Attic spray foam insulation question - time sensitive

3,371 Views | 15 Replies | Last: 2 yr ago by TravelAg2004
schwack schwack
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AG
We have a contract on a house (to be a rental) and during our cursory inspection today we found that they have spray foamed the roof decking. They sealed up the ridge vent & the soffit vents. That's good, right?

An issue we do see is that the bathroom fan & kitchen vent hood are not vented thru the roof. This is a new renovation, no one has lived in it yet, so no moisture build up or mold there. Obviously this needs to be addressed.

Anything else we need to look for with foam insulation?

Our inspection period runs out next Thursday. Thanks - appreciate any input.


El_duderino
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I'd say it's almost a requirement to have a whole home dehumidifier w/fresh air intake installed in a spray foam home. So see what the hvac setup is
AgProgrammer
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AG
Was the HVAC updated as well? On renovations that weren't built with foam originally in mind, you are likely looking at needing a variable speed HVAC plus dehumidifier to keep the moisture levels in check.

The only other thing I'd be nervous about was the state of the roof decking before they sprayed it. Once it's covered, you don't know if there was any water damage from roof leaks, etc. But not much you can do about that now.
schwack schwack
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AG
New roof & new HVAC. Will have to dive deeper into what kind. I'm sure there is no dehumidifier though.

House built in '86. Brick. Single pane windows. In great shape for a rental, but we've never dealt with foam before.

Thanks for replying.

F2Aggie
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AG
They remove the blown in insulation sitting on the ceilings?
schwack schwack
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Quote:

They remove the blown in insulation sitting on the ceilings?

Yes, they did. That's good, right?

TMoney2007
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AG
Humid air will tend to rise and collect at the ridges of the attic space.

From what I've seen you can run a dehumidifier in the attic space or you can have a small AC duct that vents to the attic space. It can keep the air moving a little bit up there and keep the humidity down.

I doubt a house built in the 80's is going to be near tight enough to cause issues with not getting enough fresh air in the house. I would still vent exhaust fans and hood vents out of the attic. Putting more moist air up into the attic space isn't going to help your cause.

On a positive note, with a semi-conditioned attic space, your HVAC equipment should last longer and be more efficient.
mosdefn14
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AG
There's a roofer on the board I'm sure, but I looked into this and my roofer buddy said there was only 1 or 2 30 year shingles (at the time) warrantied to be used above a fully encapsulated attic. And you had to make sure to seal your soffits & other points for air entry.
tgivaughn
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AG
CODE or not
All exhaust venting needs to get outside
Foamed in attics must also vent combustion air, gas appliances in that space OUT, some kits can be found to do so
IMHO and am sticking to it
Agzonfire
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Definitely would want those vents run to the exterior. Might be easier to poke through the soffit rather than run through roof. At least they sealed the other vents and removed existing blown. Like others have said, make sure there's no gas combustion in the attic that is unvented.
rondis23
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AG
Random question, but why does the ceiling blown attic insulation have to be removed if you spray foam?
dudeabides
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AG
The main reason is prevent moisture problems. The idea behind spray foaming the roof deck (and not the ceiling floor) is to bring the attic airspace into the air envelope of the house and seal the attic from the outside... opposite that of a traditional vented attic with blown insulation.

If you leave the blown/bat insulation on the attic floor after insulating/sealing the roof with spray foam, the attic will be cooler in winter than if you had removed the insulation and the spray foam will be even colder than the attic air. If the spray foam is cold enough, and the humidity (now trapped in the attic) is high enough, water will condense on the spray foam and drip on to the warm attic floor insulation. ...Hello mold and ceiling stains.

There are additional benefits too, such as possible improvement in air quality, as old insulation often has dead critters and their poop in it after years of service. Having that inside the air envelop of the house doesn't sound good to me.


rondis23
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AG
I have always read this recommendation to remove the old insulation, but never really got an explanation. That makes sense. Thank you!
schwack schwack
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Sorry for the late response to all of your posts & thank you for the input. We close on the house soon & they came off the price to remedy this & a few other things.
Jason_InfinityRoofer
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mosdefn14 said:

There's a roofer on the board I'm sure, but I looked into this and my roofer buddy said there was only 1 or 2 30 year shingles (at the time) warrantied to be used above a fully encapsulated attic. And you had to make sure to seal your soffits & other points for air entry.


Yeah. It's a thing. From a legal standpoint GAF and Owens Corning has warranty verbiage about spray foam. Certainteed has no limitations.

From a practical standpoint…there is not anything inherently different about any of these shingles that makes one super special over the others. Think of it like Ford voiding your engine warranty because you put a lift in your truck. So is it a big deal? That's your call.

The fact is that the warranties in place require proper attic venting and I don't always see proper ventilation, so those warranties would technically be void as installed anyway.

More over, I'd argue a spray foamed deck is better for the shingles from a heat standpoint over an attic sitting at 140 degrees.

All that said, I'd worry more about the foam being done right and exhaust vents being piped outside than I would any shingle warranty because of the foam.
https://linqapp.com/jason_duke --- JasonDuke@InfinityRoofer.com --- https://infinityrooferjason.blogspot.com/
schwack schwack
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AG
Quote:

All that said, I'd worry more about the foam being done right and exhaust vents being piped outside than I would any shingle warranty because of the foam.
Thank you!

TravelAg2004
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AG
The big thing I'd look at is they did they actually make the attic now part of the conditioned space by bringing conditioned air into it and treating it like any other room?

If they just sprayfoamed everything but then didn't add a vent and return, you're going to get humidity build up and depending on how long it's been going on, could have some issues.

Here's an article that explains it in more technical details: https://www.energyvanguard.com/blog/high-humidity-in-a-spray-foam-attic-part-2
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