Forum Topic

Under Floor Foam Spray Insulation

It was suggested to me that I have this done in my kitchen which is like Ice Station Zebra  in the winter.https://www.youtube.com/watch?v=OGahHbR8eSk&t=1sDoes anyone know anything about this or had it done?Is this foam toxic in any way and does it smell?Will it seal in any damp, prevent air circulation  and cause rot in the future?I would be grateful for any information or suggestions.Thank you.

Marlene Plimley ● 316d18 Comments

Marlene, I will give you the short version which is basically don’t use any spray insulation.10 years ago I did lots of research particularly as our houses are very prone to dry rot and need lots of underfloor ventilation.My solution was to clean out the underfloor and brick vents.  This left about a metre of space.  My regular team found a slim friend (he was a motor mechanic used to working on his back!). I bought 10cms Kingspan insulation and each slab was cut to the exact measurements of the joists.  This was pushed right against the floor boards from underneath and secured in place using long screws on either side at 1/3rd intervals.  At the end he wore goggles and a mask and sprayed expanding foam all round each piece.  We also found that none of the central heating pipes were insulated so they were done at the same time.This was not cheap but the difference in the warmth of the ground floor was massive and my carpets no longer ripple on windy days.  My heating bills were also greatly reduced.Have a look at UTube which is quite informative.  Any left over mater can be added to your loft but don’t push the slabs up to the tiles - you must have a ventilation gap - again UTube has good information.

Elizabeth Ross ● 315d

You may find this interesting:https://www.leti.uk/As I understand it the usual method for suspended wooden floors (common in this country) is to insulate between the joists.  The great fear is causing/allowing any condensation to form on wood causing rot. This is why there are air bricks to allow ventilation under the floor. With Passivhaus which is much talked about mechanical ventilation is used but when you build new rather than retrofitting you can easily seal the outside envelope of the building.More problems with condensation and mould are going to occur in homes if people do not use the bathroom and kitchen air extractors which are required under Building Regulations. Avoiding mould is a careful balance of ventilation and temperature control.  Drying washing indoors can be a big problem.This coming week there is a London Build Expo at Olympia and the following week a Homes UK event at the Excel for anyone who is interested.

Philippa Bond ● 315d

I think the rubber tubing floorboard draught excluder is called Draftex, which comes in a range of thicknesses for different width gaps.

Peter Evans ● 316d

It's explained here under mistake #1https://www.youtube.com/watch?v=zvL4va6P5F0

Bruce Hammal ● 316d

Correction- stopgap floorboard draught excluder

Jayne Thorburn ● 316d

Just googled answer came back ‘Stopgap floor draught extractor on Amazon’, good luck

Jayne Thorburn ● 316d

I see it is mentioned on the Energy Saving Trust website but it is new to us.  I also notice that the roof insulation which we know has caused so many problems appears to have been caused by the wrong foam being used.  How do you tell what is the right or wrong type?

Philippa Bond ● 316d

We had the gaps between our floorboards filled by a company that pushed/hammered in different diameters of black rubber tubing. They stopped the draughts and aren't noticeable from above. The previous solution was to put carpet down.

Peter Evans ● 316d

There are several low-tech products designed to address the floorboard draught issue. I used one in my last house and it seemed reasonably effective.If nothing else I’d be worried that this foam stuff would force its way up through the gaps and leave the floor looking a mess.

Bruce Hammal ● 316d

Thank you everyone for your comments and tips and I did listen to Moneybox. What a coincidence it was on today!So, I think I've made a decision not to have this done.I've never been a fan of chemicals and who knows spray foam may in future become an environmental and fire hazard and very hard and £££ to remove.

Marlene Plimley ● 316d

My floor is plain old pine floorboards on joists with gaps between them from shrinkage.

Marlene Plimley ● 316d

What is the construction of your floor?

david ward ● 316d

I would only be doing this if it could be proven that the gaps in the floor were the source of the majority of the chilling effect.  But then I'd still have loads of questions.If it was my place I would do a temporary solution for at least a month that cost pittance and could be put down or removed in an afternoon.  I've just spent 2 hrs 3 days ago finding the weak points in the seals in my double sized upvc front doors.  I had to wait until its at least somewhat windy from the right direction then use a joss stick for the white smoke and a led torch to reflect off the smoke particles and you can see  where it gets turbulence very easily.  Fixing them is another matter.  If it were me I would find the large obv gaps in the floor and do a temp solution (even if it's just tape) for a month to prove what affect if any it might have. There are draft tapes of various profiles and thicknesses that could be put in easily without fixings, then go from there.

Andrew Craig ● 316d

It also worries me that there is flammable insulation being advertised without enough (or any) warnings about its flammability.  Just looking at the pictures you would think it is a doddle to fit...  but you need to investigate further.This is particularly worrying when many people are thinking about using or are using open fires as well as central heating.

Philippa Bond ● 316d

I've never come across an underfloor version of this but it seems to be a very  similar process to that which used to be heavily advertised for use on roof tiles. Supposedly it would solve leaks and stop slipping tiles while providing extra insulation. Unfortunately there's no cheap and easy solution to a worn-out roof so all it did was delay the inevitable and put off potential buyers as it provided clear evidence that there was a problem with the roof!

Bruce Hammal ● 316d

I heard all of the report on Money Box. One woman had to pay thousands to get the foam removed before she could sell her house.Check it out on BBC Sounds.

Susan Kelly ● 316d

Be very careful - that isn't the only 'solution' being offered online which may not be all that it is cracked up to be.  Some of these things can look an easy solution but there isn't enough technical info on what it is, where, on what surface and how and how not install it etc.  You are right to be cautious and investigate.This is one of the reasons why with our old and very leaky homes we are still not as well insulated as other countries.  Another is that when the Govt did have initiatives to help us there weren't enough people trained and able to carry them out.

Philippa Bond ● 316d

The Money Programme on Radio 4 have just featured a piece on spray foam insulation you might like to listen to that on BBC Sounds. The bottom line is get expert advice don't rely on the companies who do the work as spray foam may affect mortgages and house insurance.  (I only heard the end of this  section.)

Helen Whitman ● 316d