I've a rather old n draughty cottage.
Lofts boarded and has rock wool I've mentioned insulation before I was wondering if there's a downside to spray foam insulation. Looks fast easy and effective. Which makes me kind of Concerned as it looks to good to be true.
Any experience of it?
I don't know, but my initial thought is: if it's that good why isn't everybody using it? 🤔
Foam in the form of kingspan/celotex is more efficient in terms of thickness than rockwool.
But that is produced in carefully controlled conditions unlike spray foam which is probably a two pack mixture squirted out under pressure in your loft.
I'm not sure that you can draw any comparisons between the two!
I'd be VERY wary. There's real risk that with no air-flow condensation will form on your roof timbers leading to rot, and needing a complete new roof.
There's no way I'd even consider any property with this done (former building surveyor).
APF
https://www.which.co.uk/reviews/insulation/article/spray-foam-insulation-ajTlp7t5K7lT
Might be useful for you.
In regards to rot, there is a guy renovating a 1930s house on YT called Gosforth Handyman - brilliant channel (not affiliated in any way just like his stuff and fascinated by process etc) - that house had the spray foam and in one of the episodes he had to cut roof timbers and they were in perfect condition. Might also be worth a watch. Sorry cant remember which episode!
I have used zillions of cans of spray foam to insulate and draft proof my attic. Its mainly insulated with kingspan / celotex but spray foam in strategic places has reduced drafts a lot. the danger is you end up with condensation
Single shot Spray foam in a can is not the stuff you want in a roof space.
You want open cell breathable most likely for what you are doing. $$$$$
Don't use closed cell gap filler as insulation against timber
No it’s bad. I can’t remember why.
As its on the timber like a coating I wouldn't think condensation was an issue...
https://www.abbuildingproducts.co.uk/touch-n-foam-200-spray-foam-kit.html
I know it's used in marine
I'll probably celotex the ceiling when I drop and replaster board but was just looking at improving the draught protection as that just pulls heat out.
It's a huge area of contention, in the USA on timber frame houses it's used loads essential craftsman used it on his spec house build if you like the Gosforth Handyman YouTube channel the essential craftsman is also fantastic. He covers spray foam in an episode.
It's not something I would haves used when I was in the building trade. But things change I guess.
I would ring your lender too and ask their opinion if you have one.
Skillbuilder covered it recently.
I like the idea of it in new timberframe but not in potentially leaky and rotting old roofs.
I'd be very very careful, can cause huge technical problems on an old house, there are other methods but more intrusive/labour intensive. Old houses need to breath. We/I always advise against this form of insulation! Also many lenders will not mortgage.
Qualified to comment too being Architects and Passive House designers who work on old buildings a lot.
Also many lenders will not mortgage.
When does a mortgage company inspect your attic?
Remortgage for value? Or if you want sell up. Some lenders don't like it
isocyanate based, bloody harmful stuff as its gassing off (respiratory sensitiser) if there was ever a fire then mega toxic thermal decomposition.
I would avoid it like the plague.
I keep getting adverts for this type of insulation in my Instagram feed.
Apparently you can get a grant towards the cost of it as well.
Just be careful where you apply it
Building surveyor, I wouldn't use it. Aside from the issues around condensation which could be severe, there are health issues and fire issues associated with it. Granted it's going in a roof space but the potential is there for it to affect the habitable space. Unlike closed cell insulation boards which are a similar material, the spray on site stuff will be undergoing heavy offgassing and curing for long periods of time within the house whereas rigid boards have already undergone the majority of that process at the factory and in storage.
Cheers chaps, just looked interesting but I wasn't fully sold!
Celotex it is.
and fire issues associated with it
Can't be worse than standard Celotex etc which give off Hydrogen cyanide when burnt...
Just to add to the canned foam comments, from my understanding, canned foam is open cell, not flame retardant, and absorbs moisture. 2 part spray foam with cylinders and an applicator gun is closed cell, somewhat fire retardant and does not absorb moisture.
bought a house with it in 2012, was unable to sell that house in 2019, had to submit 3/4 quotes for removal, buyers bank wouldn't lend based on the insulation/potential rot to timbers, (2 of the bedrooms suffered with ridiculous amounts of damp, may have been related?) money was held in retention and it all had to be removed post sale, which it was, but had to knock the cost of the cheapest quote off the price, had so many builders come and look and just go, nah, no chance, that's a ball ache of a job
Retrofitting to the underside of an already finished roof designed for airflow? No.
New install on a the underside of an unvented plywood roof deck with a fully adhered butyl/asphaltic membrane over top of the deck creating a homogenous "single layer"? yes.
Diy kits? Nope.
https://www.edu-chem.co.uk/ Ring Deb tell her Steve at Crowfoots pointed you here she will explain all the details and best options
footflaps celotex is also isocyanate foam, just blown into sheets rather than left to expand openly. they all produce cyanides an other jollies on ignition.
my father was one of the team of polymer chemists that first developed the foams for use in north sea pipeline insulation. He bloody hates the stuff
footflaps celotex is also isocyanate foam, just blown into sheets rather than left to expand openly. they all produce cyanides an other jollies on ignition.
Was thinking about that as I installed 65 sheets in the workshop. If it ever catches fire, I don't want to be anywhere near it!
isocyanate based, bloody harmful stuff as its gassing off (respiratory sensitiser) if there was ever a fire then mega toxic thermal decomposition.
I would avoid it like the plague.
The foam is based on MDI isocyanate which has a low vapour threshold. The isocyanate is fully reacted in the mixing chamber in the applying process, the 'gas' produced is mainly water vapour with very small amounts of amine and tin salt catalysts.
In case of a fire it decomposes exactly the same as the large amounts of PU also in the house (sofa, upholstery, mattress, carpet backings etc) see also Kingspan rigid PU insulation.
The 'chemistry' contents of spray foam wouldn't stop me from professionally applying it in a house but I wouldn't apply it to an old house due to the condensation issues mentioned above.
The foam is based on MDI isocyanate which has a low vapour threshold. The isocyanate is fully reacted in the mixing chamber in the applying process, the ‘gas’ produced is mainly water vapour with very small amounts of amine and tin salt catalysts
its not all fully reacted at mixing as you also get the diisocyanate pre polymers and monomers hence the reason why we monitor personal exposures under COSHH and users undergo biological monitoring and use positive pressure RPE (usually air lines, in industrial settings)
also depends on what blowing agent is used within the mix. once its all cured then its inert
