My upstairs is too warm. Even with a ridge vent and soffit vents and fiddling with the AC vents inside, its still much warmer than downstairs. On a hot day the ceiling is warm to the touch. I have about 18″ of blown in insulation and altho there are probably a dozen baffles to ensure the insulation did not restrict the flow of air up from the soffits, it’s still hot. So Im considering an attic fan. <!—-><!—-><!—->
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Im not concernind about the installation (Ive done it before and have access to electricity in the attic), my question is: do I need to close up the ridge vent? Im concerned that the attic fan with suck air thru the ridge and not up from the soffits (or gable vents — I have 2) and therefore minimize the amount of hot air that is removed from the attic space.<!—-><!—->
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Thoughts? Maybe install it and see how it does and perhaps close up the ridge vent later?
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Replies
I'd concentrate more on intake. If you don't have enough soffit vent and install a power vent with the ridge vent closed, you'll create negative pressure in the attic which will suck your conditioned air through any small openings that exist.
IMHO, power vents are a good solution in very few instances.
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Might try closing off the gable vents first.
These could be short cutting the ridge vent/soffit vent system.
As previously suggested, I'd block the gable vents first, as an experiment. A piece of plastic, even a heavy duty garbage bag, and four pieces of duct tape will do the job well enough.
Side note: The house I'm currently living in is an older place with three gable vents and no other attic venting. There's a thermostatically controlled fan mounted on one of those gable vents. It's set to go on a a fairly low temperature, for a hot climate, about one hundred degrees.
That fan moved a lot of air, without doubt, but it quit working this year. This past week has been nearly as hot as it ever gets around here but I've yet to notice a difference in heat gain, inside the house.
This leads me to suspect that, with gables on three sides of the house, natural convection works nearly as well as the fan did.
So my conclusion is that you have a better chance at getting good convection from your soffit-ridge vent system just the way it's intended to work, without fans or gable vents.
Hudson Vall,
Interesting observation on the gable vents. I too have 3 and just re-roofed with metal. I haven't put the ridge cap on and was considering venting the ridge, although I really didn't want to cut through what is now a perfectly good roof. I also need to add more eave ventilation as they provided way to few. I think I'll wait on the ridge and see what happens after I add intakes at the eave.
Mark
I'd be interested to hear how that works for your house.
Check any sight on ridge venting and it states that there should never be any gable vents only soffiting vents.
Check any sight on ridge venting and it states that there should never be any gable vents only soffiting vents.
I'm sure that's correct but the house in question (post #7 from MS) has no ridge vent so he's interested to see how well its gable vents will work without them, once he increases the eave vents' efficiency.
I expect that he'll find that it won't change the attic space temperature very much but it's his opportunity to experiment with it.
If you can show him some figures that will help him make the decision about adding a ridge vent and eliminating the gable vents, goferit. I think he'd appreciate that kind of help.
Edited 7/16/2009 10:18 pm by Hudson Valley Carpenter
I see lots of good attic fan advice here, and that's great, but you should really be concerned about figuring out why your attic air exchange situation isn't working in it's present state before trying to fix it.
It is rare to find a house that absolutely needs electric ventilation (always because of poor design). I am going to assume your house is average and of decent to good design.
It is more than likely you will find that your soffit intake vent volume does not match your ridge vent exhaust volume. This is usually the case with houses with chopped up roofs and houses that use "cut in" soffit vents as opposed to "strip" vents. While I don't mind the perforated vinyl soffit vents I see so often, I would opt for something more substantial such as a continuous metal vent or poly-mesh/corrugated vent. I would also double check that those baffles are doing there job. Heat rises, so getting air out is easy...it's getting the air in that's usually the hard part, once you get that corrected, you can just let nature take it's course.
Post some pictures of your house (roof/soffit/attic) if you can.
DC
Ive attached a pic of 1) the house (faces south so lots of sun on the grey roof)
2) close up of a soffit which has a continuous vent the length of both eaves, the perforated vinyl type I believe, and
3) a gable view with now sealed off vent. I sealed both gables today, one on each end of house (east and west).When insulation was blown in Im thinking they put maybe 6 of the air flow tunnel things on each side of roof. Enough?
First of all those are gable "vents". They are way, way to small to have much of an affect one way or another.And unless their is solid sub-fascia blocking it you have continous soffit venting.Venting and insulation is not your problem. And I don't think that ceiling sealing is your problem. With 18" blown cels that will do a fair job of air sealing. And also blocking radiation.And not knowing anything other than it is a 2 story house with hot upstairs I will bet $5 that there are not high level returns in the 2nd floor and probably no returns at all.It is not so much the cold air falling as their is a hot air bubble formed in the 2nd floor that keeps blocks the cold air.The real fix is 2nd floor high wall returns. If you do have returns, but they are low you should be able to extend them without great expense. It might be much more difficult if their are not returns at all on the 2nd floor.My house is a perfect lab for this.I have 2 story build on a hillside. The garage and "main" entrance is 1/2 story above the 2nd floor. Right now (until next thursday) I have 2 separate HVAC one for each floor. But I only have AC on the 2nd floor. The first floor is slap on grade with a small amount of ground contact on the walls.It cooling loads show that it requires only has about 30% of the total cooling load.So with AC the first floor is warm, but it stays reasonable.The small landing at the main entrance 1/2 store above the 2nd floor has no return air and in the middle of the summer will get very hot.But it has the same open attic space as the 2nd floor, with the same insulation and ventilation..
William the Geezer, the sequel to Billy the Kid - Shoe
You get your roof replaced yet?http://www.quittintime.com/ View Image
No.I picked the contractor should have been ready to start in about 2 weeks.But I called to ask them to delay it until some other stuff gets done. They did not have a problem with that..
William the Geezer, the sequel to Billy the Kid - Shoe
"When insulation was blown in Im thinking they put maybe 6 of the air flow tunnel things on each side of roof. "
There is supposed to be one in every rafter bay... (or truss bay)
I'm thinking something else though... Did the house origionally have perforated vinyl soffits or was that material installed over old plywood soffits? If that is the case, I wonder how much ventilation there is in the old soffits that were covered up?
Also, I'd look into the staple up radiant barrier.
For attic ventilation it is always better to go with passive means if at all possible. One less thing to use energy and breakdown or need maintenance.
There is a 4" - 6" channel cut the length of the eaves before they were capped with the perforated soffit material. Sounds like I need to establish more/better airflow up from the soffits into main attic area....I guess I'll rake back the insulation and push the styrofoam air tunnels into each bay.
As you can tell, there are multiple answers to your problem!
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
Local plumbing, heating, and AC contractor has weekly radio show for a number of years. He starts off the show with a monologues before talking calls. Usually about something that he has seem during the week.This time he talked about this exact problem. He said that he things that 80% of the 2 story homes in this area have inadequate duct system to the 2nd floor. And often it is return issues..
William the Geezer, the sequel to Billy the Kid - Shoe
I didn't originally see the gable vents listed. That may be the problem. Air comes in the gable vents and short circuits right back out of the ridge vent. Try closing the gable vents so the risge vent can pull from the soffit vents.
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I'm going with a different angle here. I'll bet your house has a big open stairway to the upstairs. Cold air falls, hot air rises. I'll bet your thermostat is downstairs too. Nice big puddle of cold air downstairs, and no way to keep it upstairs.
Two thoughts:
1. Put a small fan in the stairway that will pull out all the heat from the house that is rising upstairs, send it on it's merry way.
2. Run the fan continuously so it keeps the cold air circulating throught the house. Force the air to circulate so it doesn't puddle where you don't want it!
Tu stultus es
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
Now thats creepy -- you're spot on. Where should I station a fan, downstairs or up? I'll also try running the blower continuously. However, the ceilings are still warm in the upstairs....
I would suggest a fan upstairs, on a timer (say 1 hour) in a central location like a hallway or at the top of the stairway.
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
P,
I would try to block the radiant heat gain by installing a radiant barrier on the under sides of the rafters. It is amazing what a little layer of foil will do. No bubble junk just foil.
Is the blown insulation fiberglass or cellulose?
KK
Its cellulose.