Greening my home 2.3
July 8th, 2010 by KenricYesterday I wrote:
“However at night the readings go down to 65 degrees on both of the sensors. Given that the air temps are 90 at night, these numbers are totally wrong. I can’t figure out what’s going on, because I have tested both sensors by putting them inside the house, inside the frig, etc… and they work fine. I guess I’ll have to get on the roof when they read 65 again and feel them.”
So last night I went up on the roof when both my sensors were reading 67, outside temperature was probably 90. When I got on the roof it felt really cool. I put my hand on the foam roof and it was cold. I grab the sensors are they are cold. So I guess they are working right.
I can’t believe the roof is around 65 degrees. The AC was running and I felt portions of the roof right above the ducts. Those were definitely cold, but the portions of the roof that were far away from the ducts were also cool.
I am going to guess that my roof rafters have virtually no insulation and that the AC ducts are cooling the space in between the roof. I have no attic and a flat roof so there is only 8-10″ from the bottom of the ceiling indoors to the bottom of the foam roof.
Posted in Green Home | 3 Comments »
Stumble it!
I think it has less to do with your AC and more to do with this- http://www.globalspec.com/reference/14387/Night-Sky-Radiant-Cooling-Influence-on-Outdoor-Thermal-Imaging-Analysis-pdf
“The surface temperature of objects directed to the sky with a large angle of view is often decreased below the temperature of the surrounding air.”
By kurt on Jul 8, 2010
Had to look Ouray up on a map. Never heard of it. It’s near Telluride in SW Colorado. Another luxury home rental with a spectacular view, no doubt.
Whether you have insulation depends on when that house was built. Anything mid 70′s or later will definitely have insulation between the roof joists. There may be gaps and it may have settled.
No doubt some heat is getting in from the roof via conduction, especially during the day. There may be some convection as well if the insulation was poorly installed or has settled and there are gaps.
The infrared detector will tell you exactly what is going on. Still think your big problems are your windows and air infiltration.
By Another Investor on Jul 8, 2010
On a somewhat related topic, I was at Costco this weekend and noticed they were selling an All Purpose Ventilator fan from U.S. Sunlight. I’m thinking about putting one of these in my attic. Unfortunately, I only have one gable vent in my attic and the rest are small O’Hagin type vents, which an installer told me would not work with these fans. Still, it’s solar powered, so there’s no electric cost for me to run it, and the unit qualifies for a 30% tax credit, so I don’t really see any drawbacks to putting it in.
By Shaun on Jul 12, 2010