Spray Foam Insulation - for underfloor areas of the house

frozen_wastes

Hello,

I live in a 1993 detached bungalow. I'm looking to upgrade the insulation, and whilst I did a big effort upgrading the loft insulation nearly 10 years ago, the rest of the property is as per original building specifications.

My overall objective is to reduce consumption of heating fuels whilst maintaining or improving interior comfort. Currently I'm burning about 1400litres of LPG + 1.5tonnes of wood annually. I've noticed some draughts and cold floors near sink areas, so I plugged holes under sinks with expanding foam. However the cold floors and draughts are still present, so evidently I didn't do a good enough job.

Under the suspended chipboard joisted floor I've got fibreglass insulation held in place by suspended nets.

My thoughts are that since the underfloor area is accessible, it's also possible to upgrade. My preferred choice of material, PIR insulation board however is impossible to get through the floor hatches.

Multifoil insulation is also a No-No since that means covering the underside of the timberjoists leading to condensation and subsequent rot. I understand multifoils need to be slung over the joists, not under (meaning I'd have to lift the entire floor)

So I discovered spray foam insulation as an option. I have a local certified Icynene installer available, and they suggested using an open cell spray foam which is breathable.

The U Value is similar to fibreglass but it is apparently windproof and it gets into all nooks and crannies. Coverage of my underfloor fibreglass insulation is somewhat patchy by comparison.

So my question is whether anyone on this forum has retrofitted their house with icynene. My biggest concern is one of outgassing. I've read suggestions that if the two ingredients are not properly mixed then that can lead to nasty fumes that can be difficult to completely get rid of.

Any experiences good or bad would be interesting to read.

Doozergirl

No. No. No. Things do need to breathe down there and there's no option of removing that stuff, other than removing whatever it has stuck to. You can't maintain or alter anything if there is a problem and you may not even be able to see a problem occuring. I would never ever touch the stuff and I'd seriously re-consider buying a house where it had been used.

You're conscious of using other removable products because of the sensitive nature of timber, and yet considering smothering it permanently. It isn't logical.

If you already have insulation there, then maybe covering your floors again is an option. We have LVT flooring in our 1930s house and the upshot of putting 18mm ply over the entire ground floor is that it's sealed virtually all of the draughts coming up through the floorboards. The floor is noticeably warmer but we're not making any permanent changes to the subfloor which is still ventilated and actually not insulated either.

FreeBear

frozen_wastes wrote: »

So I discovered spray foam insulation as an option. I have a local certified Icynene installer available, and they suggested using an open cell spray foam which is breathable.

The installers and suppliers will make all sorts of claims about their products. Very few actually stand up to scrutiny. Breathability is one such claim - Ask (no, demand) to see an independent lab report that has been peer reviewed... Problem is, there is no widely accepted standard for testing for breathability, so they can make it up as they go along.

Also be aware of problems with sloppy installation - The main one is a fishy odour that lingers. Plenty of houses have been rendered uninhabitable by the smell in North America where they have been using this stuff for quite a few years.

One final word of warning - Should you ever come to sell the house, many surveyors will reduce their valuation considerably if they find spray foam insulation all over the place.

Grenage

Noooooooooooooooooooo.


We viewed a house once that had that stuff across the underside of the roof. I immediately crossed it off my list.

frozen_wastes

Thanks for your interesting thoughts on the matter. They are similar to the lingering doubt's that I've had. I've always considered that insulation retrofit work should be treated with utmost caution with respect to avoiding interstitial condensation.

Essentially it seems like suspended timber ground floors should be undercovered with no more than fibrous insulation (fibreglass, rockwool etc...). But at the same time I haven't quite accepted the fact that maybe my house cannot be insulated any further in an economic fashion.

Given my flooring is 22mm tongue and groove chipboard, the thermal performance should be similar to 18mm plywood. The problem I'm guessing will therefore be any penetration through the floor (pipes, drains and cables).

Pipework penetrations confronted me with quite large gaps where sinks were installed (holes looked like they were ripped open by the incredible hulk, rather than smooth circular holes made by a holesaw).

I attempted to seal up the holes under these sinks last summer, but I still get a draught coming from under the kitchen cabinets surrounding the sink.

Cable penetrations are everywhere in the floors or ceilings that I have a light switch or socket, but the holes are 22mm entries into a stud partition void. I did have a draught through one access hatch to a soil pipe buried in an internal wall, so I'm wandering if sealing these up will have any considerable benefit in terms of reducing inperceptible draughts.

Grenage

Yes, all the little draughts add up. Our house has no obvious gaps around the house, but one can feel an immense breeze coming through the living room door (and up the chimney).