Underfloor insulation - Advice needed

[davedon]

Hi there,
I have a 1950s house with suspended timber floors. There is a reasonable space for working underneath. The floors are draughty and cool, and the air bricks provide more than adequate ventilation. I started insulating using 200mm thick glass wool leftover from my loft insulation, and garden safety netting to keep it in place. The joists are 400mm wide.
I have attached a picture of the small area that I have completed. My concern is that it's not a very tight fit and the wool is sagging slightly. I was thinking of getting a breathable garden type membrane to lay over the netting, stapled to the joists. The other option was a foil based sheet like thermawrap, but I was concerned about blocking ventilation to the joists.
If anyone has any advice it would be much appreciated.
Cheers View media item 68709

 

[Burnerman]

I think thats fine.....obviously any draughts between floors and skirting need to be attended to, and keep an eye out for any damp ingress on the outer walls.
I use an expanded metal strip called builders band to keep the insulation tight against the floorboards - forced in between the joists.....works for me! Keep cables free of the insulation if you can.
John

 

[freddiemercurystwin]

Doh! The award for Inappropriate Choice of netting goes to davedon!

Chicken wire or something else more rigid would've been a better choice.

 

[AronSearle]

I think problem is that it looks like air could move along the gap between the flooboards and insulation, perpendicular to the joists.

This will reduce the effectivness of the insulation, I'm not sure by how much, but at the perimiter at least the effect will be very strong and will largely neture the insulation, maybe not so much of an issue further away from the wall.

 

[davedon]

Hi guys thanks very much for getting back to me.
I take your point Freddy about the netting. I got advice from another website and that was what was suggested. I think the builders band should do a job if it can push up the insulation to sit flush with the floorboards. This would stop the gap and air movement suggested by Aron.
Thanks all I really appreciate your help