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We have a crawl space underneath our house, and wooden floor on top of floorboards on the ground floor. Is it worth putting insulation underneath the floorboards? Heat rises so is there any point?
If I use rockwool should I use netting to hold it in place?
TIA
If I can share my experience, we have a suspended timber floor and I installed some insulation in-between from underneath. I used wooden battens to hold it in place, drilling the batten into the underside of the joist. Definitely made the floor feel warmer.
We've just had a load of foam - technical term - splurged between the floor joists in our front room. Special foam mixed up in a van outside then applied with some sort of giant vacuum cleaner.
Too early to tell what difference it's made, but the floor in our front room's always been freezing cold to touch in winter - same scenario as the OP, plank flooring over original floorboards over a crawlspace. Floor currently feeling pleasantly warm.
As rockwool is cheap, but horrible to work with in such a space it’s got to be worth a try
90mm kingspan between the joists made a massive differance in our house. had to take up the floorboards to fit it though but needed to to get the UFH pipes and bisciut screed in(that was why i used 90mm as needed to leave 25/30mm for pipes and screed.
UFH isn't connected up yet but last winter the room was much warmer/retained the heat from the log burner much better.
As rockwool is cheap,
Works best with a membrane of some sort - like pertex over a fleece jacket. So wedge the insulation in between the joist but then trap them in place with a membrane - stops it falling out again but also improves the perfornance of the insulation
horrible to work with in such a space
Just bought a place with a similar crawl space under - haven't moved in yet (got two months notice to give on my current place) so giving it a good old strip and redecoration while its nice and empty - theres only about 2 feet of the space under the flioor and I'm 6'6" and the ground under is strewn with rubble so pretty uncomfortable. I think the quickest way is just to lift the floor boards, insulate and refit them. Doing it that way you fit the membrane first across the bottoms of the joists then sit the insulation in then board back over.
Agree, unfortunately that would mean lifting the engineered flooring, underlay and then the floorboards. Just going to have to get dirty and a sore back crawling around underneath. Would roofing membrane be appropriate?
Would roofing membrane be appropriate?
Couldn't tell you - I only poked my head through the floor yesterday so haven't made a shopping list yet 🙂
I’m lining up the exact same job. Going to be misery, 2ft crawl space and full of debris. Annoyingly, we’ve got concrete beams and wooden boards - so I can’t staple to the beams. Going to use some of that foil bubble wrap stuff and staple to the boards and pass over the beams before stapling to boards again. Not ideal - but I can’t think of a better option. Open to alternative ideas!
I used the pre-bagged rolls of insulation. Crawled into void and wedged insulation between joists from beneath. Then stapled it into place.
Horrible, horrible job with full PPE.
I need to do the living room now but looking at a 40mm multi foil. Will staple it to the bottom of the joists to create seal. I now get a discount through work and really not looking forward to it..
We’ve just had a load of foam – technical term – splurged between the floor joists in our front room
How does that work, do they just fill up the entire void? I have an 18"-24" void, I'm not claustrophobic but I've decided there is not enough space for me do actually be able to do any thing if I could squeeze under there!
No, it's viscous enough to just form a thick layer under the boards / between the joists then set hard. The guys who did it were based in Marple:
https://greenhorizonenergy.co.uk/spray-foam-insulation/
It's obviously much cheaper and 'more satisfying' to do it yourself, but this was pretty much hassle free and took around four hours from start to finish. All we had to do was crack open the hatch to give access to the crawlspace and give them money. From memory they need around two foot of vertical space under the floor, though don't quote me on that.
I used the pre-bagged rolls of insulation. Crawled into void and wedged insulation between joists from beneath. Then stapled it into place.
That's exactly what I did. Well I've done the bit where a I can almost stand up, I need to do the rest which won't be much fun.
My top tip is to cut the rolls to width, slightly wider than the gap between the joists (an old panel saw worked fine), whilst it's still rolled up. Then begins the game of shoving it in place and trying to staple the nets in fast enough before it all falls out again. All whilst crouching / lying on your back in the debris under the house.
Only managed half a room so far. A fun autumn to come!
Didn't use kingspan type foam as I understand that it needs to be pushed right up to the boards and sealed to prevent condensation. Rockwool should allow airflow to keep everything dry.
I might fit a membrane later on or in other rooms. When I looked it isn't roofing membrane which is normally waterproof an breathable but Tyvek breathable membrane which is breathable and not waterproof. I may have this wrong and it's just marketing BS.