Spray foam insulation and moisture

[teetee]

Topics like this always makes me feel like it is up to interpretation of different parties and often lack of evidence.

Yay:
https://insealators.com/residential/spray-foam-insulation-and-moisture-control/


Nay:
https://www.silversurfers.com/lifes...sons-you-should-have-your-spray-foam-removed/

I think bottom line is the foam blocks air flow which will start trapping moisture. Moisture is bad for wood.

 

[braumeister]

Without following your links, we have no idea what point you're trying to make.

 

[lawman]

My home has it..It's a trade off ..I think it does indeed help with heating and cooling costs but my concern is that any small leaks in the roof will go unnoticed..What I like about it is that it allows good visibility/inspection of electrical and water lines in the attic. Having an air conditioned attic is also a plus

 

[rk911]

but, sometimes, life's a pregnant dog and THEN you die. it's really both, often simultaneously.

 

[Jerry1]

The biggest concern I have with foaming my attic is the cost. I had a pre-COVID quote of about $10K (for a 1700 sqft ranch) and I can't imagine what it would cost now. I'm too much of an accountant to buy something like insulation that has virtually no chance of paying back. If I live in this house for 20 more years, I'd have to save $500 per year in utility cost. That's somewhat possible if utility costs keep going up, but my plan is only to live here for another ten years. I can turn up the thermostat quite a bit for $1000 per year.

I'm looking at a less costly option. Maybe just a few inches of cellulose in the attic. Enough to prevent the ice dams. The thing that intrigued me about foaming the attic is that it would leave my mechanicals uncovered. I live on a slab so all my heat and electrical are run through the attic. I'm not excited about burying everything under 2 feet of cellulose.

 

[lawman]

The biggest concern I have with foaming my attic is the cost. I had a pre-COVID quote of about $10K (for a 1700 sqft ranch) and I can't imagine what it would cost now. I'm too much of an accountant to buy something like insulation that has virtually no chance of paying back. If I live in this house for 20 more years, I'd have to save $500 per year in utility cost. That's somewhat possible if utility costs keep going up, but my plan is only to live here for another ten years. I can turn up the thermostat quite a bit for $1000 per year.

I'm looking at a less costly option. Maybe just a few inches of cellulose in the attic. Enough to prevent the ice dams. The thing that intrigued me about foaming the attic is that it would leave my mechanicals uncovered. I live on a slab so all my heat and electrical are run through the attic. I'm not excited about burying everything under 2 feet of cellulose.

You would love my house. I can walk all around in he attic and have easy access to a.c., ducts. plumbing and electrical

 

[Jerry1]

You would love my house. I can walk all around in he attic and have easy access to a.c., ducts. plumbing and electrical

I would love that, except for the cost to obtain it. Also, I have a low pitched roof so I cannot stand up in my attic. Though crawling around without any cellulose would be nice - for sure.

 

[RetiredAt55.5]

The biggest concern I have with foaming my attic is the cost. I had a pre-COVID quote of about $10K (for a 1700 sqft ranch) and I can't imagine what it would cost now. I'm too much of an accountant to buy something like insulation that has virtually no chance of paying back. If I live in this house for 20 more years, I'd have to save $500 per year in utility cost. That's somewhat possible if utility costs keep going up, but my plan is only to live here for another ten years. I can turn up the thermostat quite a bit for $1000 per year.

I'm looking at a less costly option. Maybe just a few inches of cellulose in the attic. Enough to prevent the ice dams. The thing that intrigued me about foaming the attic is that it would leave my mechanicals uncovered. I live on a slab so all my heat and electrical are run through the attic. I'm not excited about burying everything under 2 feet of cellulose.

Also, if the attic isn't used for living space (per your subsequent post), it would seem more efficient to insulate the attic floor since otherwise you're losing a fair amount of heat into the attic.

 

[ImThinkin2019]

Also, if the attic isn't used for living space (per your subsequent post), it would seem more efficient to insulate the attic floor since otherwise you're losing a fair amount of heat into the attic.

We have a shallow pitched roof so it's not usable for storage, etc. Therefore the attic floor is what's insulated. We replaced the thin fiberglass matts with a perimeter of spray foam and the majority central area is now cellululose.

The spray foam was pretty easy to install in the tight areas, right up against the rafter baffles. The cellulose was much cheaper and makes sense when used for the majority of the attic floor. We like cellulose much better than blown fiberglass, based on our experience.

The spray foam actually holds the rafter baffles, facilitating airflow. This house used to have ice dams but no longer does.

The attic re-insulation makes the living area much more comfortable. It used to feel cold in here in the winter, but no longer.

 

[latexman]

Topics like this always makes me feel like it is up to interpretation of different parties and often lack of evidence.

I think bottom line is the foam blocks air flow which will start trapping moisture. Moisture is bad for wood.

The foam blocks incoming air/moisture AND traps any air/moisture that is already behind the gap. In each specific case, figure out which is best, fill the gap or not, and do it.

 

[teetee]

The foam blocks incoming air/moisture AND traps any air/moisture that is already behind the gap. In each specific case, figure out which is best, fill the gap or not, and do it.

I think the moisture barrier is the solution. According to https://www.energyvanguard.com/blog/what-happens-when-you-put-a-plastic-vapor-barrier-in-your-wall/ and

, if there are two layers of moisture barrier, one on the outside of the framing, and one on the inside of the framing behind the drywall, then it blocks the moisture from temperature differential during winter and summer.



Too bad there is no way this can be done without tearing the existing house down to the frame.

 

[Alan]

Spray foam insulation has been on the news over here a lot this year as mortgage lenders are very reluctant to give a loan on houses that have it. Here is an article on the issues.

https://thinkplutus.com/learn/spray-foam-insulation/

Theoretically, spray foam insulation sounds like a great way to protect your home from cold and drafts, as a higher-end insulation option that’s been on the market for about 30 years.

However, it can be a serious issue if you need to finance a property, whether that’s remortgaging, applying for an equity release product, or buying a new home. Often sold as a higher-performing insulator than mineral wool, spray foam is present in thousands of homes, in wall cavities, flooring and lofts.

The problem is that most mortgage lenders and NO equity release providers will touch properties with spray foam insulation for various reasons.

 

[triangle]

With a proper vapor barrier, I don't see how the spray foam insulation would cause a moisture problem. But in a retrofit situation, that could be the issue.

I half expected this thread to be about the potential side effects of spray foam off-gassing. I don't remember the source but saw a TV news report years ago (something like 60 minutes) of a few families tearing the roofs off their house to make them livable again after a bad spray foam install. Where the root cause was the person spraying not being experienced or properly educated or without showing enough attention to details when mixing the chemicals together. Creating a toxic environment that could not be "aired out" in just a few days or weeks. My takeaway for looking into this a few years ago was that the spray foam from a can is relatively safe, as the chemical recipe was followed in the factory. But getting spray foam mixed onsite requires more care.

Matt Risinger ("build show" guy) focuses a lot on energy efficiency but I don't think he has not gone full in spray foam in his custom home business. I have not watched him lately, but I think this video is one example of him building for a client who is very sensitive to chemicals.

Another spray foam video where a person from the UK also mentions in his comment (highlighted if following the link below) that lenders in the UK have the same fear of moisture getting trapped.

 

[NgineER]

Installed properly spray foam is a great solution for energy efficiency and providing an airtight home. Improper design and installation could lead to long term issues

 

[Hilltopper]

We just sold the home we built with sprayed foam insulation in the roof.. I thought it was great. Yes, you are effectively heating/cooling your attic, but I think it probably had a negligible effect on the cost to heat/cool, given an overall energy efficient home. The only concern I had when we built was whether the foam would be an issue if the roof leaked (trapping water/moisture). We had the option to use open-cell or closed-cell foam, and chose the open-cell for the roof with the understanding it would help mitigate that risk. I.e., open-cell for the roof and closed-cell for walls. At least that was the rationale.

 

[Masquernom]

I have read about an issue with closed cell spray foam. It has a higher insulation value than open cell foam, but cures to a much harder foam. I've read about wood members shrinking/moving/bending as they dry out, leaving a gap between the cured closed cell foam and wood. The open cell foam apparently has some flexibility to stay connected to the wood as it moves around over time. Also I believe the open cell foam also allows some transmission of moisture? Unfortunately, the open cell foam is not as insulating as the closed cell foam. However, I'd still go that route as I believe sealing air flow may be more important than the insulation factor.

 

[OldShooter]

We just moved into a new lake house. The insulation system was called "Blow In Blanket". Very soft and fluffy. Claimed R-41 vs typical fiberglass at R-35.

​

The process was as follows: The insulation contractor stapled clear poly over the studs, then made small holes through which they blew in the insulation. Once done they stapled a second layer of poly over everything. The sheet rock and wood ceiling boards then effectively sealed the poly against the studs. A few problem areas were foamed, but probably not even 1% of the job. IMO the air seal provided by the insulation is nearly perfect and the house is extremely tight.

Per code, we do have an air exchange box. (https://www.lifebreath.com/wp-conte...MAX-Specification-sheet-01-01-18-1.pdf?x19032) The HVAC guy said to not worry about it too much, but to turn in on when humidity is high enough to condense on the windows in winter and any time there are odors/cooking that we want to get rid of. There is a wall control box next to the thermostat.

Maybe something like this would work for you?

 

[Masquernom]

In a tightly sealed house, with an air exchange unit, I believe I'd run it a couple of times every day. Installations like that I've seen usually have some sort of timer you can program to run the air exchange unit occasionally. Especially in a new house where carpet and new construction materials are offgassing.

 

[OldShooter]

In a tightly sealed house, with an air exchange unit, I believe I'd run it a couple of times every day. Installations like that I've seen usually have some sort of timer you can program to run the air exchange unit occasionally. Especially in a new house where carpet and new construction materials are offgassing.

We'll see.This is all new for us -- never had a gadget like that before. The HVAC guy's default setting was to run 20 minutes out of every hour. I have no idea what that means in terms of air volume. All I can see is dollar bills being pumped out of the house via the residual energy in the expelled air.

 

[Masquernom]

We'll see.This is all new for us -- never had a gadget like that before. The HVAC guy's default setting was to run 20 minutes out of every hour. I have no idea what that means in terms of air volume. All I can see is dollar bills being pumped out of the house via the residual energy in the expelled air.

It's supposed to be an air interchanger. The outgoing air exchanges it's heat with the incoming air. So you don't lose many BTUs. I thought they'd set it up to run periodically.

 

[OldShooter]

... you don't lose many BTUs ...

Every BTU, however, is one I have bought and paid for. Claimed efficiency is only 85 to 75%.
​

 

[Masquernom]

That's true. Plus you pay for the electricity to run the fan.

 

[JoeWras]

This stuff scares me.

Maybe I've worked on too many 100 year old homes that have nothing, yet have been soaked to the bone in floods. They don't mold. I guess the ancients knew about mold -- just let the air flow.

All our mold work is in "newer" homes, or old homes retrofitted.

But I live in the south where we can be loose with insulation for the winter, so my view is tainted.

 

[NgineER]

Every BTU, however, is one I have bought and paid for. Claimed efficiency is only 85 to 75%.
​

True - but the reason for the HRV being installaed is because your house is much more energy efficient thereby reducing the $$ spent on heating and cooling the unconditioned air leaking into your home.

 

[finnski1]

Every BTU, however, is one I have bought and paid for. Claimed efficiency is only 85 to 75%.
​

Yes but if you have built a really "tight house" you need to have proper ventilation.

I have 2 ERV's in my wall and run them all winter when the windows are all shut to get a reasonable fresh air exchange. If you can afford 2 houses, surely you can afford healthy air. Mine actually reverse direction of the fan every 70 seconds and runs the air thru a ceramic honeycomb core to lessen the temp differential on intake and exhaust.