Is this enough venting

2232 Views 2 Replies 3 Participants Last post by Gary in WA, Jun 12, 2011

dntsdad

Discussion Starter · Jun 10, 2011

My house is hot as heck inside and I am thinking that it has to do with the attic area not having enough venting. I am not sure on the exact temps but it is usually a good 30degrees warmer in the attic than outside. Black shingles are not helping but thats what I have.

Here is an birdseye view of my house.

All I have for venting is the ridge vent that runs next to the AC unit and across the garage. There is NOTHING else. There is a total of 54ft. of vent.

Anyone think that this in enough??

I also have the eve vents to allow air in shown here. A total of 5 of them around the house.

I need to do SOMETHING to evacuate this hot air as I am hoping that this will help the house stay cooler. It is routinely 100+ until late September and $700 per month electricity bills are not sounding good.

I have been looking at the power vents that mount on top of the roof and was thinking of putting it somewhere by the AC unit. I have read though that this may not work as I will suck air from the ridge vents and thus create now real air flow and evacuation.

My next bright idea is this.

This is my garage standing at the big door. You can see the drop down ladder I have to gain access to the attic for storage.

There is drywall separating the garage crawl space and the space above the house. However, I made a hole to provide easier access to the house space when I was running wires and such a long time ago.

I was thinking of installing a gable fan or maybe a whole house fan in the garage to keep the noise out of the house that would blow into the garage space and thus into the house space and then vent out through the ridge vents and evacuate the hot air.

Either of these plans, the fan in the garage or the powered vent on the roof, seem like they may work? If so, which is the better plan of attack?

Thanks VERY much for any help in advance.

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Grumpy

· #2 · Jun 10, 2011

I did not run the numbers. I could if you like. At first glance, I would say, no, you do not have enough venting. I seldom ever put ridge vent on a hip roof. In most cases the ridge lines are too short. In your case, it's border line by eye ball. Again i did not run the numbers. I could also run the numbers on the intake, but damn I am tired, I woke up at 4:30 am, however also at first glance I would say the intake is inadequate. When you have 2" intake I usually want to see it continuous on all sides. Your intake obviously starts and stops.

While the goal is to keep the attic as close to the outside temprature as possible, I have never been in an attic that wasn't warmer than the outside. Even with exceptional ventilation you should expect the attic to be a little warmer than outside.

You may look into better attic insulation. As well, a friend of mine just installed radiant barrier and promised to keep me posted ont he results but expects his attic temprature to drop signifigantly.

If you do install power vents you will need more than one, and should remove the ridge vents. Either way I would highly highly recommend continuous intake all around the drip overhangs.

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Gary in WA

· #3 · Jun 12, 2011

38x55= 2090 + 22x20= 440 = 2530/150 (without a v.b.) = 17 NFVA

½ of 17= 8.5NFVA in soffits + ½ of 17= 8.5 in pot vents (turtle-backs)exhaust

8.5 x 144= 1224 sq.in. NFVA / continuous soffit @ 9NFVA = 136 lineal feet http://www.airvent.com/homeowner/products/intakeSoffit-specs.shtml

Grumpy was right-on, hope he got some rest......

38 + 55 +38 + 35 = 166 because garage drywall goes up last garage common truss. Drywall the hole in the fire-wall at garage/house attic or a fire-door.

Use pot vents to total 166NFVA, same as soffits. Continuous at the garage soffits, both sides.

Gary

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