Solar attic fan

Xringer · 07-19-12, 08:37 AM

There are tar-like stains on the outside of my house, around the vents.
That's caused by out-gassing from the (1956) wood, and maybe roofing tar paper.
I have climb a ladder with pressure-washer sprayer to clean those stains.

The hot air in my attic accumulates in the peak, and had little effect on the ceilings of the living space.
But, as the day wears on and the peak hits 120f, the air down at the insulation becomes very warm.
I think the hot air just soaks into the insulation, warming the wood and the sheet rock under it.
Radian heat from the roof bombards the insulation directly.
The insulation and the ceiling it covers, warms to the room temperature, of the attic..

Before long, the living space starts to warm up. I can reach up and feel the warmth of the ceiling.
Radian heat is raining down.

When possible, we pull down the attic stairs and let cooler air updraft into the attic.

But, when we have the AC running and the house is sealed, there is very
little natural outflow of air.

Picture a can with two holes in the top, sitting in the sun. At first the air expands with the heat and some air flows out.
But once that's over, stagnate hot air will just sit in the can.

So, installing a fan in the east side vent (see pic above), sucks hot air out,
and pulls cooler outdoor air into the attic from the west side vent.
That air flow keeps the 120f air off the attic floor, and helps keep my living room ceiling cooler.
So, my Sanyo ASHPs don't have to work as hard..

07-19-12, 08:37 AM	#14
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	There are tar-like stains on the outside of my house, around the vents. That's caused by out-gassing from the (1956) wood, and maybe roofing tar paper. I have climb a ladder with pressure-washer sprayer to clean those stains. The hot air in my attic accumulates in the peak, and had little effect on the ceilings of the living space. But, as the day wears on and the peak hits 120f, the air down at the insulation becomes very warm. I think the hot air just soaks into the insulation, warming the wood and the sheet rock under it. Radian heat from the roof bombards the insulation directly. The insulation and the ceiling it covers, warms to the room temperature, of the attic.. Before long, the living space starts to warm up. I can reach up and feel the warmth of the ceiling. Radian heat is raining down. When possible, we pull down the attic stairs and let cooler air updraft into the attic. But, when we have the AC running and the house is sealed, there is very little natural outflow of air. Picture a can with two holes in the top, sitting in the sun. At first the air expands with the heat and some air flows out. But once that's over, stagnate hot air will just sit in the can. So, installing a fan in the east side vent (see pic above), sucks hot air out, and pulls cooler outdoor air into the attic from the west side vent. That air flow keeps the 120f air off the attic floor, and helps keep my living room ceiling cooler. So, my Sanyo ASHPs don't have to work as hard.. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less.. Last edited by Xringer; 07-19-12 at 08:39 AM..