Suspended Wooden Floor Insulation - Mineral Wool or SuperQuilt?

[Martin Quinn]

I am looking to insulate my front room via the crawl space under the suspended wooden floor.

I am torn between using standard loft insulation, or SuperQuilt. I see the SuperQuilt as being the easier install, but I am not sure on which would provide the best insulation.

As the width between the joists is only 28cm I would have to cut the wool several times per roll, where as I think the SuperQuilt can just be stapled straight across the joists?

This image is from the SuperQuilt website;

Any advice or tips would be appreciated.

 

[geraldthehamster]

Celotex

 

[Martin Quinn]

I would have to lift the floorboards to use this due to the opening and depth for getting in the crawl space.

 

[Mr Chibs]

SuperQuilt it is then.

Are you sure you can't do foam boards from the crawl space?

 

[Martin Quinn]

If I cut it in 120cm lengths and it flex'd a little then maybe, but it seems quite a bit more expensive so it would need to be much better than the other options.

I have since read that SuperQuilt and other foil options are over rated and not as good as some of the accreditation's suggest?

 

[Mr Chibs]

Also, foam boards are twice as good as rockwool.

Foam will be a better job, you could stuff it up, under the floorboards, hold it with a nail and foam any gaps and tape if you want to go the whole nine yards.

 

[Martin Quinn]

So if I went with board, does it need to be 100mm and above to get any real benefit? Then simply cut the board to size maybe leaving a few mm extra so it fits tight, hold it up with some galvanized nails and then foam and tape as required?

Do you push the board up tight to the floorboards or leave a gap?

 

[Mr Chibs]

I suppose the thicker the better, but there will be a law of diminishing returns.
I'd suggest minimum of 50, 100mm better... I'm sure others will add their views.

You might be able to buy seconds... depending on where you live, for delivery etc.

Yes, tight to the underside of the floorboards, no gap needed.

I'd try for foil faced,... but if not possible, it won't be the end of the world.

 

[Martin Quinn]

Ok thanks.

I will have a look online and see what I can get. Going to aim for at least 100mm, got to be better than letting the cold air in without restriction as it is now.

 

[geraldthehamster]

50mm is fine. 100mm obviously better but you aren't losing a lot of heat through the floor anyway. It's mainly about eliminating draughts and making it warmer under foot. Depends how much you want to spend.

You might find it easier to get rock wool under there if access is restricted.