Insulating suspended floor

[jassdhali]

Guys,
1950's house with suspended floor with a space below the floor of about 900mm ( enough for me to crawl about in).
As there are ventilation bricks to keep timber aired, during winter floor gets pretty cold.
I want to add some insulation underneath in between floor joists, whats the best type of insulation and more importanlty do I need to to keep some sort of air gap above?
Thanks

 

[Blagard]

Almost any sort of insulation will help, it's more a question of how you get it in and keep it there. I would consider using something like rockwool bats pushed up to the underside of the boards, then something to keep them there. I have heard of people using netting stapled to joists or battens. check the spaces between the joists if you use bats. You can trim them down if need be before working under the floor. Use them trimed a bit oversize so you can initially get them to stay in place as they squash a little. There are lots of ways, and different materials. Jablite and similar might be better as cleaner to work with. No need for a gap between boards and insulation. Also do not obstruct any airbricks.

 

[^woody^]

Loft quilt (200mm) is currently on offer at B&Q for something like a few £'s a roll, so this would be better (ie more cost effective) than paying for anything else.

Also quilt is potentially easier for fit than board - use lath, or galv. mesh or plastic garden netting

 

[jassdhali]

Thanks guys,
Just my hang up, but I seem to favour something solid over something wirey

 

[jassdhali]

Then again, working out the prices I will try the 200mm insulation roll

 

[jassdhali]

Hi,
Just about to tackle this now as I have a free few days.
Woody going off your suggestion picked up knauf loft roll at £3.00 at 200 mm thick. Thanks
I was wondering if there is any extra benefit in relation to keeping heat loss to a minimum if I were to double up the insulation so I have 400 mm in between the joists? Before being squashed obviuosly.
Also, would there be any issue in me using breathable roof membrane as the material to hold the insulation in place??

Thanks

 

[mointainwalker]

The extra benefit will be very very small. Not worth the effort IMO.

 

[stuart45]

Don't squash the insulation.

 

[dhutch]

Conderations as to airtightness and reducing drafts through the floor?

Ive yet to look under my floor but its on the list onf things to do, ive only recently moved in and currently the underfloor vents are blocked up from the outside. Just had the cavity and loft insulation done, so its airtightness and floors next. Hoping for not too much damp/rot!


Daniel