Unvented attic with open cell SPF needing exhaust fans installed on roof
Hi all,
New to GBA but have read many many threads and posts on spray foam and now am trying to tease out if the foam makers suggester for my homes issue is correct / has any downsides.
Background:
New construction home 4400 sq ft with 1500 sq ft unvented attic with 12″ 1/2 lb open cell spray foam with no burn plus intumescent paints sprayed over it. Attic houses a propane fired furnace and hvac ducts and fan duct venting for 4 bathrooms and an HRV independant of hvac mounted near gable solely to ventilate the attic.
My family and I moved in in April 2022. Project was very off scheduled and rushed many phases. Since it got warm in June (northeast area geo) the chemical smells started – noticed mostly in attic and second floor and front entry (bottom of stairs).
The installer and builder denied any smell or issue. We had an air quality report showing extremely high VOCs in the attic (5300ng/l) as well as poor air
quality (PPM, etc) and many chemicals – most prominant were pentane, proplene glyocol and ammonia.
The foam maker, Urethane Technology, thinks the issue was poor/lack of any ventilation during install making it impossible for the foam to off-gas and ‘dry out’. He used a ‘wet towel stuck in a bag’ metaphor. The foam on the surface doesn’t smell when up close to it, upon inspection in place on the wall – but if we put it in a ziploc for a day and open it is smells like rotten fish.
The foam maker (UT) says we now need to put in 1-2 exhaust fans – high power – to ventilate the attic and that that should have been done months ago. Our builder already put in an HRV trying to solve the issue but it barely affected the smell issue. Now adding roof exhaust fans to what was supposed to be a fully sealed attic seems odd.
Wondering if there is any downside we should know about? Does this root ’cause’ of the foam not being dried out/ventilated seem likely versus the foam being off ratio? Anyone else install exhaust fans for open cell on roof sheathing in unvented attic for foam odors? Would we remove these fans after a period of time and seal the attic up again to get back the original house design?
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Replies
If you put a dry towel in a bag you'd expect it to stay dry indefinitely. Following the analogy, once the products of curing have been cleared the attic should be fine, I would think it's a matter of hours or days of ventilation. It's not normal for cured foam to continue to off-gas.
is it common for foam not to cure or dry out simply because this is an unvented attic? any ideas on what should have happened if done right so we didnt need to poke two holes in the roof to deal with this?
The foam will cure in the absence of air.
What is common is for foam not to cure properly because it wasn't mixed or applied properly. I suspect that is what happened in your case.
Got it - any tips for proving that it wasnt mixed or applied properly? Signs on the foam etc?
If they are denying smells that are obviously there, you are in for a battle.
It sounds like the manufacturer is implying something is wrong. Try to get that in in writing, but good luck.
Some people talk to Henri Fennell regarding improperly applied spray foam, he has been recommended on this board.
Did you have a CIH or CEIC do your air quality tests? They would know local laws regarding residential indoor air quality. Unfortunately those laws are largely absent in the USA.
Yes we had a CIEC specialist but like you say those laws aren’t enforced for residential buildings at least that I can see. We will next go to our towns board of health to see if they have any advice. I will also reach out to Henri! Thank you for your advice.
FWIW from a CIH - Foaming an attic requires creating an auxiliary opening (~4 sqft) to properly ventilate during the SPF process. See the industry guidance to get a sense of the volume of air required to manage off0gassing during the immediate curing phase. Then the temporary hole is sealed with rigid foam board. This is almost never done, unfortunately. See articles that describe stratified humidity in attic, and you get a sense of challenges. It's hard to do and few get it right. As part of a litigation case, I once attempted to get VOC criteria used by manufacturers to indicate a successful SPF job without results. Nor could I find out VOC levels that indicated a bad job. Frustrating. How do they know/measure success? Thoughts?
VOC is not a measure of properly cured foam, and VOC readings won't even tell you what is in the air, just there is some amount of SOMETHING in the air. This is similar to the little TDS (Total Dissolved Solids) meters for water that read out in PPM: those meters tell you how many PPM of stuff is in the water, but they don't tell you what that stuff is. To actually find out what is in the water, you would have to do traditional lab tests (or a spectrographic analysis), which is much more complicated than just sticking in a TDS meter in a sample of water.
VOC is similar to TDS but for air. The problem is that VOC can come from paint, plastic, foam, cooking, smoke, just about anything. It means "Volatile Organic Compounds", and a good amount of "stuff" fits that, and the meters aren't always very selective, which makes it possible for them to display erroneous readings at times. I think people like VOC meters because they are cheap and easy to get, but that doesn't mean people use them correctly, or understand the readings.
Spray foam can cure properly and STILL show high VOC readings if the space wasn't aired out. You would really need to send a sample of the foam to a lab to determine if it cured properly with 100% certainty, and you'd need a core sample -- a long piece of foam going deep into the applied foam layer -- not just a chunk you broke off an easy to reach spot. If you can only go by VOC readings, the important thing wouldn't so much be the absolute VOC reading, it would be the trend of several readings taken over a period of time. Basically if you show high readings, then air out the space for a few days and then see low readings, you would need to check again in a few days. If the VOC readings repeatedly rise back up to where you started after several cycles of airing out, waiting, and testing, then I'd start suspecting you may have an issue. If the VOC readings show a general downward trend over time with sucessive cycles of airing out the space, then I think the manufacturer is probably right, and you should be able to ventilate the space for a while to solve the problem.
Always remember that when taking ANY kind of measurement, just because it's easy doesn't mean it's meaningful. fancy readings on meters with lots of decimal places don't mean the meters are accurate or useful, either. A classic example of this are SPL (Sound Pressure Level) meters for cell phones, which are often very inaccurate compared to calibrated SPL meters. It's always important to know the limitations of your measuring equipment, to use it properly, and, most importantly, to know FOR CERTAIN exactly what you are actually measuring when you're taking the measurement.
Bill
You are absolutely correct regarding VOC "meters" w/resp to ambient msmts. As industrial hygienists, we measure many different VOCs and other vapors. A not-so-cheap ($7-10K) "meter" is a photoionization detector (PID) that hits on various vapors, depending on ionization energy. There is no such thing as a reliable cheap VOC meter. Bad/incomplete data is worse than no data at all. And the generic "VOC" monitors have consumers thinking they are measuring something when they are likely detecting IPA or acetone or some other common vapor. What we are smelling are VOCs of some sort. We can measure particulates with particle counters (our firm certifies cleanrooms and pharmacies, so that is familiar territory). So the question is "what are we smelling?"
My unanswered query to manufacturers was "What particular volatiles (chemicals in the vapor phase) define a good or bad foam job?" Any I could not get an answer. We can measure artifacts resulting from the catalyst that are associated with foul odors, but getting a quantifiable target measurement of specific vapors has been elusive.
In this case, 12 inches is pretty thick, meaning multiple layers, and a properly cured job requires cure between layers, implying extra time, which is something contractors typically don't have. Also, the homeowner described a compressed schedule...
Bottom line - "...The only prescription is more cowbell, Baby" that is more ACH during the install process.
Am I correct? The OP said he is from the Northeast? If so, I wonder if anyone thinks that R806.5 applies here at all. Does installing 12" R42 ocSPF against the roof decking in the Northeast was the correct thing to do? Just wonder what Code this house was built under?
Armando, good points. R-42 wouldn't meet code for new construction in most places using relatively recent versions of the IRC. Open-cell foam is air-impermeable when installed more than a few inches thick, so it actually meets the requirements or R806.5 for unvented assemblies, though I have heard of enough problems due to vapor diffusion that I won't accept it on my projects.
Michael - People need to understand that the laws of physics and chemistry don't apply to prescrictive, performance nor UA alternative codes. This is a way the industry has used to cheat in good building practices.
I don't think this house in the NE meets any of these codes...
5.1.2. Where air-permeable insulation is installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing in accordance with the R-values in Table R806.5 for condensation control.
5.2. In Climate Zones 1, 2 and 3 (ONLY), air-permeable insulation installed in unvented attics shall meet the following requirements:.... (This is for Vapor Difussion Ports)
It maybe worthwhile checking moisture at the sheathing face.
Thick open-cell foam is impermeable. I forget the critical thickness but it's around four inches.
Air-impermeability it's around 5.5"-6", but it is NOT moisture impermeable. Just read the entire R806, it's not that hard to understand.