I’m building a new single story 3100 sq. ft. house that has hip roofs near Dallas, TX. Most of the house is under one large hip roof, but the garage and my attached shop (I’m lucky) finger out from the main hip and so are a bit isolated. The builder’s basic package is soffit vents every 8 feet and a few unpowered popup vents on the roof. I’m thinking about going with powered roof vents (instead of the passive) popup vents, one large one for the main hip and another for the garage and shop. Any thoughts on this, how do I size the powered vents, and any brand recommendations? Thanks.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Upgrading the footings and columns that support a girder beam is an opportunity to level out the floor above.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
My opinion (and possibly the concensus of the people here) are that powered vents are a waste of money.
Opinions on venting vary widely - People might be burned out about talking it over, or you might get quite an arguement stirred up.
My thoughts run this way: Vents 8' apart along the soffit doesn't sound like enough to me. I personally like to see continuous vented soffit. But he may have run some numbers on it and it's O.K.
Nothing wrong with the square vents or continuous ridge vent - Either one should do the job, as long as you have enough of them. (Ridge vents don't always work on hip roofs)
Warning: Driver only carries $20.00 in ammunition.
Use some "off the ridge" vents along with the items Boss mentioned. Used them in my house (hip roof almost to a point) and they work great. You can almost feel the air moving through the attic and its quite cool (relatively speaking) for an attic in Florida.
Mike
What about using a cupula instead of ridge vents? Would add nice look and they worked great on barns in the NorthEast.
Thanks to all for taking the time to give your opinions. I finally went with two GAF power vents and generous soffit vents. I ended up just following the recommendations provided by GAF, based on the roof pitch and footprint of my attic. Wish me luck!
Thanks for the reply. Why do you feel that powered vents are a waste of money? I thought that if you could reduce the attic temperature, you'd be saving on A/C bills and extend the life of the shingles? Is it that they don't move that much more air than passive vents? If I just go with passive vents, how do I figure out the size and how many? THanks.
Edited 6/21/2002 5:28:23 PM ET by Joe
Take a look at this thread from a few days ago. Note the comments on attic ventilation fans, as opposed to whole house fans.
http://forums.taunton.com/tp-breaktime/messages?msg=21097.1
Be seeing you...
As a minimum, I aim for one square foot of ventilation for every 150 square feet of floor space under roof. Boss is right, the amt of soffit ventilation is grossly inadequate. If I may presume to answer for him, a reason that the power vent is a waste of money is that no more air can be sucked out the top than can get in at the soffit. Size them right and natural convection will save the cost of wiring and electrical bills.
Excellence is its own reward!
I think powered vents are a waste for a couple of reasons.
First - You can do the same thing with passive gravity vents without using energy. Powered vents are expensive to buy up front, you have to pay for the wiring and energy to run them, and then pay to replace them when they inevitably wear out.
Second - The powered vents only work when it's hot. You also need atic ventilation in the winter to keep condensation from forming.
Boss
3rd, they can depressurize the house. And if the ceiling is not well sealed #### out the nice air that you just paid all of that money for to heat or cool.
Boss. You should add thatb not all combinations of ridge and soffit vents work. The soffit vents should be continuous and located next to the fascia board. This minimises the chance of snow and rain penetration. GeneL.
Along with the other comments, with which I agree, generally you want continuous soffit vents to get air flow on all areas of the sheathing; vents not only keep things cool but they keep moisture levels down and reeduce/eliminate condensation on the sheathing (and possible - dare I say it - mold growth!)
The power vents can concentrate air flow in some areas and reduce it or eliminate it in others.
To find out what works in your area, call some experienced home inspectors - they are the one's who look at this stuff day in and day out and know what works and doesn't work in your area.
It is possible your builder is doing it ok for your area, but it doesn't seem likely. Ask him if he's ever gone back to look at work he did a few years ago!
Read the .pdf document located at this link:
http://www.certainteed.com/pro/ventilation/pdf/PrinciplesAtticVent.pdf
I'll be in the minority. I like and use power vents. I have three for a 4,000 square foot home. They are Broan. They come on based on the temperature of the attic, which can be staggered. 1 at 95, 1 at 100 and the last one at 105. Simple romex wiring and a switch. No big deal.
They are figured by calculating the cubic (I said cubic) feet of your home, square footage times wall heights, right. Then figure out how much of an air exchange you want. Once every 30 minutes? Thats fairly slow. Once every 5 minutes? Thats really moving.
Then pick the fan you like with the appropriate CFM, and start multiplying the number of fans you need to achieve the total CFM you need.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927
Help me learn something here. I can't figure out what the Cu Ft of total home has to do with it. Maybe if you are talking about a whole house exhaust but the idea of an attic fan is to change the air in the attic so Cu Ft of that space is all that should be considered, no? Is yours a house exhaust or an attic vent system? Where are you in terms of climate?Excellence is its own reward!