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Old 10-12-2011, 06:14 PM   #1
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Attic w/ HVAC Conditioning ?s


Hi,
I was hoping I didn't need to post a ? but I am stumped. I plan on installing soffits and soffit vent baffles and solar powered attic fan in gable vent (cost prohibitive to do ridge went in metal roof) then putting Roxul Wool 3.5" deep btw 23" OC rafters and 2" R-Tuff polyisocyanurate board to bottom surface of rafters. The problem I have is how to insulate the area where the attic (an addition) crosses over the existing roof. Please see pics of the whole attic on my picasa album.
https://picasaweb.google.com/1040152...eat=directlink

Thanks,
Doran

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Old 10-14-2011, 01:51 PM   #2
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Attic w/ HVAC Conditioning ?s


Sorry bad link:
https://picasaweb.google.com/1040152...tioningProject

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Old 10-14-2011, 10:06 PM   #3
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Attic w/ HVAC Conditioning ?s


electric air handler?
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Old 10-15-2011, 07:56 PM   #4
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Yes, its electric with the heat pump outside.
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Old 10-15-2011, 08:30 PM   #5
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Blown in insulation?
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Old 10-15-2011, 08:32 PM   #6
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Attic w/ HVAC Conditioning ?s


I'm confused as to the problem. Your attic is conditioned?
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Old 10-16-2011, 08:36 AM   #7
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Attic w/ HVAC Conditioning ?s


Doc,

I love you quote by the way. Probably one of my 3 favorite movies of all time and highly underrated.

Attic is not conditioned.

First thing I would recommend is air sealing, air sealing, air sealing.

Stop the loss of conditioned air from the living space and the ductwork/HVAC system.

After that, rigid foam (poly iso) will give you the best R-Value per inch where you have limited insulation depth and are on the slope. I will need to be covered in most cases for an ignition break but there is where you can use fiberglass to cover it.

The biggest thing that sticks out to me is the amount of air movement in the attic as evidenced by the dirty insulation.

I have stolen this pdf from GBR but it hold application in this case.

http://www.google.com/url?sa=t&rct=j&source=web&cd=1&ved=0CDMQFjAA&url=h ttp%3A%2F%2Fwww.finehomebuilding.com%2FPDF%2FFree% 2F021105092.pdf&ei=4d2aTsvhBanb0QHRj6W7BA&usg=AFQj CNFpl-zXra-KMIljVhw6uxT5Szy-FA
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Old 10-16-2011, 06:14 PM   #8
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Attic w/ HVAC Conditioning ?s


Thanks WIndows on Wash. Thanks, I will review and seal. Would you put the fiberglass/poly iso board in that space where there is red pex tubing (see pic) now. Part of the old eave is exterior and part isn't but if I onlt did exterior bays, I would be stopping insulation halfway through the bay. Does that make sense.

BTW, we are in NOVA too.
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Old 10-16-2011, 08:31 PM   #9
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I would prefer to insulate that pex directly with something like spray foam.

The biggest issue is that folks want to treat the attic as a mixture of spaces. Ex. Storage is okay in the attic if it does not prevent you from having a proper insulation layer.
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Old 12-07-2011, 06:20 PM   #10
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OK, we removed most of the ply and built a 2x4 platform over to later place plywood on for storage. We had 18" of loose cellulose blown in and where we kept the plywood, we had cellulose blown under it. Now can we put rigid foam on the ply which is on the cellulose and then a ply cover over that?
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Old 12-07-2011, 08:25 PM   #11
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If you want. That is definitely going the extra mile.

The insulation short circuit should only be a small cross section but if you want to go the extra mile, it can't hurt.

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