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Need better attic ventilation WITHOUT soffit vents

Need better attic ventilation WITHOUT soffit vents

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  #1  
Old 09-13-12, 12:41 PM
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Question Need better attic ventilation WITHOUT soffit vents

I have a cape cod built in 1941 that has no soffit venting around the bottom of the roof, what I do have are two gable vents front and back of the house, and two poorly placed box vents. Assuming it is impossible or prohibitively expensive to try to add soffit venting (because there is VERY little space under eves for installation of said venting), what are my best options for ventilating this space? I should add that I have a lot of rusty roof nails poking through in the attic so I may have a moisture issue, ice damning is not too bad. I live in upstate NY. Will adding several more box vents help? Should I consider a thermostat/humidistat power fan? I have heard conflicting things about these fans. Any help would be much appreciated. Thanks.
 
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Old 09-13-12, 02:25 PM
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Welcome to the forums! Not sure what a box vent is, but if it is mounted on the roof, it probably is fighting with the gable vents. On Capes, gable venting is about as good as it gets. I would not add anything, motorized, thermostatically controlled, etc. to the roof. Why punch a hole in a roof that wasn't leaking in the first place? Ensure your gable vents are open and sized correctly, and you can possibly add a thermostatically controlled fan on one of them. That will create a cross breeze that could help with moisture and heated air movement.
 
  #3  
Old 09-13-12, 07:56 PM
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attic ventilation for cape

Thanks, Chandler. Honestly, I just wish I would get the same opinion from two people. I've asked a bunch of roofers and several insulation contractors and each says something slightly different about using different combinations of venting from ridge vent, to box vents, to powered fans, to bigger gable vents, to insisting I try to cut in soffit venting. Totally confused. I'm about to get a new roof and I just want to ensure that crappy ventilation, moisture, etc. doesn't compromise any of the new roofing material and shorten the lifespan of a very expensive roof.
 
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Old 09-14-12, 03:42 AM
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I agree. Opinions are like bellybuttons. Everyone has one. Think through it from your houses' standpoint. Remember we can't see it. You want to move air effectively. If you impede that movement, you are causing vortices and stale air in parts of the attic. Your worst enemy is the beauty of the house.....no soffiting. Cutting holes in your roof will cause any air movement across your gables to extract air from the source of least resistance, and it could quite possibly be the roof vent holes, leaving moister stagnant air at the bottom along your insulation. You want to move the air without interruption from one gable to the other, hence my suggestion of the gable fan on one end. Much of the information you are getting is localized, so it would be more apt to work in your climate, so don't disregard any of it. You'll just need to arrive at a point of decision. Look around in your neighborhood and see what they have on their Capes.
 
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Old 09-14-12, 06:55 AM
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Hi mcrupi and another welcome to the forum,
You are correct that there are many varied opinions, especially on this very simple issue. I'll ask Larry (Chandler) and all to forgive me in advance, but I have another slightly different opinion.

Being an energy auditor I found it disturbing that much of the advice out there seemed to be simply repeating what they had read or heard with no science or research behind it, not that the science and research always agree. But my search was successful and I now have a much better understanding about how air moves through our homes and attics. I'll try to give you just the relevant parts.

Air moves through an attic by convection (we call it stack effect), wind, or mechanical help such as a fan.

The fan: They are very effective at moving air, but they can also draw air from the house through all of the leaks that are currently allowing that moisture you see evidence of. Regardless of what approach you take, especially the fan, you need to seal off as much of that air leakage as possible. This link will help: http://www.efficiencyvermont.com/ste...ide_062507.pdf

The wind: Every house will be different. Local winds, orientation, exposure (trees & buildings), style, and venting. But unless you live on a hill with a steady breeze, the wind may not be enough and we have to be careful with the wind when building as it can also carry snow and moisture with it.

Stack effect: This is the natural air flow created by a different temperature inside vs outside and is perhaps the most common, but it requires vent area and a difference between the height of the intake and the exhaust (as well as a temperature difference). Two vents at the same height will have essentially the same air pressure thus little air flow. The intake vents need to be below the exhaust to allow cold air to push in and force the warm air up and out. Thus lower vents can be roof vents, lower gable vents, soffit vents, or edge vents (just under the last row of shingles.

Since you are installing a new roof, your timing is perfect. My initial thoughts would be, definitely add the ridge vent. It would take the high position. If the gable and current roof vents are high as well, then steps should be taken to add some low venting, lower gable, lower roof vents, or even ducting the current gable vents to a lower inside height (it works).

I'll stop here, but start with the air sealing (plus insulation) and review your vent options. Recommended vent area is one ft² net free vent area for every 150 to 300 ft² of attic floor. You need to include the area of any slopes.

Bud
 
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Old 09-14-12, 01:31 PM
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Bud, no apologies needed. I wholeheartedly agree with ridge venting, as you know from previous postings. Getting the air to the ridge would be the trick. I am unsure how low venting on the roof would work on a Cape, as I have never built a house without soffits. That would increase convection in the right direction, from low to high. I mentioned the existing gables because......well they were there.
So you see Mcrupi, there are more opinions and all have their attributes. Sadly to say, you are the one to decide.
 
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Old 09-16-12, 07:05 PM
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Not sure what a box vent is, but if it is mounted on the roof, it probably is fighting with the gable vents.
aka a "turtle vent." Or "a hole in an otherwise perfectly good roof." And yes, they would fight with the gable vents.
 
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Old 09-16-12, 07:28 PM
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If the OP cuts in soffits vents he will be letting cold winter air into the living area upstairs. It may be fine for the summer but not for the winter.

I too have only gable vents on my 1950 cape. All I did was add a ridge vent when the new roof was installed. I left both gables as they were.

The way to do the capes is to add the baffles between the roof (trusses?) and reinsulate. Then cut in the soffit vents, ridge vent and close up the gables. I was not gutting my upstairs to do that...LOL And noway was I cutting soffit vents to an already under insulated and cold 2nd floor in a cape. Hot in the summer and cold in the winter...Uggg
 
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Old 09-16-12, 07:54 PM
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there is VERY little space under eves for installation of [soffit] venting
But you do have some overhang, it sounds like. Another member here, who has no soffits on his house, recently installed intake vents by creating a space at the top of the fascia boards between the rafter tails. There might be ways to do it.
 
  #10  
Old 09-25-12, 10:26 AM
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attic vent without soffits

I have a Colonial Style House built in 1953. The attic is 1080 sq/ft there are no soffits or soffit vents. On one end there are a pair of gable vents built around a brick chimney stack. And on the other ends (L shaped) 1 small window and nothing else. On the end with the gable vent is also a whole house fan. The roof was built without much or any of a soffit (so adding soffit vents will be impossible).

I recently completed a home energy upgrade to achieve at least a 25% gain in energy efficiency through, new AC, heater, hot water heater and more attic insulation and and air sealing. There were existing bats of fiberglass under the attic floor board but more than 4" of cellulose was blown in under the boards and all the boards and and edges were air sealed. I can feel the difference. I think the old system relied on the house being leaky for the gable vents to work with the stack effect.

Now that the attic is air sealed from the res of the house where can I add vents to keep the house from burning the attic and roof? Should I add a thermostat controlled fan and duct the gable vents?
 
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Old 09-25-12, 01:12 PM
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Gable vents were designed to work autonomously without any help. Your old system was not relying on any air escaping from the house to work properly. Your house was leaking and was not efficient. Keep in mind, your living space and the attic space are to be treated as two separate areas, sealed from each other.

If it makes you feel warm and fuzzy, then adding a gable vent fan with a thermostatic control will help keep the heat at bay. And, I am not sure what you mean by "duct" the gables. Leave them alone, attach the fan to one and let it run.
 
  #12  
Old 09-25-12, 03:49 PM
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I would replace the small window with a louvered vent and control the fan with a humidistat. The purpose of attic ventilation is not to cool your attic. It's to vent moisture out to keep your insulation dry and effective, prevent mold, and reduce or prevent icing.

As I said earlier, another member here has successfully added intake vents to his house, which has no soffits. Pictures of what you have would help us to see your situation. See How To Put Pictures In Your Post.
 
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