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I live in Seattle. It doesn't snow here often. Winters are cold, but temps do not dip below 32 for long periods of time very often.

I live in a small, one-level 950 sq. ft. house built in the 1950s. It does not have air conditioning.

I don't want to get air conditioning, but I do want my house to be more pleasant temperature-wise during the summer, so I'm trying to figure out how to ventilate my attic.

Right now there are two very small, screened vents under the eaves of my house. There are attic vents on the top of the roof, but none under the eaves. I understand this is a problem, and I've read a bit online that you have to have at least the same amount of airflow capacity at the top of the roof as you do under the eaves, and that the total airflow capacity at the top needs to be X amount based on the square footage. So I kind of get that.

I also know that vents have a net airflow capacity rating.

My problem is that I don't want to put in vents that bees and wasps can get into. Seems like every year they're in something new -- last year I had to get a new nest out of the wall, and before that, it was in the wooden steps in my front yard.

Makers of vents must not think that insects exist because when I look for under-eave vents at Home Depot, they're the grate kind with 1/4 inch gaps between metal slats. No bueno. So what under-eaves vents can I use to maximize airflow and minimize insect infiltration?

According to my calculations based off this site, for my 1000 sq ft. attic, I need a total vent area of 6.6 sq. feet, and a soffit vent area of 3.33 sq. ft.

Run of the mill vents like this one provide 92 sq. in. of vent area. This is .63 ft, which means I'd need 5 of them. But if I put netting in there, I'd likely need more. I'm asking if I put netting in there, how many more vents do I have to have?

  • I have seen some with really small screening attached to larger slats. That said, what size overall are you looking for? 12 inches by 20 feet, 5 inches by 8 inches, etc? – user20127 Mar 13 '15 at 23:54
  • See edits for more details. My soffits range between probably 16 and 24 inches wide. Beyond those limitations, and the need for 3.33 sq. feet of vent space, I don't care too much the size. – Trevor Mar 14 '15 at 0:10
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I live a couple of hours south of you. I installed a heat activated powered vent in the roof. Our house was miserable in the summer at night. You could feel the heat radiate from the ceiling. After adding the powered vent that turned on @100 deg F the house was comfortable in the evening. They have solar powered vents now , so power would not need to be run.
The powered vent was much cheaper than adding the vents at the soffits, and being close to the ridge it removed the hottest air.

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Almost any vent can be used in conjunction with insect screening. I suggest an aluminum or vinyl strip vent (3-4" wide), with metal screen installed immediately behind.

Assuming plywood soffit, rip a channel lengthwise a bit smaller than the vent covers, staple screen over the channel, and fasten the vent over the screen.

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