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ergnut
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New Member
Posts:19
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| 07/16/2008 1:03 PM |
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My question about spray up foam is answered, and I think additional blown cellulose will be the best method to reduce heat build-up from the attic to second floor living spaces. I'd guess this is a combination of conduction and radiation, which leads me to think a radiant barrier will be beneficial.
In general, do these product work effectively (produce a measurable result)?
Does anybody have direct experience with installing a staple up radiant barrier in an existing, insulated attic? What brand of barrier did you use, and are you happy with it?
Thanks
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Brock
Registered Users
Basic Member
Posts:444
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| 07/16/2008 3:08 PM |
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| I hate to jump on this thread, but our situation is so similar. In our new home we also have R44 blown in with some storage up in the attic space with ridge vents on a hip roof. For the heck of it I put a thermometer up there and if it’s sunny it hits 125-130F (what is normal?). Our HVAC contractor said that is good, it means the A/C isn't leaking to the attic. I am also toying with the idea of adding a radiant barrier to the underside of the roof or adding a wind turbine, like you see on barns that spin in the slightest wind to exhaust air from the space. I have seen a couple of them on newer homes around here lately. I guess the other option would be adding a couple roof vents or some sort of powered exhaust although I would prefer not. |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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ReadyToRetire
Registered Users
Basic Member
Posts:212
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| 07/16/2008 5:15 PM |
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ergnut,
I'd considered a reflective barrier about 20 years ago, but my roof is built on trusses -- it would have been a true bother to staple it up evenly. Recently I was searching on line for something else and came across a system that blew in "chips" of what looked like ALized mylar to create a reflective barrier on top of the existing fiberglass, but you first had to level and smooth the existing insulation, which would add effort. I've not tried it, not read any reviews of it, and didn't price it, but it seemed like a rational idea.
Good luck,
Larry
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Alton
Registered Users
Advanced Member
Posts:662
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| 07/16/2008 5:40 PM |
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Brock,
If I remember correctly, wind turbines used as vents in roofs, do not work very well. They are also prone to leaking during hard rains. |
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Alton C. Keown
Residential Designer and Construction Technology Consultant
Auburn, Alabama
E-mail: alton at auburn dot edu |
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Brock
Registered Users
Basic Member
Posts:444
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| 07/16/2008 8:30 PM |
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I had wondered about rain in windy conditions. They look pretty "open". I could put it above the garage portion where the storage is and put a garbage can to collect rain underneath it.
I guess is it better to try to add insulation or try to somehow exhaust the warmer air or is it not really an issue? In winter it is 0F up there and I don't worry about it then, and actually adding more vents would cool it even more... |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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Donaldson
Registered Users
New Member
Posts:92
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| 07/17/2008 7:30 AM |
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| Your best most efficient attic space is one that is completely sealed off. If you used spray in foam and sealed the soffits and the vents with at least 4 inches of foam then the attic temp would never be more than 8-10 degrees diffeerent than the house temp. This makes your HVAC work more efficient as it is not having to battle extreme heat in the summer. I have seen some "Spider" HVAC systems when one flex run travels over 30 feet. The flex insulation tubing is not designed to battle 120-150 degree temps in the attic so the cold air coming out at the end is not cold but mildly cool. Sealing off you attic will increase the life of your roof shingles as it doesn't allow the "baking" from underneath during the summer, a big problem her in FL where a your lucky if you get 10 years out of a 25 yr shingle. Sealing off the attic helps to strengthen the home in case of high winds as it doesn't allow for the wind to get under the roof through the soffits. Also if you HVAC system has a leak it isn't leaking into outside temps but helping to maintain the attic at house temp and lastly it provides you with air conditioned storage space. Your energy saving will typically pay for the investment in under 8 yrs. |
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