AboutTodd E. Miller Expertise I am available to answer any questions pertaining to residential (or other sloped) metal roofing. I have knowledge of most available products but I like to approach projects from a "needs" basis and analyze them individually. Additionally, I can answer most questions about building ventilation.
Experience I have worked for a manufacturer of residential metal roofing since 1980. I currently serve as President and have been involved with a wide variety of projects of all types across the world.
Organizations I am a board member for Metal Construction Association, Metal Roofing Alliance, the local United Way, our church, and our son's school.
Publications Over the years, I have had articles appear in several trade journals including RSI, Remodeling, and Qualified Remodeler.
Education/Credentials I have a B.A. in Communications and have also completed three years of training with the E-Myth Academy.
Question QUESTION: I live in NE Ohio and I currently taking bids on replacing my roof. I am leaning on using power vents as opposed to ridge vents because a) I was told by several contractors and ridge vents manufacturers that I do not have enough ridge available and b) I already have one power vent (non-working) on my attic so power is available. I was told that I have only 44 ft of ridge vent available when I need 70+ ft to meet the 1 sq ft venting/150 sq ft attic floor standard.
I have a ranch house in a shape of a T. The closest roof style is a cross hipped roof. The footprint of the attic is about 2700 sq ft with pitch about 5/12. One of the T is 28 ft x 40 ft with the 28 ft facing North and South - this includes attached unheated garage, living room, and open porch. The other part of the bar is 36 ft x 40 ft with the 40 ft facing North and South - this area contains the main living area.
One contractor and 2 manufacturers of ridge/power vents recommend 2 power vents because of the shape of the roof. The contractor adviced me to treat each bar of the T as a separate attic space.
I do have 2 static vents which may be available for the power vents. One static vent is in one bar of the T and the other static vent is in the other bar of the T. The static vents are about 28 ft apart and the current power vent is in between these vents. If I draw a line going from the west end of the house to the east end of the house the line is 68 ft, one static vent is about 21 ft from the west end of the house and the other static vent is about 56 ft from the west end of the house. The west end of the house contains the 28 ft x 40 ft section. All of these vents are near the ridge line.
Any advice as to where to place 2 power vents?
The other question would be I am considering getting either 2 Airvent P-12 (1170 CFM 10 year warranty) vents or P-15 (1500 CFM lifetime warranty) vents. Any advice as to which pair to get?
ANSWER: I would agree in your case that power fans seem appropriate. It sounds like the static vents are close to centered on each ridge / roof section that you do have. I would probably stick with thise locations.
You want to be able to pull more air than what your soffit vents can provide. I assume you have good soffit venting. I would probably go with the bigger fans.
I hope this helps some.
Todd Miller
www.asktoddmiller.com
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QUESTION: Thank you for your response.
Today I met with a roofing contractor. He agreed that there was not enough ridge for a ridge vent and he wants to put in one power vent.
He disagreed with the option of 2 power vents for the following reasons:
1. chances are that one of the power vents would end up overtaking the other power vent so one power vent would be the intake and the other power vent would be the exhaust
2. the only way the 2 power vent system would work would be to physically separate both parts of the T so that each vent would be serving a separate attic space. He mentioned putting a curtain barrier between the 2 attic spaces. The curtain part sounds kind of "suspicious" to me.
Separately, I was told by the manufacturer that this probably would not be a problem if both fans are of equal CFM, spaced far enough apart, and have plenty of intake.
Who in your opinion is correct, the contractor or the manufacturer?
Separate question, should each power vent be on a separate thermostat and humidistat - in other words it is possible and advisable for one power vent to work and the other power vent not be working, or should they be wired up in such a way so that both power vents would function at the same time?
Thanks
Mark
Answer Without a doubt having adequate intake is important. I do not have a way to gauge whether you have enough.
I would definitely wire the two fans together.
As long as both fans are operating and you have adequate intake vents to feed them, there is no way for one to feed the other.
