Floor insulation - suspended timber floor

vallo

I have a 70 year old house with suspended timber (pine) floors (not tongue and groove). When the wind is coming from a certain direction you can almost feel the draft coming up through the boards.
I am thinking of getting a job done on this in the next few months and am wondering what my options are.
I know that I can't just block off the vents, but would it be possible to take up the floors and seal the whole cavity underneath so that there would be no buildup of condensation/rot in future? Are there any materials that could be used in an existing building for this.
I want to avoid the cost/mess of filling the whole cavity with concrete (although this could be an attractive option with flood waters creeping higher each year).
What about other alternatives - is there something I could lay between the joists and the new floorboards?
Any suggestions welcome.
Thanks for reading!

MicktheMan

One option is to remove the floor boards, lay fibre insulation between the floor joists (full fitting) supported with light weight strong netting fixed to underside of joists. Next lay an air tight membrane over the floor joists and insulation taped (air tightness tape) at joins and to the walls. Re-lay floor boards. Your floor will still be ventilated but without the draughts.:)

vallo

That sounds like what I need! Thanks.
Are there any specific products you'd recommend?

Wally Runs

You may not need to remove all your boards. If there is enough room to crawl under the floor you could do it all from below. A potentiality tight and mucky job but better then lifting all the boards. I had a 3-4 foot space under mine.
Fibre-glass (rock wool might be better)
Garden netting
Staples and staple gun
Any membrane (breathable) Moy isover comes to mind.
tape

vallo

I'm pretty sure you couldn't get under the boards - the gap is probably 30cm at most!
Thanks for the pointers. I think I will definitely do it before next winter.

eboarde

I'm hoping to do do this from under the floor i.e. not lift the floor boards. Are the following steps correct?

1. Fit airtight membrane underfloor and joists keeping tight to floor and tape edges.

2. Snugly fit fiberglass/rockwool between joists but do not crush

3. Fit net below to stop rockwool falling out

If so:

How do I fit the airtight membrane? Can I staple it or will this just allow air through? Do I staple and tape?

If the airtight membrane is going below the joists then how do I fit the net? Staple and tape?

Thanks,

eboarde

MicktheMan

Depends really on how much room you have to move in but best way might be to staple the airtight membrane and cover staples with airtight tape.
I wound also staple/tape the netting.

There is also a double sided tape you can get but this might be diffucult to do if space/manoeuvrability is limited.

BryanF

eboarde wrote: »

Are the following steps correct?

1. Fit net below to stop rockwool falling out

2. Snugly fit fiberglass/rockwool between joists but do not crush

3. Fit airtight membrane above joists and tape edges. staple (and tape if required)

**** make sure you retain good ventilation of below the above floor build up ****

kbfdirect

Hi All, does anyone know if 4 inch Styrofoam fitted between the joists is a good job? these can be supported by 2x1's along the joists.