was done;

1. Floor joists strengthened and given extra depth.
2. Each space between the joist was floored with some ply.
3. Underneath the ply was filled in with rockwool and retained with netting. This was done from below the floor.
4. The upper part of the joist box was lined with that bubble foil?
5. UFH pipes laid and filled with screed.
6. Floor levelled and wood flooring on top!

All signed off by the structural chap!

Some thing like this: http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=6390

Great post! how much screed went above the joists? ive seen this done where ply was placed above the joists, ufh and screed but never between? did this change the floor - ceiling height? did you need to change/ adjust the doors?

catharsis wrote: »

We would be doing this while 'gutting' the house, so will at a minimum be removing the floorboards in order to install underfloor installation and draughtproofing. At the moment the floorboards are the only thing between us and the uninsulated ventilated underfloor space.

Some of the floors involved would be up to 4 feet above 'earth' level, from a quick visual examination. Does this make the idea of filling-in the entire sunfloor space impractical? And if so, does that make UFH a near-impossibility for us?

4ft is alot of sub floor -Wally's solution above is interesting, depending on whether you were keen to keep the joists.

you could also look at building up posts out of blocks, then pre-cast beams with block infill, insulation followed by UFH & screed.

the current new build regs call for the equivalent of 140mm kingspan PIR for ufh (double that for mineral wool type products)

id be wary of ufh if the insulation continuity was going to be difficult at wall junctions

Wally Runs

BryanF wrote: »

Great post! how much screed went above the joists? ive seen this done where ply was placed above the joists, ufh and screed but never between? did this change the floor - ceiling height? did you need to change/ adjust the doors?

I have no idea of the screed depth, I am just the householder. I would guess between 7-10 cm, no height lost as the depth in the joists was built up from below. The screed came to the top of the old joists but did not cover them. There could have been a few mm of loss but the doors and architrave were all replaced anyhow. It is down three winters now.

I know that from below, when the heating is on, you feel below very little heat coming through. Having said that the heat is not on much, as the whole house was insulated etc.

kbfdirect

catharsis wrote: »

We would be doing this while 'gutting' the house, so will at a minimum be removing the floorboards in order to install underfloor installation and draughtproofing. At the moment the floorboards are the only thing between us and the uninsulated ventilated underfloor space.

Some of the floors involved would be up to 4 feet above 'earth' level, from a quick visual examination. Does this make the idea of filling-in the entire sunfloor space impractical? And if so, does that make UFH a near-impossibility for us?

Thanks for the comments thus far.

Would like to know how you got on, what you used and the cost as I am in the middle of a house refurb and face the same problem of insulating between the joists on a suspended floor.

Calahonda52

I think the idea of the netting underneath the rafters has now been superseded since there has been an increased understanding of how insulation actually works and the detrimental impact of air passing through the insulation, even horizontally across the surface in an attic.

Fibre type and loose insulation such as cellulose needs to be protected from wind so under the floor I would think the rigid insulation, properly cut and gaps sealed, is a better job more easily done.

The really tricky bit is at the ends of the joists, especially if they are just sitting on dwarf walls and stop about 1" or so from the wall.

Cables from sockets etc make it also tricky to seal up properly.