Underfloor Insulation

cyclonebri1

I'll just add my bit to a very old post, newcomers would be advised that it is better for all to start a new thread under these circumstances although it's not criminal not to;);)

Anyway to all that complain about it being freezing cold and draughty under the boards, great, it's supposed to be, what do you expect?
It has to have airbricks as everyone has pointed out, and if it isn't cold at this time of year, well, you must be pumping heat down there:eek:

The 1 thing to make sure of is that you fix the insulation firmly in place, floors take a lot of hammer and if not rigidly in place the ins will sag.

If using garden netting as a support for f/g or rw then it needs more than light gauge rusting staples to hold it in place, use s/s staples and put roofing battens at right angle to the joists to hold the stuff up.

I'd go with thick Kingspan flush with the floor boarding nusing a mastic adhesive as insurance ;)

Martyn_H

Thanks for tips but still would like to know which thickness will conform to heat loss regs.

cyclonebri1

I don't think you need to bother with the regs on this one, it's not a new build, just improvement work.

As much as is reasonably affordable would be my answer.

One last point, if you do this and effectively have sealed the room, just remember that you do need some ventilation/air change in a living room, you can't live in a "vacuum":D

Martyn_H

Good points. I'll see if I can get 6" between the joists, without blocking the underfloor vent for the gas fire.

cyclonebri1

Martyn_H wrote: »

Good points. I'll see if I can get 6" between the joists, without blocking the underfloor vent for the gas fire.

:eek::eek::eek::eek::eek: Glad I made my last point, take care;);)

Waz5

Hi,

I'm looking for some advice as we are planning to do up our living room and I thought it would be a good idea to do floor insulation in the process. We have an old 1900's house and get alot of cold air around skirting board area on external wall side (plan to look at this while doing the room up). We have cellar underneath the living room.

I am planning to use Kingspan Thermafloor TF70 for insulation. Anyone use this or recommend anything better for floor insulation?

Also how much air gap should I leave and should that be at the top or bottom (I'm planning to put insulation by lifting the floorboards)?

We have cold external wall (solid stone), anyone know what I could use in the inside to insulate it?

Many Thanks

Waz

new_owner

Waz5 wrote: »

Hi,

I'm looking for some advice as we are planning to do up our living room and I thought it would be a good idea to do floor insulation in the process. We have an old 1900's house and get alot of cold air around skirting board area on external wall side (plan to look at this while doing the room up). We have cellar underneath the living room.

I am planning to use Kingspan Thermafloor TF70 for insulation. Anyone use this or recommend anything better for floor insulation?

Also how much air gap should I leave and should that be at the top or bottom (I'm planning to put insulation by lifting the floorboards)?

We have cold external wall (solid stone), anyone know what I could use in the inside to insulate it?

Many Thanks

Waz

Insulation should be flush against the floor boards.

You need to think about what happens if liquid is spilled onto the wooden floor and you have a vapor barrier underneath (TF70). Is your cellar heated?

You need to be careful with an un-breathable insulation in an old house. Think cold bridge.

Waz5

new_owner wrote: »

Insulation should be flush against the floor boards.

You need to think about what happens if liquid is spilled onto the wooden floor and you have a vapor barrier underneath (TF70). Is your cellar heated?

You need to be careful with an un-breathable insulation in an old house. Think cold bridge.

Thanks that's a very good point. The cellar is used as a utility room at the moment but no it's not heated regularly. There is heater fitted in the cellar but like I said it's hardly ever used.

cyclonebri1

new_owner wrote: »

Insulation should be flush against the floor boards.

You need to think about what happens if liquid is spilled onto the wooden floor and you have a vapor barrier underneath (TF70). Is your cellar heated?

You need to be careful with an un-breathable insulation in an old house. Think cold bridge.

Cellotex or Kingspan is always recommended for this application, I don't think there are any issues, it certainly isn't going to give any cold bridge effect.

If you are going to the expence of decent insulation, which isn't cheap, rather than rockwool which is cheap, but is much less effective and much more difficult to ensure it's held securely in place, then go the added mile and nail or screw roofing battens or any cheap sawn timber to the joists as a support to ensure there is no possibility of that expensive insulation falling out when you have a party in full swing above:D:D.

new_owner

cyclonebri1 wrote: »

Cellotex or Kingspan is always recommended for this application, I don't think there are any issues, it certainly isn't going to give any cold bridge effect.

If you are going to the expence of decent insulation, which isn't cheap, rather than rockwool which is cheap, but is much less effective and much more difficult to ensure it's held securely in place, then go the added mile and nail or screw roofing battens or any cheap sawn timber to the joists as a support to ensure there is no possibility of that expensive insulation falling out when you have a party in full swing above:D:D.

Cellotex or Kingspan are recommended for newish buildings not older buildings which have 1 requirement, breathing. It will certainly cold bridge on a sub vented floor.

Fibre board, sheeps wool, hemp are a the ones that spring to mind that will work with an older vented building. Man-made materials are very good at insulation but not at dealing with moisture and as for cost... kingspan vs sheeps wool is around the same price.