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Old 06-10-2010, 10:04 AM   #1
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Best approach


My attics have R30 batt insulation and full length soffit vents, front and back, which are open, and Cobra ridge vents (previously perforated metal). Despite this, I have never been able to demonstrate any airflow into the soffits, or out of the ridge, and attic temps do rise. The shingles are black.

The roof seems to radiate heat into the 2nd floor and directing more airflow (via dampers) doesn't seem to help.

Which, if any of the following, would be helpful?
a) remove batts; foam the joists, then return batts
b) foam the inside of the roof
c) radiant barrier inside of the roof
d) any combo of the above

I had sized the a/c at 3.5 tons (down from 4), but the contractor talked me into a 2 stage 4 ton (which doesn't never runs in 2nd). In retrospect, the 3.5 unit would have given me about 300 more CFMs.

When the system was installed, the return ducting in the basement was upgraded, and 2 lower return grills were added (downstairs) and the upstairs grill was enlarged. This has improved comfort downstairs, but has only added minimal gains to the upstairs.

I had looked into zoning, but have ruled that out.

What say you?

Edit: 1:00 PM, went up in the attic to do some antenna work and it was hot as hell (not quite as bad as on a 90 degree day. OD temp low 70s. It's been cold these mornings (50s overnight), but it's still hot from the last hotspell. With windows open and the attic hatch cracked, there was a little movement of tissue when the wind blew.


Last edited by veesubotee; 06-10-2010 at 12:46 PM. Reason: added post script
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Old 06-10-2010, 01:00 PM   #2
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Best approach


Knowing the outdoor and attic temp, would have told us more, then just telling us it was real hot.

Radiant barrier would probably be you best bet.

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Old 06-10-2010, 03:08 PM   #3
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Best approach


Quote:
Originally Posted by beenthere View Post
Knowing the outdoor and attic temp, would have told us more, then just telling us it was real hot.

Radiant barrier would probably be you best bet.
Sorry. I just took the temperature. It was 118, OD was 83.
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Old 06-10-2010, 03:15 PM   #4
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Best approach


30 to 35 hotter then outdoor temp is not unusual.

Once the sun is shinning on those shingles. The temp goes up quick.

RB, will keep a lot of that heat from getting in.
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