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please help with roof ventilation

986 views 13 replies 3 participants last post by  nemo77 
Assuming you get some cold weather in VA then you need to have ventilation during the winter as well as during the summer. In winter you are removing moisture that leaks into the attic where it can condense on the bottom of the roof as well as excess heat which can cause ice dams. The temperature controlled fan will not be operating in the cold weather.

Not sure what they are proposing for their $800 soffit vent install or what you have for soffits. The NFA (Net Free Area) you would want to add for the soffit vents would be around 2.5 ft². You would also want the same amount for high vents NFA with gable vents and a ridge vent. More on that if you would like.

Give us some details on what they were proposing for those soffit vents and what your soffits are made of.

Bud
 
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Two 18 x 24 gable vents at 50% NFA gives you about 3 ft² of vent area, which is good.
The metal covering your soffits can be a pain to remove and since the metal needs to be cut as well it might be possible to cut through both at the same time. An option where I would need to see to consider. Not sure if the new vents can be sealed to the soffits that way. Back up here for a second. Again I'm not sure what you have, but if those metal soffits can be replaced with vented vinyl soffit material then the job might be a lot easier. Some pictures might help.

However, what you have seems to be working and your moisture issues are not as bad as what we face here in the north country. If you currently are experiencing no mold or mildew issues in the attic then the soffit vents may be able to wait, especially at $800. When you replace the roof and add a ridge vent, then you can consider retiring the powered exhaust and going with natural ventilation. In any case the air sealing of the attic floor (ceiling below) should be done and your insulation should be at least code minimum.

Almost forgot. Attic floor area divided by 150 gives you your total NFA. With just ridge and gable vents there is not a lot of height difference and it is the height that helps to create the air flow. Gables will work with a ridge but may need a breeze to help. Unknown how well, but soffit vents can be added at any time.

Bud
 
Did they install baffles in every rafter channel?

With no history and some comments that you have moisture issues and lacking a history being new to you, definitely add the soffit vents.

However, nix the $800 estimate. Vinyl soffits often snap out easily. Someone then cuts some holes or slots. I used a hole saw and cut between pairs to provide longer slots at each rafter channel. Then install the perforated vinyl soffit. Even if this is a 2 story home, they will be done in half a day. Pictures will help with that opinion. Get some more bids.

Busy building season so they often bid high to make adding someone to their list worth while. You might talk to the roofing company as some get involved with trim and minor work like you need. They will also have their people and equipment on site so a couple hundred extra would be gravy.

Bud

Just wanted to add, if the roofing company insists or recommends you close off the gable vents when a ridge vent is added, don't do it. The explanation is a bit long but glad to go over it as the excuses they use are not valid. They sound good, but wrong.
 
This project is getting easier all the time. Looks like you already have perforated soffits, just need some holes above. For the guys who work off of a ladder (not me) that is a piece of cake. Pop out 3 or 4 panels, a bunch of drilling and pop them back in. Move the ladder and repeat. One guy, 3 hours, and no materials, $300 and he has a good days pay. And you get to keep the other $500.

I've been trying to correct the roofing industry for several years and some have changed. But the problem with their reasoning for removing the gable vents is, gable vents or not, it doesn't reduce the pressure across the soffits. Air moves due to a pressure difference and a path. Leaving the gable vents in place actually increases the pressure across the soffits. All of their other arguments about short circuiting are just a smoke screen. They say air follows the path of least resistance, ya, but only if two paths have the same pressure difference pointing in the same direction. The pressure across the gable vents is pointing out.

There are reasons to close off the gable vents, rain and snow being two. but yours have been in place for years and you see not issue. besides, if a problem came up, very doubtful, later on, they can easily be covered on the inside at no cost.

Bud
 
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