Quote:
Originally Posted by GaryGary
Hi,
Not sure that's true.
I've read elsewhere that air movement from the living space to the attic space is the single largest source of infiltration/ex filtration in a lot of homes.
I'll try to find that reference.
I know when I added insulation to my attic I first pushed the old insulation out of the way and sealed every penetration for wires, plumbing, vents, can lights etc. -- there were lots of them  All those little holes add up, and even if most of the flow out the fan is coming from the attic vents it seems like it would not take a lot of flow of conditioned living space air to offset the benefits of the attic fan?
Maybe someone can find some measurements on real attics?
Gary |
A couple of careful studies on this:
FSEC-GP-171-00
Home Energy Magazine - Ventilation :: Drawbacks Of Powered Attic Ventilators
The FSEC study found a good reduction in attic temp (20F) and about a 6% saving in AC costs. But, the AC ducts in this house went through the attic and that may have been a big contributor to the AC saving. They found a payback period of 20 years, but they paid a lot for their PV powered attic fans.
The HomeEnergy on looked at 8 homes and found that powered attic vents did depressurize the attics and caused significant flow from the living space to the attic. Not sure what kind of ventilators they were using in this one, and they may have been more powerful than the typical solar ones. They also found some other problems associated with the power ventilators.
There are a bunch of refs out there saying that AC powered attic vents don't payoff.
Gary