underfloor insulation - 3 scenarios - one house?
Discussion
I'm looking for ideas if anyone might spare the time?
The below is a floor plan of what I have. A very standard victorian (knock through) terrace and with stairs on the outer wall that rise to the landing and drop to the kitchen on the inner.
The pink is carpeted and the yellow and green are both stripped boards. The green and pink are suspended floors with about a 3 foot drop to the chalk floor but the yellow is about 5'7 and opened out into a cellar underneath. Again with a stripped floor above.
As you might expect the heat loss is abominable - but with three different factors I'm a little thrown.
Under the hall and lounge (pink and green) I am tempted to use 'loft roll' fastened into place with a chicken wire 'cage' between the joists - though am worried about fibres making it through the boards. This is in cheap preference to celotex which I have no experience in working with.
Under the yellow dining room where headroom is a factor I would go for full celotex to maintain some height and learn how to fix it properly.
As it stands there is no formal insulation between the boards (theres a century of grot which is largely plugging the gaps). I was planning on using Draughtex (a cylinder of foam) between them but it is quite apparent that, despite what my gcse physics teacher said, wood is actually not that great an insulator and heat loss would still be a factor even if this was done.
Am i overcomplicating things? should I just Draughtex the boards and accept thats a massive improvement and be done with it? Its been massively handy having access underneath for heating installation / CAT 5 / rewiring but this winter when the heating clicks off the temp drops like a stone which is not helping my wallet, my comfort or the environment. There are two operational fireplaces in the lounge / diner too which , when operational will just suck cold air up and, if anything may even make the rooms colder! (maybe - im not sure on that)
Id welcome any thoughts?
Edit - just to add - there is a crawlspace from yellow to pink and then to green currently. Id like to maintain this as it is not only very handy but also allows for air circulation between the suspended floor. in time id put a door with airflow in between the yellow dining room cellar and the pink hallway subfloor so this shouldnt have any impact.
The below is a floor plan of what I have. A very standard victorian (knock through) terrace and with stairs on the outer wall that rise to the landing and drop to the kitchen on the inner.
The pink is carpeted and the yellow and green are both stripped boards. The green and pink are suspended floors with about a 3 foot drop to the chalk floor but the yellow is about 5'7 and opened out into a cellar underneath. Again with a stripped floor above.
As you might expect the heat loss is abominable - but with three different factors I'm a little thrown.
Under the hall and lounge (pink and green) I am tempted to use 'loft roll' fastened into place with a chicken wire 'cage' between the joists - though am worried about fibres making it through the boards. This is in cheap preference to celotex which I have no experience in working with.
Under the yellow dining room where headroom is a factor I would go for full celotex to maintain some height and learn how to fix it properly.
As it stands there is no formal insulation between the boards (theres a century of grot which is largely plugging the gaps). I was planning on using Draughtex (a cylinder of foam) between them but it is quite apparent that, despite what my gcse physics teacher said, wood is actually not that great an insulator and heat loss would still be a factor even if this was done.
Am i overcomplicating things? should I just Draughtex the boards and accept thats a massive improvement and be done with it? Its been massively handy having access underneath for heating installation / CAT 5 / rewiring but this winter when the heating clicks off the temp drops like a stone which is not helping my wallet, my comfort or the environment. There are two operational fireplaces in the lounge / diner too which , when operational will just suck cold air up and, if anything may even make the rooms colder! (maybe - im not sure on that)
Id welcome any thoughts?
Edit - just to add - there is a crawlspace from yellow to pink and then to green currently. Id like to maintain this as it is not only very handy but also allows for air circulation between the suspended floor. in time id put a door with airflow in between the yellow dining room cellar and the pink hallway subfloor so this shouldnt have any impact.
Edited by paolow on Wednesday 10th January 19:39
Rosscow said:
So you’re looking to do all of this from below?
Yep - theres a good 3' of room (at the absolute shallowest) to get under there under pink hallway and green lounge. But not much leeway to move complete celotex boards hence my thoughts on those two sections using more flexible insulation.Indeed, it would certainly be easier stuffing earthwool type insulation and holding up with wire than trying to cut celotex inbetween the joists.
Alternatively you could fix 50mm celotex to the bottom edge of the joists? Overboard the entire lot. If you use the 450 x 1200 size it shouldn’t be too bad?
Once it was up tape the joints with foil tape to seal.
Alternatively you could fix 50mm celotex to the bottom edge of the joists? Overboard the entire lot. If you use the 450 x 1200 size it shouldn’t be too bad?
Once it was up tape the joints with foil tape to seal.
My concern with glass fibre type stuff wouldn't be fibres coming through the boards, it would just be that it's bloody unpleasant to handle and inhale. Fortunately you can get rolls of it encased in a sort of space blanket material so you're not exposed to the actual fibres: http://www.wickes.co.uk/Knauf-200mm-Space-Encapsul...
I believe you can also get natural fibres like sheep wool, etc
Might be worth investigating anyway.
I believe you can also get natural fibres like sheep wool, etc
Might be worth investigating anyway.
Edited by Risotto on Wednesday 10th January 22:27
Might be worth having a look at the various foil insulating blanket products out there.
I used some to do what you're planning but under the floor of a shed and it's very effective - not only adding insulation but, being completely airtight, it eliminates any draughts.
Installation would be easy - unroll then staple onto the bottom of the joists. Make sure there's a good overlap and then seal up the joins with foil tape.
I used some to do what you're planning but under the floor of a shed and it's very effective - not only adding insulation but, being completely airtight, it eliminates any draughts.
Installation would be easy - unroll then staple onto the bottom of the joists. Make sure there's a good overlap and then seal up the joins with foil tape.
I would be hesitant about tightly joint celotex preventing the house from 'breathing'. I don't know old places in detail, but my family does, and a big part of it is not sealing it up too tight.
I would go down the route of rockwool, with chicken wire holding it up & do that as much as you can. With a facemask, gloves & painters overall it is no issues at all working with. It will also be cheaper then celotex.
That will make a huge difference if you can fit in 200mm across everything, then maybe 100mm where height is an issue.
I would go down the route of rockwool, with chicken wire holding it up & do that as much as you can. With a facemask, gloves & painters overall it is no issues at all working with. It will also be cheaper then celotex.
That will make a huge difference if you can fit in 200mm across everything, then maybe 100mm where height is an issue.
Ive never done it, and understand my house has a much smaller crawl void, so currently rely on 3mm of foam underlay and the laminate flooring ontop, as installed by the previous owner. It does at least keep the drafts down by giving the floor reasonable airtightness, even if it does blow in under the skirting boards like a drain!
Insulation is good, but I agree that reducing the drafts at bay will likely be at least as important. No point in insulation if you are changing the air every 35 minutes! At which point you do then need to make sure you are not trapping moisture.
Sheeps wool sounds like a reasonable option, to reduce the amount of glass wool you get stuck in your skin eyes and nose. While still also being reasonable fire retardant.
Daniel
Insulation is good, but I agree that reducing the drafts at bay will likely be at least as important. No point in insulation if you are changing the air every 35 minutes! At which point you do then need to make sure you are not trapping moisture.
Sheeps wool sounds like a reasonable option, to reduce the amount of glass wool you get stuck in your skin eyes and nose. While still also being reasonable fire retardant.
Daniel
Edited by dhutch on Thursday 11th January 17:49
Risotto said:
My concern with glass fibre type stuff wouldn't be fibres coming through the boards, it would just be that it's bloody unpleasant to handle and inhale. Fortunately you can get rolls of it encased in a sort of space blanket material so you're not exposed to the actual fibres: http://www.wickes.co.uk/Knauf-200mm-Space-Encapsul...
I believe you can also get natural fibres like sheep wool, etc
Might be worth investigating anyway.
I did my camper van with recycled plastic bottle insulation which handles like Rockwool but is safe to breathe around and doesn't leave your arms looking like a smallpox victim's.I believe you can also get natural fibres like sheep wool, etc
Might be worth investigating anyway.
Edited by Risotto on Wednesday 10th January 22:27
Thanks for all the input everyone.
lots of food for thought - I hadnt considered sheeps wool insulation so am happy this is the way to go. For the 'in between' board insulation it was looking at £300 for the kit with me clearing the gaps with a padsaw - and sheeps wool has a massive advantage with the thermal coefficient and lack of fibreglass being in my floor.
Certainly under the hall and lounge anyway. The beauty is that cables / pipes etc are much easier to deal with when the insuation is more flexible to work with.
I'm still thinking on the subfloor in the cellar. I may yet go for some sort of foil solution - but a staple gun, chicken wire and sheeps wool is such an elegant solution I will probably do this here (albeit thinner and when I have had some pracctice on the other floors). I dont want to seal the whole floor with hardboard etc as I've read that condensation can occur as a resullt. Though Im happy enough that this will avoid any issues (hopefully)
It leaves the question as to what the hell to use the cellar for now that the house work is complete as its been my workshop. But i suppose thats a whole new thread. Mrs Paolow suggested I get back into brewing beer - which would be good - were it not for the fact that my previous efforts have been so rank...
lots of food for thought - I hadnt considered sheeps wool insulation so am happy this is the way to go. For the 'in between' board insulation it was looking at £300 for the kit with me clearing the gaps with a padsaw - and sheeps wool has a massive advantage with the thermal coefficient and lack of fibreglass being in my floor.
Certainly under the hall and lounge anyway. The beauty is that cables / pipes etc are much easier to deal with when the insuation is more flexible to work with.
I'm still thinking on the subfloor in the cellar. I may yet go for some sort of foil solution - but a staple gun, chicken wire and sheeps wool is such an elegant solution I will probably do this here (albeit thinner and when I have had some pracctice on the other floors). I dont want to seal the whole floor with hardboard etc as I've read that condensation can occur as a resullt. Though Im happy enough that this will avoid any issues (hopefully)
It leaves the question as to what the hell to use the cellar for now that the house work is complete as its been my workshop. But i suppose thats a whole new thread. Mrs Paolow suggested I get back into brewing beer - which would be good - were it not for the fact that my previous efforts have been so rank...
Just to add I am watching this thread with interest - currently no insulation under my house. - Which is a non-standard construction - concrete infill, so damp is something I have to avoid more than most.
Rockwool - really fire proof, not the easiest to get large amounts down through into the basement - I cannot get any larger myself or I wont get back out! Advantage in that it comes in bats that I could squeeze between the joists, but would still need supporting.
Sheepswool - really moisture helping, easy to get down into the basement, would be easy to stuff into more difficult to reach places, but would need supporting by chickenwire.
Kingspan (or any other brand) - impossible to get down, and near impossible to get a good tight fit between joists when crawling around in a 3 foot space with old bits of nails, screws and other detritus digging into your knees...
Foil blanket - I would say I would avoid due to moisture barrier, also cannot insulate across through the sleeper walls, but would avoid the thermal bridging of the above methods.
Do tell how you get on!
Rockwool - really fire proof, not the easiest to get large amounts down through into the basement - I cannot get any larger myself or I wont get back out! Advantage in that it comes in bats that I could squeeze between the joists, but would still need supporting.
Sheepswool - really moisture helping, easy to get down into the basement, would be easy to stuff into more difficult to reach places, but would need supporting by chickenwire.
Kingspan (or any other brand) - impossible to get down, and near impossible to get a good tight fit between joists when crawling around in a 3 foot space with old bits of nails, screws and other detritus digging into your knees...
Foil blanket - I would say I would avoid due to moisture barrier, also cannot insulate across through the sleeper walls, but would avoid the thermal bridging of the above methods.
Do tell how you get on!
I took up all the downstairs floorboards during renovations and insulated with Rockwool. A few things I learned from the experience...
1) You will find issues you hadn’t expected. Rotten joist ends, random (live!) wiring, fatigued/rusted nails, etc etc
2) Pulling up floorboards is a tricky job. I tried many techniques, bought a slide hammer type nail puller etc, but you will split the odd board.
3) My central heating pipes were uninsulated & hanging in the breeze on loops of copper wire nailed to the joists. I took the time to insulate them with the thickest insulation I could find.
4) Chicken wire was too awkward for me. In the end I found that thick weed protection fabric was a much more finger friendly substitute, but you may need to find creative solutions around the perimeter of the room.
5) Gold standard is to then seal with plastic sheeting, with the ends up against the wall, held by the skirting boards.
It really does make a difference, for me there was an opportunity to do it, but it’s a big old job. If you can do it from underneath then things should be a lot easier to do. Go for it!
1) You will find issues you hadn’t expected. Rotten joist ends, random (live!) wiring, fatigued/rusted nails, etc etc
2) Pulling up floorboards is a tricky job. I tried many techniques, bought a slide hammer type nail puller etc, but you will split the odd board.
3) My central heating pipes were uninsulated & hanging in the breeze on loops of copper wire nailed to the joists. I took the time to insulate them with the thickest insulation I could find.
4) Chicken wire was too awkward for me. In the end I found that thick weed protection fabric was a much more finger friendly substitute, but you may need to find creative solutions around the perimeter of the room.
5) Gold standard is to then seal with plastic sheeting, with the ends up against the wall, held by the skirting boards.
It really does make a difference, for me there was an opportunity to do it, but it’s a big old job. If you can do it from underneath then things should be a lot easier to do. Go for it!
Peanut Gallery said:
Sheepswool - really moisture helping, easy to get down into the basement, would be easy to stuff into more difficult to reach places, but would need supporting by chickenwire.
Organic Insulation can have issues, Sheepwool can attract moths so take care if exposed floorbpoardshttp://www.telegraph.co.uk/news/2017/09/01/grand-d...
Personally I wouldn't over think it, PIR insulation if warmth is most important, or mineral wool if accoustic also matters and perhaps a vapour barrier.
Just open windows around the house regularly, heating above dew point, use good quality bathroom & kitchen extractors, not dry clothes inside, keep air bricks free and other common sense stuf. Have some humidty sensors up and keep an eye on them and otherwise forget about it.
Yes these houses need to breathe, but also remember that when they were built the builders didn't have extractors/central heating/dehumidifiers and so on so the water vapour wasn't being extracted at whatever l/min modern extractors will do.
If floorboards are up, you could also brush the joists with some wood treatment.
Note: I have no training in this, DYOR and all that
Edited by hyphen on Tuesday 16th January 09:55
Unless you really love the floor boards it might be easier to surface mount. The enclosed pic is the hall way with a nuheat surface mount I installed 12 years ago. Total floor height goes up by about 1" but I guess you have plenty of head room in a Victorian house to spare. The house had been stripped in the 60s so nothing original left . You screw strips of OSB to the floor, put the heat spreader plates on top with the pipe then screw 12mm ply over the top if carpet or tile. No ply if engineered boards. 
Sorry don't know how to rotate that pic.
Sorry don't know how to rotate that pic.
Edited by mdw on Tuesday 16th January 12:31
if you do decide to use glasswool i would recommend using knauf loftroll its not itchy like the old glasswool and sheepswool is about 3 times as expensive, i would also use a breathable building paper to hold it up rather than chickenwire in the celler if you are going to be using that area
Don't know if you've seen the Canadian DIY series, Holmes on Homes? He's a great advocate of spray foam and I must say it does look the dog's danglies and would be my first choice
Have a look at this clip
https://www.youtube.com/watch?v=WpsQernFOvQ
No idea where you'd get it in UK though I bet there's contractors who will do it,
Yes, just Googled and here's one.
http://www.roofinginsulationservice.co.uk/?gclid=C...
Have a look at this clip
https://www.youtube.com/watch?v=WpsQernFOvQ
No idea where you'd get it in UK though I bet there's contractors who will do it,
Yes, just Googled and here's one.
http://www.roofinginsulationservice.co.uk/?gclid=C...
Thank you for the spray foam link, but..
Some have mega problems with the foam - https://www.youtube.com/watch?v=0Hh5MYv7lWc
(Yes, one off, American, early days of foam, things have improved since then)
I have also heard of 2 people in my office who have had this done, and the chances are that the wall air gap was closed in "to stop drafts" - hence they have now moved out and found a not so damp place to live.
Call me strange, but I prefer the idea of water being able to leak through the floor insulation and out - we have a 6 month old who can make enough splashes in the bath already to get the carpet outside the bathroom wet, (but it gets good giggles, and the tiles are easy to dry) so I am sure water will soak through everything, and out the bottom into the crawl space.
(Randomly, this bloke does a better, not speeded up version of explaining spray on insulation - https://www.youtube.com/watch?v=YMxq2HSIXjM
Some have mega problems with the foam - https://www.youtube.com/watch?v=0Hh5MYv7lWc
(Yes, one off, American, early days of foam, things have improved since then)
I have also heard of 2 people in my office who have had this done, and the chances are that the wall air gap was closed in "to stop drafts" - hence they have now moved out and found a not so damp place to live.
Call me strange, but I prefer the idea of water being able to leak through the floor insulation and out - we have a 6 month old who can make enough splashes in the bath already to get the carpet outside the bathroom wet, (but it gets good giggles, and the tiles are easy to dry) so I am sure water will soak through everything, and out the bottom into the crawl space.
(Randomly, this bloke does a better, not speeded up version of explaining spray on insulation - https://www.youtube.com/watch?v=YMxq2HSIXjM
I used this stuff in my loft recently
http://www.diy.com/departments/diall-loft-insulati...
It's more expensive than rockwool, but not that dissimilar in price to the encapsulated stuff and no issues with fibres
http://www.diy.com/departments/diall-loft-insulati...
It's more expensive than rockwool, but not that dissimilar in price to the encapsulated stuff and no issues with fibres
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