Author Topic: Spray Foam Insulation  (Read 1088 times)

Offline Crazy tools

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Spray Foam Insulation
« on: May 24, 2021, 12:11:15 AM »
Looking for some information on doing spray foam in the attic.
Any data points would be appreciated.
Do you really see a difference in energy bills in the summer and winter?
Does it help with keeping the second floor cool?
Any mold concerns due to not having any air movement in the attic?
Any concern with not noticing a roof leak until all the foam is soaked?
Do you see a difference in overall comfort?
 

I have a colonial home that I'm thinking about doing spray foam. 2nd story ac unit blows strong and cold, but stays on for hours to keep a temperature of 71-72 degrees. Outside temp was sunny and 85.
Wondering if I should so spray foam or maybe an attic fan would be enough. My attic currently has Batts of insulation with quite a few inches of blown in cellulose.

In NJ I know there is a 7 year interest free loan to cover the cost, so I would be paying about $57 a month. Would love to hear if there are any grants besides for the loan.

Offline efflpetzel

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Re: Spray Foam Insulation
« Reply #1 on: May 25, 2021, 01:50:29 AM »
I did spray foam whole house,
It's a no brainier, house stays warm in winter without the heating constantly running & cool in summer without ac continuesly running

Offline joeb1

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Re: Spray Foam Insulation
« Reply #2 on: May 25, 2021, 06:00:09 AM »
You canít double insulate an attic
If there is already insulation in the floor of the attic you gotta pull it out if you want to put insulation in the rafters or wonít have any airflow and will cause many issues

Offline Crazy tools

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Re: Spray Foam Insulation
« Reply #3 on: May 25, 2021, 07:56:23 AM »
You canít double insulate an attic
If there is already insulation in the floor of the attic you gotta pull it out if you want to put insulation in the rafters or wonít have any airflow and will cause many issues
There can't be anything on the floor? Or specifically cellulose ?

Offline pointer

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Re: Spray Foam Insulation
« Reply #4 on: June 14, 2021, 05:54:58 PM »
What are the current incentives for spray foam insulation on NJ?

Offline efflpetzel

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Re: Spray Foam Insulation
« Reply #5 on: June 14, 2021, 09:43:08 PM »
There can't be anything on the floor? Or specifically cellulose ?
Anything

Offline skyguy918

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Re: Spray Foam Insulation
« Reply #6 on: June 14, 2021, 10:08:38 PM »
Anything
Do you have something on your attic floor even after spray foam that you're worried about?

Offline efflpetzel

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Re: Spray Foam Insulation
« Reply #7 on: June 14, 2021, 10:13:49 PM »
Do you have something on your attic floor even after spray foam that you're worried about?
I donít have anything on the floor

Offline Crazy tools

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Re: Spray Foam Insulation
« Reply #8 on: June 15, 2021, 02:54:21 AM »
Anything
I've seen many houses with spray foam and insulation Batts in the joists between the ceiling and attic floor.
What types of issues would there be? I've also seen spray foam done and the gable vents were left opened. Was this possibly done to allow for some sort of airflow in the attic?

Offline skyguy918

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Re: Spray Foam Insulation
« Reply #9 on: June 15, 2021, 10:01:27 AM »
I've seen many houses with spray foam and insulation Batts in the joists between the ceiling and attic floor.
What types of issues would there be?
It's not a death sentence by any means - there are many mitigating factors that could make it 'safe' to leave insulation on the attic floor. But generally speaking the recommendation of the experts is to remove it. This article has a nice summary:
https://www.greenbuildingadvisor.com/article/three-reasons-to-remove-attic-floor-insulation-in-a-sealed-attic

The basic issue is that if the attic floor is not really well air sealed (which realistically is often the case), there is air being exchanged between the living space and the attic. That makes the air in the attic more humid than outdoor air, and since when you do spray foam you generally close up any attic venting, there's no way for that humidity to escape outside anymore. Leaving the insulation on the floor means that the temp in the attic in the winter will be significantly colder than in the living space, potentially allowing the spray foam itself to become a condensing surface, which brings moisture problems into the attic.

Most of this is based on the work of the 'godfather' of modern building science Joe Lstiburek - here's his article on this topic of conditioned attics:
https://www.buildingscience.com/documents/insights/bsi-077-cool-hand-luke-meets-attics

Bottom line, I would think any type of insulation on the attic floor has this issue, unless it was also an air/vapor barrier (like cc spray foam) - though obviously there's no reason one would have that on the floor and the roof deck.
I've also seen spray foam done and the gable vents were left opened. Was this possibly done to allow for some sort of airflow in the attic?
This on the other hand does sound like a death sentence (though of course I'll caveat that I'm not anything close to an expert on this subject). You fix the moisture issue, because it can escape to the outside, but you're killing the effectiveness of the insulation. When the insulation is on the floor of the attic, it's okay to have a vented (ie unconditioned) attic space because the insulation still separates between the living space and the unimpeded airflow from the outside. But once you move to spray foam, where the insulation is on the underside of the roof, keeping the attic freely vented to the outside just introduces outside air inside the insulated space.

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Re: Spray Foam Insulation
« Reply #10 on: June 15, 2021, 10:17:50 AM »
It's not a death sentence by any means - there are many mitigating factors that could make it 'safe' to leave insulation on the attic floor. But generally speaking the recommendation of the experts is to remove it. This article has a nice summary:
https://www.greenbuildingadvisor.com/article/three-reasons-to-remove-attic-floor-insulation-in-a-sealed-attic

The basic issue is that if the attic floor is not really well air sealed (which realistically is often the case), there is air being exchanged between the living space and the attic. That makes the air in the attic more humid than outdoor air, and since when you do spray foam you generally close up any attic venting, there's no way for that humidity to escape outside anymore. Leaving the insulation on the floor means that the temp in the attic in the winter will be significantly colder than in the living space, potentially allowing the spray foam itself to become a condensing surface, which brings moisture problems into the attic.

Most of this is based on the work of the 'godfather' of modern building science Joe Lstiburek - here's his article on this topic of conditioned attics:
https://www.buildingscience.com/documents/insights/bsi-077-cool-hand-luke-meets-attics

Bottom line, I would think any type of insulation on the attic floor has this issue, unless it was also an air/vapor barrier (like cc spray foam) - though obviously there's no reason one would have that on the floor and the roof deck.This on the other hand does sound like a death sentence (though of course I'll caveat that I'm not anything close to an expert on this subject). You fix the moisture issue, because it can escape to the outside, but you're killing the effectiveness of the insulation. When the insulation is on the floor of the attic, it's okay to have a vented (ie unconditioned) attic space because the insulation still separates between the living space and the unimpeded airflow from the outside. But once you move to spray foam, where the insulation is on the underside of the roof, keeping the attic freely vented to the outside just introduces outside air inside the insulated space.
Is there any solution for noise between floors - if insulation isn't an option?

Offline Crazy tools

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Re: Spray Foam Insulation
« Reply #11 on: June 15, 2021, 10:20:04 AM »
It's not a death sentence by any means - there are many mitigating factors that could make it 'safe' to leave insulation on the attic floor. But generally speaking the recommendation of the experts is to remove it. This article has a nice summary:
https://www.greenbuildingadvisor.com/article/three-reasons-to-remove-attic-floor-insulation-in-a-sealed-attic

The basic issue is that if the attic floor is not really well air sealed (which realistically is often the case), there is air being exchanged between the living space and the attic. That makes the air in the attic more humid than outdoor air, and since when you do spray foam you generally close up any attic venting, there's no way for that humidity to escape outside anymore. Leaving the insulation on the floor means that the temp in the attic in the winter will be significantly colder than in the living space, potentially allowing the spray foam itself to become a condensing surface, which brings moisture problems into the attic.

Most of this is based on the work of the 'godfather' of modern building science Joe Lstiburek - here's his article on this topic of conditioned attics:
https://www.buildingscience.com/documents/insights/bsi-077-cool-hand-luke-meets-attics

Bottom line, I would think any type of insulation on the attic floor has this issue, unless it was also an air/vapor barrier (like cc spray foam) - though obviously there's no reason one would have that on the floor and the roof deck.This on the other hand does sound like a death sentence (though of course I'll caveat that I'm not anything close to an expert on this subject). You fix the moisture issue, because it can escape to the outside, but you're killing the effectiveness of the insulation. When the insulation is on the floor of the attic, it's okay to have a vented (ie unconditioned) attic space because the insulation still separates between the living space and the unimpeded airflow from the outside. But once you move to spray foam, where the insulation is on the underside of the roof, keeping the attic freely vented to the outside just introduces outside air inside the insulated space.
Very nicely explained.
My question now is, do I trust my local "experts" regarding this issue.
I never asked them point blank about my attic insulation, but they came to give me a quote for spray foam and didn't mention anything about removing my insulation Batts and cellulose..

Offline skyguy918

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Re: Spray Foam Insulation
« Reply #12 on: June 15, 2021, 10:21:31 AM »
Is there any solution for noise between floors - if insulation isn't an option?
Why would noise between attic and living space be an issue? And if you're talking about 2 floors that are being used (and conditioned similarly), it's a non-issue.

Online Euclid

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Re: Spray Foam Insulation
« Reply #13 on: June 15, 2021, 10:23:11 AM »
Why would noise between attic and living space be an issue? And if you're talking about 2 floors that are being used (and conditioned similarly), it's a non-issue.
In Lakewood (and Brooklyn, I think) people use finished attics for living space.

Offline aygart

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Re: Spray Foam Insulation
« Reply #14 on: June 15, 2021, 10:24:55 AM »
In Lakewood (and Brooklyn, I think) people use finished attics for living space.
Then the issue would be the insulation between the living space and the unfinished portions.
Feelings don't care about your facts

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Re: Spray Foam Insulation
« Reply #15 on: June 15, 2021, 10:28:16 AM »
Then the issue would be the insulation between the living space and the unfinished portions.
Why do you need insulation if it's fully encased in spray foam?

Offline Crazy tools

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Re: Spray Foam Insulation
« Reply #16 on: June 15, 2021, 10:29:49 AM »
Why do you need insulation if it's fully encased in spray foam?
May have been there from before the space was finished ...

Offline skyguy918

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Re: Spray Foam Insulation
« Reply #17 on: June 15, 2021, 10:36:14 AM »
In Lakewood (and Brooklyn, I think) people use finished attics for living space.
Then the issue would be the insulation between the living space and the unfinished portions.
+1. If there's insulation on the floor that's not a finished space. I will add though that on that article I linked to there is a comment about sound issues due to something called flanking, but it sounds unlikely to be a real life issue - more like building science nerds thinking through potential issues.

Very nicely explained.
My question now is, do I trust my local "experts" regarding this issue.
I never asked them point blank about my attic insulation, but they came to give me a quote for spray foam and didn't mention anything about removing my insulation Batts and cellulose..
Honestly, I don't think it's a big issue either way. Issue #2 (gets in the way of laying down the spray foam) from the article is certainly something the insulatiuon contractor should be able to speak to - but it's certainly possible for them to get a good seal just by moving the existing insulation around while spraying and making sure it gets put back. Issue #3 (odor and air quality) can probably be gauged just by going up there and seeing if it looks/smells really terrible. And even the main issue (moisture issues) is unlikely to be a problem in NYC if you're putting a decent amount of insulation on the roof. See this comment from the article:
Quote
For the attic to be a wintertime dew point problem it has to be really thin insulation at the roof deck, or really fat insulation at the attic floor. In US climate zone [4A - NY metro area] as long as [30%] or more of the total-R is at the roof deck, the average temp in the attic will be above the dew point of the conditioned air, and little to no moisture accumulation occurs.

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Spray Foam Insulation
« Reply #18 on: June 15, 2021, 10:52:37 AM »
+1. If there's insulation on the floor that's not a finished space.
What do you mean by this?

Here's the scenario I'm talking about - the layers:
1. Roof
2. Spray foam
3. Finished attic (the actual airspace of the room)
4. Floor of attic
5. No insulation/hollow space
6. Ceiling of room beneath
7. Room beneath

Because of layer 5, any noise (eg footsteps) from the finished attic will be heard in layer 7. Typically there would be insulation that minimizes noise between floors...

Offline skyguy918

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Re: Spray Foam Insulation
« Reply #19 on: June 15, 2021, 11:09:06 AM »
What do you mean by this?

Here's the scenario I'm talking about - the layers:
1. Roof
2. Spray foam
3. Finished attic (the actual airspace of the room)
4. Floor of attic
5. No insulation/hollow space
6. Ceiling of room beneath
7. Room beneath

Because of layer 5, any noise (eg footsteps) from the finished attic will be heard in layer 7. Typically there would be insulation that minimizes noise between floors...
So first of all, I'd say many - if not most - homes don't have insulation or sound dampening in the ceiling/floor between living spaces. However, if you already have it, or want to put it in, it does not create the issue being discussed here. If you finished the attic it is (or at least in theory should be) a conditioned space. That means heating/cooling to keep the temp in there reasonable. That eliminates the entire issue with not having a vented attic.