# Spray foam insulation... to use or not to use?



## Builder Bob (Dec 26, 2007)

I was interested in using spray foam insulation for a new house to be build this spring and was wondering if anyone in the forum had any personal experience with any of the products out there?  Any reviews, positive or negative, etc.  The potential energy savings appear to be good, I would just have to have the HVAC sized accordingly with an heat/air exchanger included.  

Thanks, 

Bob

Ps.  If this is not the correct location for this please forward accordingly.


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## JohnnyBravo (Dec 27, 2007)

spray foam is very expencive. there are companies that use mesh to cover the wall and then blow celulose. its not that much more money than fiberglass but has a greater r value. if the house is not too big and you can afford the spray foam you may see a return. it all depends on how long you live there and how much the price of heating goes up. watch out if you do any in the attic you have to leave a vented air space between the sheeting that the shingles are mounted to.


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## d.n.f. (Dec 27, 2007)

It is expensive but the stuff is really good.  Emits nothing once it has been cured.  Doesn't need a vapor barrier so factor that lack of install into your costs.

Blown in insulation emits junk 24/7 into the environment (your lungs).

Just make sure your installer knows what he is doing and make sure you are getting the right foam.


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## guy01 (Dec 27, 2007)

I was under the impression you didn't need a airspace when used in attics because there is no temperature differential to cause sweating


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## d.n.f. (Dec 27, 2007)

99% sure you don't need an airspace in the attic with sprayfoam.  SIPs in the roof don't have an airspace so spray foam is kinda like a do it yourself SIP.


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## guy01 (Dec 27, 2007)

OK I tried but can't figure it out -sip's- I don't know the acronim


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## Hokerer (Dec 27, 2007)

SIP = Structural Insulated Panel

http://www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic=11740


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## d.n.f. (Dec 27, 2007)

Guy said:
			
		

> OK I tried but can't figure it out -sip's- I don't know the acronim



Structural Insulated Panels.

Basically they are filled with foam and have a material on the outside and inside (material varies).  For example, my friend has a sip roof which has metal on the outside (normal roofing) R45 foam, and then metal on the inside which he covered with t and g.  A crane lifted the two panels together and they were bolted in-situ on site.  Trick.  You can do walls, basements, and I think even floors now.

Kind of the new-future of building.

Those basement blocks are a kind of sip if you have seen them.   You build them then fill them with concrete.


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## Builder Bob (Dec 27, 2007)

The foam blocks are called ICF's (insulated concrete forms) and are even more expensive than the spray foam.  The average ROI for the spray foam is about 4-5 years.  The avg. cost per sq. ft. in the walls is $1.75 and $1.90 in the ceiling.  I think this will be the insulation type for the next house, no drafts to worry about.  It will require a O.A.K. for the wood stove and a heat air exchanger for the HVAC system to get fresh air into the house.

Bob


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## burnham (Dec 27, 2007)

It has a tendency to "push" wires and recessed lights outward/down when it expands. You really have to do a good walk through prior to insulating this way. The same non-english speaking gents who do the regular insulation do the spray in as well, so you generally can't trust them to have your best interests in mind at all times. It is also difficult to add wiring after the job is done. Lately I've seen it used in select locations in new homes, mostly in the end bays, in the basement outside bays, and over the sill in the basement. If I were building a new house I may use it in a few areas, but not the whole house. I think the money could be better spent in other places. I also think you can make a house a little too tight, the need for an air exchanger doesn't appeal to me.


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## Reggie Dunlap (Dec 28, 2007)

I'm a builder here in VT and we use a lot of spray foam, usually the closed cell. If it's done correctly it prevents any ice damming issues, which probably isn't a concern in your location but it's a problem anywhere you have a lot of snow. I usually use a combination of foam and blown-in cellulose in ceilings and fiberglass in walls. The foam is so expensive that I don't often do the whole house. I use it in any sloped ceiling and then spray cellulose in the flat ceilings. I like to strap the ceiling first, then spray the foam out to the face of the strapping. This eliminates any conductive heat loss through the rafters.

If money were not an issue I would foam every exterior surface on every house I build. There are potential cracking problems if the foam is not mixed or applied correctly. I like to wait a couple of weeks before sheetrocking to make sure the foam hasn't cracked before covereing it up.

reggie


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