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Old 10-18-2010, 04:54 PM   #1
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Foam Insulation


I just had my contractor open my sofit vents for continous air flow, and now plan on getting a new furnace, the furnace man suggest i get more insulation in the attic so he recommended a guy. This company comes over today and tells me the best way to insulate an attic is to use this spray foam, in addition he tells me the ridge and intake vents needs to be closed off. IN essence he is telling me the attic with this foam stuff, is air tight no air coming in or out. (to me based on what I've heard hear and other sources, this sounds crazy.) then he says all new high end homes are doing this, this is coming from a company who makes their living off of installing insulation, what do you make of this?

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Old 10-18-2010, 06:06 PM   #2
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Foam Insulation


He is a salesman selling his product.
Of course you need what he is selling... NOT!

Ask your contractor about adding more loose fill or batt insulation. It will be equally beneficial and lots cheaper.

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Old 10-19-2010, 09:41 AM   #3
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Foam Insulation


You will almost assuredly void your shingle warranty. Check with the manufacturer of your shingle roof before choosing to have the attic insulated with spray foam, most shingle manufacturers have warranty exclusions for spray foam reducing the warranty in half.

The practice is becoming more and more common, but I am very interested in seeing how the shingle roofs hold up in the next 5-10 years. However in my experience even the high end homes here still have batt or blow in fiberglass attic insulation.

Many many churches will have an insulated roof deck, which is similiar to spray foam on the bottom side of the sheathing. These roofs seldom last longer than 20 years because the added expense of installing a ventilated nail base can nearly double the cost of a job and most people don't understand how essential ventilation is to the life of a shingle. Furthermore I have heard rumor of the off-gas from the spray foam actually also causing harm to the shingle further accelerating the break down.

Truth be told in my opinion we do not yet have conclusive evidence one way or another in regards to spray foam on the bottom side of a roof deck, w/o ventilation. I'm sure there are accelerated weathering tests done out there, but I don't often beleive in those type tests. Time will tell.
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Old 10-19-2010, 10:16 PM   #4
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Foam Insulation


Maybe the furnace would benefit from removing all of the roof ventilation? ~this i am not sure~

Your roof would suffer from removing the ventilation. Do not eliminate the roof ventilation.

Last edited by RoofDiagnostics; 10-19-2010 at 10:17 PM. Reason: typo
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Old 10-19-2010, 11:19 PM   #5
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Foam Insulation


yea thats the exact same they are proposing to do with my attic. spray foam seal it shut
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Old 10-20-2010, 12:46 AM   #6
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Foam Insulation


Quote:
Originally Posted by Grumpy View Post
You will almost assuredly void your shingle warranty. Check with the manufacturer of your shingle roof before choosing to have the attic insulated with spray foam, most shingle manufacturers have warranty exclusions for spray foam reducing the warranty in half.

The practice is becoming more and more common, but I am very interested in seeing how the shingle roofs hold up in the next 5-10 years. However in my experience even the high end homes here still have batt or blow in fiberglass attic insulation.

Many many churches will have an insulated roof deck, which is similiar to spray foam on the bottom side of the sheathing. These roofs seldom last longer than 20 years because the added expense of installing a ventilated nail base can nearly double the cost of a job and most people don't understand how essential ventilation is to the life of a shingle. Furthermore I have heard rumor of the off-gas from the spray foam actually also causing harm to the shingle further accelerating the break down.

Truth be told in my opinion we do not yet have conclusive evidence one way or another in regards to spray foam on the bottom side of a roof deck, w/o ventilation. I'm sure there are accelerated weathering tests done out there, but I don't often beleive in those type tests. Time will tell.
Stupid question here Grumpy, but does that apply to aluminum shingles? Personally I wouldn't think so but this isn't my dept.
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Old 10-20-2010, 10:55 AM   #7
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Foam Insulation


I wouldn't think so with metal shingles but you'd have to contact your local building department and the manufacturer of the metal shingles.
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Old 10-20-2010, 01:14 PM   #8
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Foam Insulation


They are really advertising this foam stuff, saw it in the paper....I just can't see sealing off ALL ventilation and air flow in the attic, after all the crap I went through to get my roofer to come make (9 momths later) to open up my sofits again, and make continuous intake vents, I just can't see closing it all off, sealing the ridge vent, and spending 4 times what fiberglass insulation would cost, someone is getting rich off this, thank goodness for places like this to educate us consumers, G
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Old 10-20-2010, 09:51 PM   #9
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Foam Insulation


it all has to do with the dew point and where its located
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Old 10-20-2010, 09:52 PM   #10
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Foam Insulation


The new 2009 IRC has the requirements listed here: http://publicecodes.citation.com/ico...006_par003.htm

And Building Science is right there too: http://www.buildingscience.com/docum...archterm=attic+


It’s been known for a long time venting is mainly for condensation in the attic, not cooling the shingles: http://www.fpl.fs.fed.us/documnts/pdf2002/rose02a.pdf

Another: http://www.buildingscience.com/docum...r-all-climates

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Old 10-20-2010, 10:48 PM   #11
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Foam Insulation


so spray foam doesnt hurt the shingles at all
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Old 11-02-2010, 11:09 AM   #12
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Foam Insulation


Quote:
Originally Posted by GBR in WA View Post
Itís been known for a long time venting is mainly for condensation in the attic, not cooling the shingles: http://www.fpl.fs.fed.us/documnts/pdf2002/rose02a.pdf

Another: http://www.buildingscience.com/docum...r-all-climates

Gary
I really could not disagree more.
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Old 11-02-2010, 12:30 PM   #13
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Foam Insulation


“Adequate attic ventilation is a long-standing requirement in building codes for moisture control. However, conditioned, unvented attics can reduce residential energy needs and are allowed by the code under certain conditions. Such assemblies are sometimes called cathedralized attics because, as with cathedral ceilings, the insulation is in the rafters and/or roof deck. The primary benefit of cathedralized attics is the ability to locate HVAC ducts inside conditioned space, where duct leaks and heat losses/gains are not detrimental to the home''s energy bill.” From 2006 IRC: http://docs.google.com/viewer?a=v&q=...kV-ztF0DKEvW7w

March 2002, from your peer’s magazine:
Conclusions

The following conclusions are based on data from our numerical model:

  • The greatest influence on roof temperature is geographic location. The mean roof temperatures for Miami and Green Bay, Wis., for example, differ by 18 degrees Celsius.
  • The direction a roof faces has the second greatest influence on average roof temperature (in excess of 1.44 degrees Celsius in the east through south-to-west range studied, but the real difference is greater because other directions, such as north, will be cooler).
  • The color of roofing materials influences the mean temperature of a roof system slightly less than direction (1.45 degrees Celsius average for these parameters).
  • Ventilating the area under a roof deck reduces the average temperature 0.5 degrees Celsius (about one-third the influence of the direction or color and one-thirty-sixth the influence of geographic location). Even with wind assistance, ventilation reduces average roof temperature about half as much as using white rather than black shingles.
  • Within the ranges studied, slope has the least influence on average shingle temperature.
http://www.professionalroofing.net/a...2/feature2.asp


I really could not disagree more.”------- Which particular point?



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Old 11-02-2010, 09:44 PM   #14
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Foam Insulation


wow good rebuttal....i sit waiting :P

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