Spray Foam Insulation within Roofs

Does it work?


Spray foam insulation and what do Surveyors think

foam insulationWe can provide help and advice with regard to structural defects reports for things like problems with your roof, insulation, window problems, dampness, lateral dampness, condensation, cracking, movement. We carry out building surveys, structural surveys, property surveys, structural reports, engineers reports, home buyers reports or any other property matters.

As you can see from this article we photographs and also easy to understand sketches in all our survey reports, as the feedback we have from our clients is that the sketches and photos help them understand the reports.

We, of course, like to meet you at the property during the survey and we are more than happy to talk to you about the reports. Please free phone 0800 298 5424 for a friendly chat with one of our surveyors.

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Spray foam insulation, has it ruined the house?

foam insulationWe looked at a lovely house today where the people were obviously very house proud. The general care that they had taken in looking after the building was evident throughout, until we extended our ladder up into the loft space (we have one of these extendable ladders that can get almost anywhere which was a fantastic invention).

The building survey/structural survey was going so well up to this point when we saw within the roof that spray foam insulation had been used.

Spray Foam not recommended by most Surveyors

As we entered the roof we could see that the whole of the underside of the roof had been sprayed with spray foam insulation. If you haven't seen this before spray foam insulation is frequently advertised in newspapers and magazines and all over the internet. It looks a bit like a Crunchie bar without the chocolate or if you are a keen DIYer its very much like the expanding foam that you use to fill in gaps that's available from B&Q, Wickes or other similar good DIY places, that you spray in to fill any gaps or holes that you have when you have carried out work.

foam insulation

Spray foam, a close up

foam insulation

General view of roof with spray foam everywhere

Spray foam the benefits?

If you read the sales literature from the various spray foam companies they will say spray foam is used for several reasons:

1 The spray on foam salesman's pitch goes something along the lines of that the spray foam stops tiles and slates from slipping and strengthens the roof by holding them in place.

2 Increases the insulation in a roof and protects water tanks and pipes from freezing.

3 It creates a dry, clean, useful loft space.

4 We have heard it claimed to be environmentally friendly.

5 It's quick

We think that these above claims are debatable at best and probably the last claim that it is quick, is a reason why most people use it as they have a fear with a roof leaking or in bad condition that it can;

1 fall off and injure people coming by or fall in and injure them

2 that the roof will leak and damage all of their goods inside

There are lots of manufacturers who deal with the selling of spray foam. If you Google spray foam insulation for houses on the internet you will come across the following companies:




Spray Insulation Ltd

Foam Insulation

Isothane Ltd

As well as a number of DIY sites.

So what is the spray foam?

The spray on foam is a rigid foam that is lightweight, normally sprayed on to the underside of the roof approximately 50 to 100 mm thickness.

1 Some manufacturers advise that the spray foam is breathable, some of them say nothing at all about this.

2 Many say it has a British Board of Agrement or BBA approval which means the same thing.

3 Some give guarantees for 25 years or so.

Everyone in the spray foam industry seems to be pushing the benefits of spray foam, however why do many independent surveyors still not like it or recommend it and many surveyors who are valuers will down value a property because it has the insulation.

We have heard that also the National Federation of Roofing Contractors doesn't recommend it. It could be argued that the National Federation of Roofing Contractors are losing out with this technology as it is a competing technology they are losing roof work, however independent surveyors have no reason to recommend it or not recommend it.

They still get paid for their reports either way. Read on to learn more about spray foam problems.

So what are the problems with spray foam insulation?

The main argument against it for many years has been that any dampness getting in or condensation being caused, lead to rotting of roof trusses and battens and purlins.

This could cause problems in a manner of ways:

1 The rain from the outside can get in through a tile or slate that has become displaced (we know that they shouldn't become displaced once you have used this product but they do.)

2 Probably the most important concern is that interstitial condensation occurs.

Interstitial Condensation Defined

This is condensation within a material for example within a roof structure.

Interstitial Condensation is caused by there being a big difference in temperature between the inside and the outside and condensation occurring normally where the insulation meets the roof covering be it of tiles or slates. This condensation therefore then has nowhere to go but into the timber and in due course will cause rot. A roof breathes without spray on foam insulation to some extent and it also allows you to see where any dampness is coming in and repair it in this area.

Other products that say they repair roofs

We have seen a product called Stormflex that's says it does a better job at repairing tiles etc than spray on foam. We have not had experience of this so we can't comment on it.

Building Research Establishment Study on Spray Foam

The Building Research Establishment was a government owned body and is generally considered to be the main research establishment for new products and is commonly known by the name of BRE. If you are interested in visiting they have some buildings that can be walked around. In 2005/2006 studies by the Building Research Establishment and National Physics Labs found that the insulation levels of spray foam couldn't in the sample bring you values below 0.2 as are often claimed or our values of five to six tested in accordance with BS EN ISO 8990. There are values of 1.69 to 1.71 metres squared kilowatts as opposed to five or six. This is very embarrassing for many local authorities that have approved schemes based upon the industries figures. We would comment that you should never believe figures such as this that are industry produced without testing them by an independent basis such as the BRE.

British Standard and testing on Interstitial Condensation

The interstitial condensation is meant to be a problem with this type of foam insulated roofs however we couldn't find any evidence to prove this. The research British Standards did for BSI3788 which requires the taking of monthly values internally and externally and calculating whether there is any condensation on one or more surfaces. This is being done through the year in the winter and summer months. Research carried out by Glasgow Caledonian University 22 July 2009 concluded whilst fine film drops of condensation may be present during some of the time it wouldn't affect the roof timbers and therefore there is no grounds to rejecting insulating roofs on condensation risk. It makes us wonder whether it is more the fact that the water can get through the tiles and sit against the timber that causes future problems. It provides a satisfaction method of achieving the target insulation value of 0.16 watts per metre squared. This in turn doesn't relate back to the BRE's own research showing the products don't reach that thermal efficiency level unless the spray foam is very thick. We seem to recall that 130 mm was recommended.

Consensus of opinion on the internet

foam insulationIf you Google spray foam insulation good or bad you will as well as getting the various companies that install it get a number of DIY websites that come up. Many of them comment to avoid it like the plague for a variety of reasons. Many talk about problems that they have had with not being able to repair their roof when it is leaking. We saw one article where it advised that they had had to reroof in the end and the roofer had said rather than being able to save 70 to75% of the slates they were only able to save 25% of them due to the foam damage, which greatly increased the cost.




Dampness is coming through my roof, spray foam is a quick way of fixing it

If you are convinced that dampness is coming through your roof you need to take a second to consider is it really coming through your roof or is it condensation. As a surveyor we would comment that it may well be the second item condensation which you are suffering from.

We find that during the winter months we come across people that have what they believe to be dampness coming through their roof but it is in fact where the warm air from inside the property has arisen into the roof and met the coldness of the tiles or slates. Ironically this often occurs when hiding Christmas presents in the roof or getting Christmas decorations down from the roof or putting them back up in the roof. If you look at the various adverts for spray foam insulation it's very much sold as a quick fix where it is said that it can be fitted in one to two days. There is however the long term to consider as how do you fix roofs in years to come.

Never use spray foam on an old property that is Listed

foam insulationOlder properties have a slightly different construction to modern properties. They often have handmade clay tile roofs that were originally fixed by an oak peg or slates that are nailed. In both cases dampness can get into the clay tiles for example by the tiles being displaced and to the slates by nail fatigue causing the nails to rust and displace. In both cases the quick fix of a spray on foam then looks a good way to resolve the problems, with the sales techniques being that is cures roof leaks, greatly improves insulation which is always a problem when you live in an older property as you suddenly realise how much heat is needed to keep it warm. I think we mentioned earlier that it can cut heat losses by down to 80% which is what the spray foam insulation sales people say and the big problem is when you have got a listed building and the spray foam insulation is used it damages something that simply cannot be replaced. Then you ultimately have to do a proper job on the roof and replace and repair the tiles, you will then find that as they are stuck to the foam insulation many of them are unusable.


Independent Surveyors

If you truly want an independent expert opinion from a surveyor with regard to property problems, everything from roof leaks and cracks in buildings to dampness in buildings can be covered in our defects and engineers reports. We also look at whole buildings via our building surveys and structural surveys. Please contact direct on 0800 298 5424 for a discussion with us.


Commercial Property

If you have problems with your commercial property again we would be more than happy to help whether its freehold or leasehold. In addition if the property is leasehold we get involved in dilapidations claims and you may wish to look at our dilapidations website www.DilapsHelp.com and for disputes please got to our Disputes Help site at www.DisputesHelp.com .


We hope you found the article of use and if you have any experiences that you feel should be added to this article that would benefit others, or you feel that some of the information that we have put is wrong then please do not hesitate to contact us (we are only human).  

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Please see following articles which may be of interest to you:

Listed Buildings and Character Properties

Roof Problems and Information