I just need to vent
June 26, 2011 5:47 PM   Subscribe

[Attic Ventilation Filter] Is it worth the money to add a ridge vent to my roof? I currently have a two-story house with an attic, which is ventilated with soffit and gable vents. Twist: I'm getting a new metal roof.

One of the gable vents has a fan attached, which automatically comes on at a set temperature. I've seen this question, which suggests blocking the gable vents is good if you have a ridge vent. But knowing that my new metal roof will keep things cooler in the attic, and that I have a presumably functional, though perhaps not optimal, system in place, will adding a ridge vent be worth some extra money? Or should I take a pass on it and save myself several hundred dollars?
posted by Shoggoth to Home & Garden (5 answers total) 2 users marked this as a favorite
I don't know the answer to your question, but just wanted to ask you to please keep an eye on your ventilator fan, and make sure it's well-maintained. The house I was living in recently burned down because of a short in the wiring in the ventilator fan, which caught the insulation on fire and spread through the house. The fan hadn't been inspected in over a year, which may or may not have made any difference.

I don't mean to scare you, and mine could be an unusual situation, but I thought I'd mention it just in case it could spare heartache in the future.
posted by odayoday at 5:59 PM on June 26, 2011

Warm air rises so depending on how high your gable vent is, the hottest air in your attic probably isn't being efficiently exhausted. The ridge vent/soffit combination is superior for this reason. However, it is more important in colder climates where there is snow accumulation and you don't want the snow on the top of your roof melting, running down your roof and freezing. That can lead to a leaky roof or chunks of ice sliding off. Properly ventilating your attic can cut down on cooling costs in the summer too, and keep it from approaching potentially dangerous temperatures.

The question you linked to only suggests to block the gable vent because air was not being drawn in through the soffits. If you do want to go with the ridge vent, make sure there is enough air intake from the soffits before blocking the gable vent. Ideally, all of your air comes in from the soffits and exits through the ridge vent. I don't know if it's worth it to you. That depends on your heating/cooling costs, size of your house and roof, and your climate. No one will know better than a local architect who specializes in custom homes though.
posted by comatose at 7:58 PM on June 26, 2011

I think you should consult with whomever is putting on the metal roof. There is something called (if my memory serves me) a Metal Roof Alliance. Here is a link; http://www.metalroofing.com/. I would suspect you'll get an appropriate answer there.
posted by chosemerveilleux at 6:29 AM on June 27, 2011

Best answer: Ah, that was my original question you linked to. I learned a lot about roof ventilation when I was working on it.

Ok, there's two things with the metal roof. First, you want to make sure that they fir out the attachment points for the metal roof so that you have an air channel between the new metal roof and your roof sheathing. It should be vented at both the soffits and the peaks and eliminates most of the need for attic ventilation in hot climates. After that, then you can get away with just a turbine or turtles that are rated for the number of cubic feet in your house. HOWEVER: You want to make sure that you only put the turtles or turbines on one side of your house. If you put them on both sides of your house, the air will just blow in one turtle and out the other turtle, similar to the problem I had with the ridge vent drawing out of the gable.

Most of the ridge vents on the market have that problem where wind blows straight through and doesn't actually draw... so unless you need a specific convection pattern the way I did, then you don't really want to do that. If you do, get a really high grade roll one like the AirVent ShingleVent II, which is designed with that deficiency in mind.

I would PERSONALLY get rid of the fan. They're known to start a lot of fires and it's personally not worth it to me when turbines offer an equivalent or superior volume of ventilation through convection alone.
posted by SpecialK at 3:09 PM on June 27, 2011

Response by poster: Thanks to everyone for the useful answers -- we can have a much more intelligent conversation with our roofer now. I think we'll definitely get rid of the power gable fan.
posted by Shoggoth at 7:10 AM on June 28, 2011

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