Suspended wooden floors - making room warmer

Chris_F20

Hi Folks. Have read loads online about how to insulate and draught proof ground floor with suspended wooden floors. The house is pretty cold with the draughts from below.

I had been looking at doing the job right - taking up the floors, insulate between joists, and use a membrane to stop draughts. Seems like very messy job, labour intensive and also the success depends on how reliably the work is executed (I suppose like all work really).

The more I read, the more I am convinced that stopping the draughts is the key/single most important thing to addresss.

We're also keen on switching from floorboards to carpet. I came across a suggestion of laying 6mm ply over floorboards. Tape the edges to the skirting boards (or remove these and tape to walls). Then put down underlay and carpet. Seems like a fairly mess free/reliable solution to making the house more snug.

Anyone done this? Thoughts? I know the purists will say this is not insulation. But it should have a pretty good overall impact.

the_pen_turner

Stopping the air moving between a bove and below the floor is only a good thing but only if you maintain enough ventilation under the floor to stop it rotting and growing mould.

It's only a small mess now to insulate it properly. Do it wrong and you will have a much larger mess in a few years

Personally if you take it up I would concrete it with plenty of insulation as well

Chris_F20

Wasn't thinking about taking up the existing floor, rather laying 6mm ply on top of existing floor.

I would have thought it would be fine re ventilation, air still would circulate below as it does now, albeit not coming up through the boards. Plenty of ventilation in the rooms now.

Chris_F20

The alternative is to do this properly, lift the boards with the intention of re-using them. Use the following to do the job properly:

- breathable membrane to lay insulation in between joists
- breathable insulation between joists
- airtight membrane on top of joists
- airtight tape for taping membrane to walls, over staple marks etc

If I was to re-lay board by screwing them in, wouldn't I be breaking the airtight seal?

Lumen

Having done the rockwool-between-joists approach a couple of times, if I was doing it again I think I'd use rigid foam insulation (EPS or PIR) between the joists and simply taped two ways to the top of the joists, then membrane flat over the top and taped to the walls, then foam joist strips, then OSB then the final floor.

Chris_F20

Lumen wrote: »

Having done the rockwool-between-joists approach a couple of times, if I was doing it again I think I'd use rigid foam insulation (EPS or PIR) between the joists and simply taped two ways to the top of the joists, then membrane flat over the top and taped to the walls, then foam joist strips, then OSB then the final floor.

Can u clarify what you mean by the bold bits? Sorry if I am being thick!

I thought cutting & fitting the rigid insulation might be a total pain in the ass, messy/labour intensive. Filling gaps could take a lot of caulk (or whatever) if inclined to do so, but I haven't done it.

MicktheMan

Chris_F20 wrote: »

If I was to re-lay board by screwing them in, wouldn't I be breaking the airtight seal?

No, assuming proper woven membrane is used.

BryanF

Chris_F20 wrote: »

The alternative is to do this properly, lift the boards with the intention of re-using them. Use the following to do the job properly:

- breathable membrane to lay insulation in between joists
- breathable insulation between joists
- airtight membrane on top of joists
- airtight tape for taping membrane to walls, over staple marks etc

I did this, Warmest room in the house.

Chris_F20

BryanF wrote: »

I did this, Warmest room in the house.

I wonder how this approach might stack up cost-wise with cutting out the joists and backfilling, dpc, insulation later, cement/screed. Wouldn't be interested in underfloor heating. Less labour intensive than insulating between joists, but maybe more expensive materials?

S'

Good guide here: https://www.ecologicalbuildingsystems.com/Ireland/Blog/Post-Detail/A-Best-Practice-Approach-to-Insulating-Suspended-Timber-Floors

Calahonda52

Chris_F20 wrote: »

I wonder how this approach might stack up cost-wise with cutting out the joists and backfilling, dpc, insulation later, cement/screed. Wouldn't be interested in underfloor heating. Less labour intensive than insulating between joists, but maybe more expensive materials?

.
Clearly no intention of doing the concreting work yourself!!

Chris_F20

Calahonda52 wrote: »

.
Clearly no intention of doing the concreting work yourself!!

Point taken, I don't know what I am talking about - I have visions of a truck pulling up outside & simply piping in the concrete. As opposed to having to individually tack & baton the membrane to each joist, fill each gap with insulation, lay airtight membrane, tape over staples/to walls etc. Seems like a huge amount of work.

No even sure concrete is needed, this would be for back fill to bring the level up to where it needs to be to put down insulation and maybe hardboard or ply or whatever to fix floor to.