Increasing airflow into attic
My roof is hipped, divided into two sections.
The main section is slightly higher and lacks a ridge vent. There are two vents, one with a fan, the other a turbine. The fan recently stopped working.
The smaller section, perhaps half the size of the larger section, has a ridge vent.
The eaves are small. The make-up air is provided by vents. The vents are 2 inches across with louvers on the outside and wire mesh on the inside. One louver was removed to allow for a vent for my ERV. See attached photos.
One theory for why the fan stopped working is that the vents are undersized and insufficient make-up air enters through the vents, straining the fan. I assume some air is coming from inside the house since the insulation is very uneven. In places, you can see the drywall that is the ceiling of the floor below.
The attic is considerably warmer than the outside whenever it is either warm or sunny. I am sure some of this heat enters the house, but I think the bigger problem is that both the air handler and the ERV are located inside the attic.
So far, I haven’t noticed any problems with excess humidity in the attic.
I wasn’t planning on replacing the fan with another fan. But it seems like I should increase the airflow into the attic. Any thoughts?
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Replies
bsawers,
One big benefit to increasing the inlets to the attic at the eaves so that they are of a larger volume than the outlets near the peak is that it will slightly pressurize the attic, which will discourage the movement of air from the house through leaks in the ceiling. The attic fan has been doing the opposite.
I'd suggest adding the code required volume of vents, but dividing it 60 / 40 between the eaves and peak. One easy way to do that at the eaves is by simply using larger circular vents. The big box stores sell them up to 6" in diameter. At the peak I'd add Box or Turtle vents. Turbines can act much like motorized fans and extract too much air.
Don't worry unduly about the attic temperature. Even well ventilated attics are much warmer than outside in the summer. Air-sealing the ceiling and adding insulation is a better response than trying to over-ventilate. Having the air-handler and ERV there is always going to be a problem, whether the attic is hot, or very hot.