Insulation for suspended wooden floor
Discussion
I'm just about to rip up a chipboard floor and replace with reclaimed floorboards. While I'm doing this I thought that it might be a good idea to add some insulation as the idea is to have a waxed wooden floor without carpets. It's a downstairs room in an old Victorian house with solid walls.
Is insulating between the joists worthwhile? What should I be using - Celotex between the joists or some sort of netting and loose fill insulation?
Is insulating between the joists worthwhile? What should I be using - Celotex between the joists or some sort of netting and loose fill insulation?
You maybe limited on space if the floor joists are supported by sleeper walls as they maybe only 75 or 100mm deep.
Personally, I would use a rigid board, like Celotex. There are plenty available to choose from. Also, you can buy 'seconds' that may have damaged edges or poorly attached foil facings. E-bay search or Gumtree may well reveal a local source. Howarth timber are currently doing Ecotherm boards at a discounted rate.
Buy a proper insulation saw for cutting them - Toolstation do the Celotex one for £10 - they work significantly better than a knife or normal saw.
Also buy 100mm wide aluminum tape to seal the joints between the boards and timbers. If you fully fill between the joists (so the tops are flush) then this is easy.
If you cut the insulation properly then it should stay 'wedged' between the joists. If not you can half hammer in a nail every 200mm then set the boards onto them. The tape will also hold it up.
If the joists are deep enough then fit 120mm thick boards. This surpasses the Building Regs minimum.
Where you have pipes or cable runs then lay the insulation below them. Any pipe runs below the insulation will need to be insulated using Water Byelaw compliant pipe insulation.
Mineral wool insualtion on netting would be easier. However, it will allow air to permiate and as you said you want to have bare floor boards this will compromise it's efficency as the air will pass the joints in the boards. And you'll need a deeper layer of mineral wool.
Personally, I would use a rigid board, like Celotex. There are plenty available to choose from. Also, you can buy 'seconds' that may have damaged edges or poorly attached foil facings. E-bay search or Gumtree may well reveal a local source. Howarth timber are currently doing Ecotherm boards at a discounted rate.
Buy a proper insulation saw for cutting them - Toolstation do the Celotex one for £10 - they work significantly better than a knife or normal saw.
Also buy 100mm wide aluminum tape to seal the joints between the boards and timbers. If you fully fill between the joists (so the tops are flush) then this is easy.
If you cut the insulation properly then it should stay 'wedged' between the joists. If not you can half hammer in a nail every 200mm then set the boards onto them. The tape will also hold it up.
If the joists are deep enough then fit 120mm thick boards. This surpasses the Building Regs minimum.
Where you have pipes or cable runs then lay the insulation below them. Any pipe runs below the insulation will need to be insulated using Water Byelaw compliant pipe insulation.
Mineral wool insualtion on netting would be easier. However, it will allow air to permiate and as you said you want to have bare floor boards this will compromise it's efficency as the air will pass the joints in the boards. And you'll need a deeper layer of mineral wool.
I have just completed the same job on a 10m x 5m room. As we have not replaced the floor I had to cut holes in the floor and crawl around in the void underneath.
Without a doubt it was the worse thing I have ever done in my life! No doubt if you are taking up the floor it will be a darn sight easier though.
I used netting and standard glass fiber wool insulation. I took temp readings before and after and found no difference in temperatures. Plus the house does not feel warmer either, some folks have said it makes an amazing improvement I haven't found any to be honest.
Don't think you need building regs to insulate your floor but I could be wrong.
Without a doubt it was the worse thing I have ever done in my life! No doubt if you are taking up the floor it will be a darn sight easier though.
I used netting and standard glass fiber wool insulation. I took temp readings before and after and found no difference in temperatures. Plus the house does not feel warmer either, some folks have said it makes an amazing improvement I haven't found any to be honest.
Don't think you need building regs to insulate your floor but I could be wrong.
I'm surprised no one has mentioned ventilation... This doesn't seem like a good idea to me. You need to do some proper investigation. If the house has stood for 100+ years, you will be compromising it's integrity. Typically a Victorian house will have a ventilated floor, to take away moisture, you will be impeding this by filling with insulation.
cuneus said:
mk1fan said:
If the joists are deep enough then fit 120mm thick boards.
How much can you get these for?I looked on the bay and they are about £45 EACH!!!!
170mm "wool" is about £3 for comparison
I need 28m2 for the floor, and 28m2 for the roof! £800+ on insulation that I thought would be half that!
Celotex/Kingspan etc is designed to retain heat, not sound, the same applies with the sort of mineral wool insulation some are talking about in here.
You can buy acoustic partition roll or better still in your case a Rockwool product called RWA45 in various thickness's, including 100mm for under £20 + vat for a 2.8m2 pack. It can be cut to size to friction fit between the joists & still leave an air flow if required.
Drop me a private mail if I can help. (see the link on my profile for more info)
Nick
You can buy acoustic partition roll or better still in your case a Rockwool product called RWA45 in various thickness's, including 100mm for under £20 + vat for a 2.8m2 pack. It can be cut to size to friction fit between the joists & still leave an air flow if required.
Drop me a private mail if I can help. (see the link on my profile for more info)
Nick
So, do you need building regs for that sort of thing?
I'm planning to do it next summer along with drylining the whole house (does *that* need regs approval?), plus replacing heating and rewiring. Fun times ahead!
Anyway, does anyone know what does and doesn't require approval? I would have thought approval would not be a problem even when drylining an existing cavity wall (either a composite board with plaster dabs or, more likely, framing with foil-backed celotex and all joints taped with the celotex foil tape). I hope I'm not wrong.
I'm planning to do it next summer along with drylining the whole house (does *that* need regs approval?), plus replacing heating and rewiring. Fun times ahead!
Anyway, does anyone know what does and doesn't require approval? I would have thought approval would not be a problem even when drylining an existing cavity wall (either a composite board with plaster dabs or, more likely, framing with foil-backed celotex and all joints taped with the celotex foil tape). I hope I'm not wrong.
We fitted insulation between the floor joists of our Victorian terrace when we replaced the floors. Closed cell insulation, fitted tight between the boards onto screws fixed at an appropriate depth. Then taped the top surface.
Made a huge difference to the heating bills. Turned our boiler down from 6 to 1 last winter.
Whilst the floor is up, insulate any heating pipes and check the air bricks are clear. We also removed a fair bit of debris from under the floor.
Made a huge difference to the heating bills. Turned our boiler down from 6 to 1 last winter.
Whilst the floor is up, insulate any heating pipes and check the air bricks are clear. We also removed a fair bit of debris from under the floor.
eps said:
I'm surprised no one has mentioned ventilation... This doesn't seem like a good idea to me. You need to do some proper investigation. If the house has stood for 100+ years, you will be compromising it's integrity. Typically a Victorian house will have a ventilated floor, to take away moisture, you will be impeding this by filling with insulation.
I think this is a point well made. A structural engineer said to me years ago when we were refurbing a Victorian House with galloping dry rot ' You never see dry rot in a barn. Its because they are so well ventilated, no pools of still air.'
He was substantially correct: ventilation is the lifeblood of preserving timber in floors.
If you affect this in any way you need to be aware that you could be inviting trouble.
If you can still ensure truly adequate ventilation fair enough. Good Luck.
cuneus said:
I asked about 120mm boards.
How does wool work in a loft ?
I know. I just happened to buy a sheet of 100mm at the w/e so knew the price.How does wool work in a loft ?
Wool works in the loft because the plasterboard / lathe and plaster is a closed surface. Unlike floorboards that have gaps between them [that open and close].
If you were to lay wool over just lathes then it wouldn't work as well.
Edited by mk1fan on Thursday 3rd November 19:07
dxg said:
So, do you need building regs for that sort of thing?
I'm planning to do it next summer along with drylining the whole house (does *that* need regs approval?), plus replacing heating and rewiring. Fun times ahead!
Anyway, does anyone know what does and doesn't require approval? I would have thought approval would not be a problem even when drylining an existing cavity wall (either a composite board with plaster dabs or, more likely, framing with foil-backed celotex and all joints taped with the celotex foil tape). I hope I'm not wrong.
Asked and answered already.I'm planning to do it next summer along with drylining the whole house (does *that* need regs approval?), plus replacing heating and rewiring. Fun times ahead!
Anyway, does anyone know what does and doesn't require approval? I would have thought approval would not be a problem even when drylining an existing cavity wall (either a composite board with plaster dabs or, more likely, framing with foil-backed celotex and all joints taped with the celotex foil tape). I hope I'm not wrong.
If you're going to be drylining the whole house then save time and effort of framing and use a laminated plasterboard dot and dabed to the wall. The better performance versions act as vapour barriers too.
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