Icynene spray foam between roof joists

Just looking for an informed opinion as I'm no expert.

Basically, an insulation company called to my mothers house at her request to look at her attic. The attic is floored with some insulation beneath the floor and she wants to keep it that way.

So Icynene is being recommended to be sprayed between the roof joists and will be then cut back to be level with the joists. There will be no plaster board put over the job.

The company rep has said the felt they would be spraying onto is breathable, but I wouldn't be sure about that, as far as I know, it is the original felt from when the house was built in the 1970's.

My main worry is with condensation rotting the joists though. The rep said the attic space would be completely sealed. Surely this causes ventilation issues??

Any help will be appreciated.

I was looking at this option also. Had an engineer friend look into it as I also have non-breathable felt.

The product you refer to is the ONLY sprayfoam certified for spraying directly onto felts. Just recently it has gained certification from the BBA (uk) and Ireland's IAB for just this type of applicaton. I had the very same concerns about rot etc and, having done loads (and I mean loads) of research into it I have no doubt that it is suitable for me.

With any product like that which is relatively new on the Irish market, there will be scaremongering among th professionals. Don't forget that the professionals built the wprst quality houses i Europe for years in this country, hence the need for everyone to be retrofitting insulation.

Sprayfoam has been in use for decades in Europe and America with no issues.

However, during my research I concluded that the Icynene was the best (and dearest!).

Have a look at their certs and ring the technical guy and he will fill you in. If you still have queries then contact the IAB and BBA in th Uk. They are most helpful.

ceekay74 wrote: »

Thanks for that, how were your concerns about the rot/ventilation put to rest?

WHile it will appear that I am on a mission here, I'm not.

My concern is the entire sealing up of the attic with the foam, not the specifics of the product. If it's sealed, moisture will get trapped.

batman1 wrote: »

What will happen is that your cold roof structure will be turned into a warm roof structure. It must be noted that the habitable area of a house must have adequate ventilation in any case. This natural ventilation (in your new warm roof ) will not cause damp or rot. I have seen 2 houses that had Icynene foam retrofitted in this way and although the attiic was nice and warm, it certainly was no more damp than the rest of the house. Does moisture get trapped in the house anywhere else?

I'm no expert but I don't see any expert here so far so I'll keep going...

A warm roof typically has a vapour control layer on the inside to protect the structure. If the foam has low permeability, then the timber joists themselves become the moisture path to outside.

Most houses are very poorly ventlilated, there's a constant trickle of threads here with people describing moisture issues.

As I understand it, the concern here isn't based on catastrophic failure within a year or 2, it's based on the roof potentially slowly rotting over the longer term.

batman1 wrote: »

If you can, go to a really old building. In many of those older buildings the space between the rafters was filled with render. This made them airtight. Those roofs are hundreds of years old.

This keeps getting thrown up to support arguments here and it fundamentally misses a point. Old buildings were reallly really drafty, they have fabulously efficient levels of ventlilation.

batman1 wrote: »

I was not convinced about the foam until I looked further into it. I am now planning on getting it done in the new year.
My advice is to go onto their website and study their certs and information. Ring the technical department.

Both the BBA and IAB certs linked off their website state that a vapour control layer is recommended unless an assessment determines it's not. Getting an independent assessment is just not something I can see many people doing.

Very best of luck with this.

Im assuming your mothers attic is a cold attic and not used for habitable space. Why didn't the company suggest lifting the flooring in your mothers attic, (they are usually screwed down) increase the quilt depth and return the flooring onto secondary joists? It's done all the time.
They are pushing a product that isn't required in a cold attic.
BTW the sloping timbers are called rafters, not joists.

"...rep said the felt they would be spraying onto is breathable, .......house built in the '70s."

Good God. You shouldn't even let these guys inside your front gate.
I agree with SAS.

"...... the average person knows nothing about insulation, ventilation."

My comment, IF YOU INSULATE, YOU MUST VENTILATE.
I don't agree with batman1.

"...... there will be scaremongering among the professionals. .....the professionals built the worst quality houses ......... in this country, hence the need for everyone to be retrofitting insulation."

The professionals built to whatever Building Regulations were in force at the time. 4" insulation was the requirement up to recently.

"Sprayfoam has been in use for decades in Europe and America with no issues."

How can you make such a generalised statement, I find it hard to believe.
ceekay74, €1,500 is twice what you would pay for properly installed quilt incl. lagging of tanks, pipes, etc. in an average size 3 bedroom semi-d.
batman1

....your cold roof will be turned into a warm roof."

This simply is not true as pointed out by sinnerboy.

"7.1 The product is combustible."

Good God again.
Do your self a favour, if you have a cold attic get a reputable company to increase the quilt at ceiling level to 12" deep and spent the €750 saved on a weekend away .

So, in the OPs case of a non breathable felt and he wants to get the foam what are his options?

Will fitting the rafter vent cards do the job, thus leaving a 50mm air gap between the insulation and felt?

ceekay74 wrote: »

I was just about to ask this very question.

I have just now come from a house that had the icynene done in 2008. The house is a bog standard dormer built in 2000 with normal bitumen felt and tiled roof. They have had no issues with moisture and had the rafters looked at in February by an engineer. No abnormal moisture was found and they are quite happy with it. And it hasn't burned down either.

batman1, could you post a rough sectional sketch of the roof showing exactly where the material was used?
It will give us a better idea of what you saw.

The professionals built to whatever Building Regulations were in force at the time. 4" insulation was the requirement up to recently.

The building regulations weren't written by nurses...;)

Building regulations mean very little in this country as they are simply not enforced. I know a young couple who bought a semi D house off the plans in the last few years. You could put your head over the wall into the next door attic. When the 'building surveyor' checked it out he said it was unacceptable for fire risks etc. So the bulder stuffed the holes with fibreglass insulation from the attic floor. Building inspector comes back and signs off on it. I kid you not!

This is the limitation - in my opinion - of taking a legalistic , minimalist approach to building regulation compliance. "What can I get away with ?"

Haven't the professionals (not all of course) been doing that for years?

I do think more of my own mother than to increase the fire risk of her roof structure like this.

Mothers aside, the foam will not increase the fire risk anywhere. It's not subject to spontaneous combustion. If some dodgy wiring or appliance was placed there then that would increase the risk of fire. If a fire, sufficient in strength to cause the foam to ignite, was in my roofspace then the foam would be the last thing on my mind! (One should always have a fire detector in the attic anyway BTW)

What the OP is asking is if Icynene foam is suitable for his situation. If the foam is fitted as set out in it's certification then I cannot see where the problem lies. The foam has obviously been through testing in order to achieve BBA and IAB certification. These indicate that the foam complies with the relevant building regulations. Are the people who certify these products wrong or misinformed in some way? I doubt it. Is it not this line of professionals who write or consult on building regulations? All products used in construction must be certified (correct me if I'm wrong). Advice given in this forum time and time again is for people to only use certified products etc.

I cannot find any evidence of where this open cell foam product was applied in the manner described by the OP caused condensation problems or rot in roof timbers. If anyone else has this evidence then please give the details.

Fitting insulation to a new build is one thing. Trying to make an old, draughty house more comfortable by retrofitting insulation is another. It's extremely difficult to get right.

From what I can gather about the Icynene open cell foam is that it is as breathable, if not more breathable than the timber rafters. I cannot see why fitting an approved product in accordance with it's certificate, by a trained and reputable installer, is such an issue when clearly any other method of insulation is not as effective.
In my house, there is 300mm of insulation fitted in the crawlspaces. Now, I would invite you to stick your head in there on a stormy January morning. It's not pleasant.

sinnerboy wrote: »

Applying any insulation directly onto non breathing felt will only conceal the inevitable condensation.

@ batman1 .
I am glad the "2008" house you saw is presenting well. But that is not to say all is well at the topsides of the rafters which were obscured from view. Condensation has happened there and will happen there again. The affect will be cumulative. Sincerely for the sake of those in that house - I hope I am wrong. But I believe they will experience rot in those roof timbers one day.

So what you are saying is that the BBA and IAB certs for the icynene foam are worthless, or at best inaccurate.

Don't get me wrong I'm not disputing your obvious knowledge in this area. I am in a position where I find that my dormer is near impossible to heat and retain heat. That is not down to lack of insulation as I have heaps of fibreglass both in the floor of the attic and floor of the crawlspaces. The problem lies in the cold air flowing through the soffit vents, going between the ceiling downstairs and floor upstairs and robbing any heat generated. Also behind the dwarf walls there is fibreglass which is loosely fitted and falling down in many places. I would imagine the walls in the rooms upstairs are leaking cold air into the house too.

I have been wrecking my head trying to figure out how I can make the house more comfortable. I looked at the sprayfoam option and it seemed to be a good job. However, I don't want to have the condensation issues down the road either.

I am open to suggestions, as the fibreglass doesn'tseem to be doing the job. Is there a way I can block off the spaces between the joists, replace the fibreglass behind the sloping ceilings ( they are only about 2 metres long and the fibreglass comes out easy enough), and improve the draughty that way. Then perhaps upgrade attic floor?

I am due to get the walls pumped with bead soon. They currently contain 50 mm white aeroboard. I'm hoping this might improve things a bit.

Perhaps the op would be interested too.

If I had the opportunity I would build a new house and get it all done properly, but that's long term....

You need to hire an clever experienced Architectural Technician to take a look.

If my budget went as far as being able to do that, I would without hesitation.
Unfortunately it doesn't at this time, unless you can make me an offer

I expect given your expressed contempt for such professionals you don't want to hear that.

I have great respect for that profession. As an obvious professional, you must see the 'cowboys' during your working life who unfortunately tend to give some reputable and competent persons a bad name. It happens in every profession.

Due to the comments posted here, I have now conceded that spraying foam onto my felt is not a good idea long term, despite what I have 'seen'. This is something that many homeowners would not be able to find out.
I still have my problem of draughts though. What do you think of the following idea.

Use sprayfoam from the wall plate across the floor of the crawlspace between the joists and up the back of the dwarf walls to meet the rafters, keeping ventilation free from the eaves through to the sloping ceiling. This will stop the draughts into the rooms upstairs while maintaining the ventilation from the soffit vents right through to the attic, as it is at the moment.

Then either leave the fibreglass in place behind the sloping ceiling or pull it out and replace it with rigid insulation(or another insulation that is better than fibreglass)

Upgrade the attic floor insulation to a better type/density.

Fill the oil tank and light a good fire