Suspended Floor Insulation

[Jordan MacGregor]

Hi,

I'm looking to insulate the suspended floor at ground level. There is a 3ft void underneath the floor. I've been looking at using this stuff,

https://ybsinsulation.com/floor-insulation/suspended-timber/superquilt-suspended-timber/

I would be installing as show in the attached picture.

Is it worthwhile or a waste of time/cash?

Would i just be better off using PIR or Fibre Roll. The main 'put-offs' from those options are cost, and i reckon it wouldn't be a pleasant job installing from underneath.

Cheers in advance.

 

[^woody^]

This type of institution generally has to be used in combination with some other type of institution to meet the certification for building control.

I see there is no certification anyway for use in floors.

It must be installed in accordance with the manufacturer's instructions, your image does not appear to be.

I'd suggest that this product is not as good as claimed, and other more traditional insulation types would actually perform better.

 

[Jordan MacGregor]

It must be installed in accordance with the manufacturer's instructions, your image does not appear to be.

That image is from the manufacturers installation instruction, for that product, for a suspended floor with a crawl space.

There is certification for use in floors, but to meet building regulations, to be used with additional insulation. That (to me anyway) doesn’t mean it wouldn’t still be beneficial.

 

[^woody^]

There is certification for use in floors, but to meet building regulations, to be used with additional insulation. That (to me anyway) doesn’t mean it wouldn’t still be beneficial.

Beneficial? The issue is by how much and at what cost?

Whilst there might be a diagram, there does not appear to be certification for use in a floor. If so then it's not been tested to a standard.

These foils have a bad reputation in the industry. They are only pushed by the manufacturers

 

[Jordan MacGregor]

These foils have a bad reputation in the industry. They are only pushed by the manufacturers

Fair enough, hence my query on here.

My use for it doesn’t amount to much more than being a draft excluder, which would be fine as the thinner stuff (than quoted above) is relatively inexpensive.

 

[^woody^]

For draught exclusion joints will need to be taped and the perimeter sealed. And the joists will need sealing into the wall.

 

[endecotp]

Why not just use mineral wool?

 

[Jordan MacGregor]

Why not just use mineral wool?

Yeah - i’ve thought about it. Just thought stapling the other stuff was easier than trying to secure the wool from underneath the floor.

Open to suggestions on how to secure the wool from underneath...

 

[Jordan MacGregor]

Thinking of going for this stuff, just not sure of the best way to secure it to the underside of the floor?

100mm Knauf earthwool dritherm cavity slab

 

[JohnD]

mineral wool can be stuffed tightly between the joists, and, at the edges of the room, against the wall, which blocks the draughts. Draughts are worst around the edges, where they come up under the skirting gap. You must not block airbricks (clean them out)or subfloor airflow in the void.

usually the wool is supported by stapling garden netting or similar to the joists first.

Rigid foam has to be a precise fit to prevent draughts, usually achieved with individual cutting, and expanding foam for irregularities. It is not pleasant if it catches fire.

I don't know how you'd block draughts at the room edges with the foil products.

If the floor is being lifted for some reason, it is especially easy to lay insulation, but you can do it from underneath.

I only use the Knauf-made mineral wool, which is treated with Ecose to prevent irritant dust and fibres. It is also sold as an own-brand but you will see "Ecose" badged on the wrapper. It is brown, not yellow. I find yellow fibreglass very bad.

Loft rolls are usually cheaper to buy than cavity slabs, and the price is reduced for clearance as soon as the cold weather ends.

Sold in every DIY shed and builders merchant in the land.

 

[Notch7]

Thinking of going for this stuff, just not sure of the best way to secure it to the underside of the floor?

100mm Knauf earthwool dritherm cavity slab

if you dont mind spending more for less aggro how about actis hybris insulation -you cut it rolled up then stuff it in place.

I wouldnt want to be fitting knauf earthwool in a crawl space and having to look upwards whilst doing it.

PIR would be a nightmare working below -easy if from above

 

[Jordan MacGregor]

mineral wool can be stuffed tightly between the joists, and, at the edges of the room, against the wall, which blocks the draughts. Draughts are worst around the edges, where they come up under the skirting gap. You must not block airbricks (clean them out)or subfloor airflow in the void.

usually the wool is supported by stapling garden netting or similar to the joists first.

If the floor is being lifted for some reason...

Perfect, thanks for the advice. Airbricks are clear, and the netting sounds like the best option.

 

[endecotp]

Get a mineral wool product that is "nice to handle" (there is a trade name "Ecosse"). Wear a mask (!!).
Fix with chicken wire, or bailer twine, or barrier fencing, or almost anything else stapled to the bottom of the joists. (It will hold itself in quite well while your sort out the support.)
With a three-foot crawl space it won't be difficult; people have posted pictures of working in much smaller spaces.
If there are pipes, make sure they are insulated. If there are electrical cables, make sure they are NOT insulated.
"Actis Hybris" seems to be another "multifoil" product; I'd avoid it.

 

[Jordan MacGregor]

Get a mineral wool product that is "nice to handle" (there is a trade name "Ecosse"). Wear a mask (!!).
Fix with chicken wire, or bailer twine, or barrier fencing, or almost anything else stapled to the bottom of the joists. (It will hold itself in quite well while your sort out the support.)
With a three-foot crawl space it won't be difficult; people have posted pictures of working in much smaller spaces.
If there are pipes, make sure they are insulated. If there are electrical cables, make sure they are NOT insulated.
"Actis Hybris" seems to be another "multifoil" product; I'd avoid it.

Cheers! The pipework is insulated, done that when i was upgrading the pipework of the CH system and changing radiators, already had adventures under that floor