Spray Foam for attic - Good or Bad

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  #1  
Old 02-27-14, 11:05 AM
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Spray Foam for attic - Good or Bad

Hey Guys,

I had an energy audit and the team recommended having the attic (currently unconditioned) treated with spray foam on the inside of the roof decking and removing the current 35 year old fiberglass between the second floor ceiling and the attic. What are the pros and cons of doing this, and is it a sound method for increasing the efficiency of the home. I do have my second floor AC air handeler in the attic which gets very hot in the summer. I don't believe the ducting is insulated. Either way, what are your thoughts?

Thanks,

Bryan
 
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  #2  
Old 02-27-14, 12:06 PM
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Expensive, could be practical but would there be an alternate approach?
 
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Old 02-27-14, 03:18 PM
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I would not want the AC unit inside the conditioned space of the house, which is what this would do for you.
 
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Old 02-27-14, 05:03 PM
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I would not want the AC unit inside the conditioned space of the house, which is what this would do for you.
??????? Really? Why would you not want the air handler inside the conditioned space? That is where it belongs. Homes like this that have air handlers and duct work in an unconditioned attic see the largest benefit from moving the thermal boundary from the ceiling of the house to the roof deck.

I say it is good, but it really depends on your situation. Spray foam will be expensive. You will need at least 2" of closed cell spray foam to establish a vapor barrier. You can do a combination of spray foam and batt insulation to save money, but you need at least 50% of the R-value in foam to avoid condensation issues.

Do you use the attic for storage? The alternative is to beef up the floor insulation to like R-60 with blown in or batts. Insulate the ductwork as best you can. And get the attic to be very well ventilated.
 
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Old 02-28-14, 08:23 PM
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The attic is used for storage, along with the air handler.
Closed cell is impervious to water, correct? How would one find a roof leak before if rotted the roof sheathing with a closed cell application?
Would open cell be better in this location?
A spray foam installer today told me to apply 6" if closed cell and when I asked hom about a roof leak he looked puzzled and asked why that would ever happen??? Seems possible as the roof reaches the end of its life and problematic if the leak can't be detected?
What's the average cost of spray foam per square foot? I'm still waiting for the quote from earlier today.
 
  #6  
Old 03-01-14, 04:54 AM
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Prices vary, but I often use $1 per ft² per inch. You will need to check local codes to see if they will require a fire rated covering, and if you insulate the bottom of the roof, the ends of the attic will need it as well. Enclosing an attic usually requires 1.5X as much coverage as the attic floor, or more depending upon the slope.

Here's a link for some reading
How to Build an Insulated Cathedral Ceiling | GreenBuildingAdvisor.com

Bud
 
  #7  
Old 03-01-14, 05:04 PM
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Open cell does not act as a vapor retarder and that is something you need. Otherwise you will have condensation on the bottom of your roof deck and not even know it. Yes, it will be difficult to know when the roof leaks with closed cell foam. Based on what I have read, leaks that do occur and go unnoticed have damage that is more localized than with other types of leaks. It is important to be sure your roof remains in good condition and is replaced in a timely manner.
 
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