Wednesday, January 29, 2014

Slow Progress In Solar-Powered Attic Ventilation

I missed the boat with a customer having only gable vents, no possibility of opening up soffits.

Observations were reported here:

Wednesday, September 5, 2012

A Residence Attic Ventilation Review 

I had pleaded with the roofer who would have opportunity in Summer 2013, to try something new. Please don't cut in roof high static vents, where there were none to start. High vents and gable vents clash unpredictably, with little net air circulation. I would come in after the reroof, and install a solar-powered attic fan at roof center. That fan, on hot Summer days, would draw cooling air through both gables. I got no call. Driving by last Fall, I found the usual static vents, over the peak on North side of roof.

No roof high vents, still, visible from the street.

I blame the missed opportunity of experiment, and still-hot attic for this customer, on slow progress in inspiring a manufacturer to offer a suitable fan. I had bought a  Solaro Aire  , with built-in PV array, for this job.

I brought the fan back to the factory and discussed concerns and wishes for something better. This fan has a 12.5" bore, and should require not more than a 12.5" roof hole. I was troubled by wasted metal spinning of rounded shape in the base, not a factor in aerodynamics, and then of not having means of adding a bellmouth draw pipe under the fan in the attic. Troubled that fixes I might devise should be offered by the manufacturer.

I am appalled by the installation procedure for the Solaro fan, as presented in this video . A 19" hole is commanded through shingles and sheathing. Nails are in the way of lifting shingles for the fan tuck of course. Just hack them off by swinging a reciprocating saw over sheathing, under all shingle layers. Rely on poor blind application of caulk, smeared-off in sliding, to stop wind-driven rain up the roof. Hope the reciprocating saw didn't develop leaks through tears. I would NEVER follow those instructions.

My wishes of better and of ever-constant learning, are driven by progress installing a Costco US Sunlight attic fan, as reported in this photo album:

I am unimpressed with aerodynamics of the US Sunlight fan, but accepted it. The customer made the choice for his convenience and cost savings. I insist upon sealing an adapter plate into the roof for any fan penetration, 4" bath fan, 8" static vent, 14" fan here, whatever. The fan body is only a rain cover, minimizing concern about blind tucking. Shingles are cut in a circle only slightly larger than the sheathing cut, and there is a maximum of shingle overlap upon the real seal of the adapter plate. High-quality caulk can be applied copiously with full visibility, and yet there is minimum reliance on caulk. I wish never to rely on caulk, at all.

Here are graphics conveying my wishes of better, to Solaro, and to all manufacturers.

The simple adapter plate is set atop roof membrane, sealed at top to the roof membrane. All involved lower shingle courses rest on the adapter plate.

Fan electronics are serviceable/ swappable, without impact on roof sealing. A bug-blocking screen will get fouled, and may be serviced from the roof as needed. Good fan aerodynamics include smooth draw through a bellmouth. If fan blades of larger diameter than the roof cut are better, let the fan reside below the flare or bellmouth. Let us get over treatment of attics as inaccessible trash pits as treated by the Solaro crew.

Here is my only Costco solar fan installation, over an accessible attic. 

1 comment:

laya said...

Thanks for the post. Know the roofing cut plan and terminology
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