How to Solve this Ventilation Puzzle

I have a 1 1/2 story Craftsman house with gable vents on the West and East side dormers. However, on the North and South ends of the house, there are no gable vents. If you were on the roof looking down, you would see two ridge lines forming a large “+” shape. See the attached picture of the house:

https://lh5.googleusercontent.com/-VkveoPgLmZw/TfaBAAS-TfI/AAAAAAAAAEU/D3_n6L7jb4A/s144/house.jpg

In the above picture, you are viewing the South side of the house. The house is made of brick (except for the East and West dormers which have steel siding. Again, there are gable vents on the east and west side dormers. The gable vents are the only ventilation in the attic. There are no soffit vents and no ridge vents. Complicating the installation of soffit vents are the following facts: 1) There is already 16 inches of insulation throughout the attic. 2) There are knee walls that would theoretically block any soffit vents at the bottom of the roof.

I am in the process of re-shingling my house. Now, it is my understanding that it is considered bad design to have a ridge vent when combined with gable vents because air coming in the gable vent immediately gets sucked up through the ridge vent.

Due to the placement of my two gable vents, I’m guessing that I have some degree of air flow through the east-west line of the house. But I’m guessing that I have very little air flow across the north-sourth line. Other than cutting through the brick wall on the north/south ends to install gable vents there, what would be the ideal way to ventilate the North and South ends of the attic? Could I get away with installing a ridge vent on the north-south ridge of the house? Would this get around the problem of ridge vents combined with gable vents, or would I still have the same problem? Hope this makes sense.

Thanks,
Bryan

Hi Bryan,

For a ridge vent to work it must have more soffit ventilation than ridge ventilation. If you can not add soffit vents then forget about the ridge. Your best bet might be to go ahead and go trough the wall and add gable vents at the North and South ends of the house.

PS the picture is kind of small but it looks like you might need to trim that tree off the roof.

JW


Miami Roofing

Darn. I was afraid you might say that. Is that my only other option? Could I install a powered vent or roof louvers on the North/South ends?

[quote=“JWRoofsMiami”]the picture is kind of small but it looks like you might need to trim that tree off the roof.
[/quote]

https://picasaweb.google.com/lh/photo/ROxly5USC14k1inSiZqnoAKtb4hnAg9OM3L6l7IZ468?feat=directlink

The picture is deceptive. It isn’t as close as it looks.

Thanks,
Bryan

Is that a finished upstairs or just open attic?

I take it that the “knee walls” are covered framing. I would take them down to the studs, so air can travel through them.

Then, I’d install a ton of soffit vents (# depending on the size of the home and soffit size), making sure they are not covered by insulation. You can make baffles to ensure clean air into the attic.

I’d put in a few turbines (not ridge vent for me), exact number depending on the size of the home.

I’d most likely cover the gable vents entirely, if the turbine/soffit vent process was working good.

It’s a hot, dirty job; but it is relatively easy for a DIYer.

If your attic space is open, without knowing more explicit details I would say your easiest option is to place a gable fan in one of your already existing gable vents:

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It’s not optimal but will upgrade your ventilation with minimal effort. If however you want to do what is technically right or are concerned with ice damming issues you will need to clear an air space from soffit to ridge area, close off the existing gable vents and run a quality ridge vent (like GAF Snow Country) on the entire ridge and install a soffit vent (we like Ever-Flo Inhaler™). Obviously this is considerably more effort from what you’ve said. If you live in a high snow area it’s probably worth the extra time and money to do a text book ventilation install. If you live in a low snow area I’d probably opt for the easier (but less efficient) gable fan and be done with it.