I live in Nashville Tennessee area, a lot with lots of trees all around my home.
My home is gable roof, 7/12 and 9/12 pitches. The main section (7/12) is 72’ long and rafters 27’ each side…
I have continuous vented vinyl soffit 2’ wide. There are baffles in the soffits for insulation.
I have ridge venting on all ridges, ± 100 LF. I also have 3 turbines on the rear (north side) with tops below ridge line.
Issue: Is my attic venting: poorly, okay, or very well?
Are the turbines pulling air through the ridge vents thus not removing hot air effectively?
Or due to the trees, does the ridge vents not have enough wind or low pressure to draw the air from the attic?
A roofing contractor stated that I should remove the turbines.
I believe that the turbines are moving more air than the ridge vents and both are drawing from the soffits. They were turning today with a little wind blowing 5-8 mph and 65 degrees. Sun and partly cloudy. Temp on sun side of attic 72, at shaded side turbine 69.
I don’t feel the turbines are ‘short circuiting’ the ridge vent flow (or pulling air through the ridge venting and not the soffit venting.)
I am reluctant to remove or close the turbines. I am very familiar with fluid flows and thermal dynamics from working in the chemical plant industry.
Difficult question to answer on a forum. You certainly have plenty of ventilation openings, both low and high, based on your description. Knowing the temp. difference between the exterior and the interior of the attic might help on a hot day. Knowing the depth of the insulation and the temp. diff. on a cold winter day might also help.
What is going on inside your attic? How many baffles are placed at the eaves to allow for ventilation? Are any exhaust vents from the home terminated into the space? Does the attic open into the garage or the house? What is the attic access cover made from?
Based on your description and what is typical in the mid-west, I would almost suspect your ventilation may be too great on the high side. If there is a larger area of ventilation on the high side, you risk putting your attic under negative pressure and drawing air from the interior of your house. This is an energy loss and a potential moisture/condensation concern in the winter as that warm moist air condensates on cold framing components. The low side should have more ventilation area so that the air is pushing into the attic from the eaves, putting the attic under positive pressure which will then draft out of the high side. You might be able to find an inspector on here who would consult with you for a reasonable fee. An onsite evaluation would definately be the best.
My initial thoughts were very similar to Cameron’s. I would have to assume the roofer suggested removal of the turbines simply because your ventilation system would be considered on the “high” end of venting. I’d ditto Cameron’s concern that your more than likely generating a negative pressure situation (at least at times) in your attic which will affect the interior air, increasing your energy costs during the summer especially and possibly creating a moisture problem during cooler months.
Still, there are lots of unasnwered questions to be sure. Best advice from me would be to find a NACHI inspector and have him/her come out to advise and/or inspect.