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Old 01-26-2011, 08:30 AM   #1
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Blocking eave vents in attic OK?


I'm finishing our Walkup attic as a livable room. We have vents in our eaves (that have been blocked in the attic for many years) and recently added roof vents in the attic. I'm adding a ceiling about 2' down from the ridge. I see that it would normally be recommended to have spacers between the roof and insulation to allow the eave vents to blow up through the roof. My roof however is framed with old 2x4's that limit the insulation anyway. Is there an issue with fully blocking the eaves and NOT venting them up to the roof?
I'd also have a whole house fan in the attic ceiling.

Thanks

Tim

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Old 01-26-2011, 10:03 AM   #2
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Blocking eave vents in attic OK?


Bad idea blocking the vents. It will cause heat buildup in the Summer which will cause the sheathing and roofing to deteriorate more quickly. It will also make the area upstairs very hot. In the Winter, the warm air that gets through the leaks in the walls and ceilings will cause moisture to freeze on the cold surfaces.
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Old 01-26-2011, 10:55 AM   #3
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Blocking eave vents in attic OK?


Stole this picture from a similar thread back in September.

Air has to flow, the ridge vent is worthless if the attic does not intake air from someplace else. Heat build up in the attic room is one symptom, but the most effected will be shingle life and the utility bill.







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Old 01-26-2011, 12:06 PM   #4
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Blocking eave vents in attic OK?


I am far from an expert. But i can tell you from experience that you will have moisture issues which will in turn mold your sheathing and later mess up your roof shingles. I caught mine before my shingles or plywood warped but i have mold on some of the sheathing and rafters. Not fun.
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Old 01-26-2011, 12:12 PM   #5
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Blocking eave vents in attic OK?


I've seen that vent product, but my roof rafters are barely 3 1/2" deep, so there would be no room left for insulation (between the knee-wall and ceiling anyway). The space BETWEEN rafters is often narrower than that as well. One other thought was to add roof vents behind the knee-wall so that whole area would flow. As I said, I'm adding a whole house fan to the ceiling so I'm not as worried about venting at the ridge.

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Originally Posted by dtsman View Post
Stole this picture from a similar thread back in September.

Air has to flow, the ridge vent is worthless if the attic does not intake air from someplace else. Heat build up in the attic room is one symptom, but the most effected will be shingle life and the utility bill.







Bo

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Old 01-26-2011, 01:53 PM   #6
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Blocking eave vents in attic OK?


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Originally Posted by timsplace View Post
I've seen that vent product, but my roof rafters are barely 3 1/2" deep, so there would be no room left for insulation (between the knee-wall and ceiling anyway). The space BETWEEN rafters is often narrower than that as well. One other thought was to add roof vents behind the knee-wall so that whole area would flow. As I said, I'm adding a whole house fan to the ceiling so I'm not as worried about venting at the ridge.
Your rafters will not pass inspections that way. To do it the right way your supposed to fir them out to have the proper size insulation. Do you have permits?
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Old 01-26-2011, 02:11 PM   #7
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Blocking eave vents in attic OK?


"As I said, I'm adding a whole house fan to the ceiling so I'm not as worried about venting at the ridge."
I don't know if you meant attic fan or whole house fan, but neither takes the place of a convective air flow system.
The whole house fan is used to cool the house. When it runs, and that's seasonal, it vents the attic as a by product of cooling the house.
If you meant an attic fan, they are mounted at the peak and are engineered to pull in cooler air at the eave line.
The other issue of 2x4 roof rafters shoud be increased so you can get the proper insulating value in there for your region.
You could help both issues by spraying in a closed cell foam directly on the underside of the roof sheathing.
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Old 01-26-2011, 02:27 PM   #8
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Blocking eave vents in attic OK?


As said before, you need to add framing to increase the space for insulation so you can bring that to code and add your vent chutes. The roof structure becomes another issue. You cannot just raise the ceiling height by moving the collar ties higher without first compensating either at the new ties or at the floor or both. I'm assuming you don"t have an architect or an engineer by your plan posted and I'd encourage you to consult one.
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Old 01-26-2011, 02:46 PM   #9
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Blocking eave vents in attic OK?


There are no collar ties in the construction now. This home is 105 years old (it's basically a 4 square). I'm adding a 8X18 ceiling and a knee-wall to an existing walk-up attic. There is very little structural impact to what I'm doing. But you've inspired me to have an architect friend come by to check out what I plan.

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As said before, you need to add framing to increase the space for insulation so you can bring that to code and add your vent chutes. The roof structure becomes another issue. You cannot just raise the ceiling height by moving the collar ties higher without first compensating either at the new ties or at the floor or both. I'm assuming you don"t have an architect or an engineer by your plan posted and I'd encourage you to consult one.
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Old 01-26-2011, 02:52 PM   #10
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Blocking eave vents in attic OK?


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Originally Posted by timsplace View Post
There are no collar ties in the construction now. This home is 105 years old (it's basically a 4 square). I'm adding a 8X18 ceiling and a knee-wall to an existing walk-up attic. There is very little structural impact to what I'm doing. But you've inspired me to have an architect friend come by to check out what I plan.
What size are the existing ceiling joists that you are now turning into floor joists?
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Old 01-26-2011, 02:59 PM   #11
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Blocking eave vents in attic OK?


They're 2x6's and the attic already had a floor (and alway's has).

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What size are the existing ceiling joists that you are now turning into floor joists?
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Old 01-26-2011, 03:02 PM   #12
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Blocking eave vents in attic OK?


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They're 2x6's and the attic already had a floor (and alway's has).
Just because it has a floor, doesn't necessarily mean it's structurally sound for living space.
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Old 01-26-2011, 03:08 PM   #13
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Blocking eave vents in attic OK?


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They're 2x6's and the attic already had a floor (and alway's has).
2x6's are ceiling joists and are not meant to be a floor. The plywood that's there is just for storage, it is not a floor. You obviously have no permits and didn't plan on getting permits and inspections. You are doing this illegally and nothing is structurally sound. What do you plan on doing about that? You CANNOT just finish off an attic.
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Old 01-26-2011, 05:39 PM   #14
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Blocking eave vents in attic OK?


Joe, I've got a professional carpenter (that does both commercial and residential construction) doing the work with me, and now (thanks to input from this forum) plan on having an architect consult as well.

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2x6's are ceiling joists and are not meant to be a floor. The plywood that's there is just for storage, it is not a floor. You obviously have no permits and didn't plan on getting permits and inspections. You are doing this illegally and nothing is structurally sound. What do you plan on doing about that? You CANNOT just finish off an attic.
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Old 01-26-2011, 06:37 PM   #15
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Blocking eave vents in attic OK?


It's always helpful to know what you'll be doing before you get there. The 2009 IRC may be the Code you are under, I would build to that minimum one for safety, at least. There are new requirements for attic rooms: http://docs.google.com/viewer?a=v&q=...1txlzU01V4JQIg

The 2x6 joists may work, depends on species, grade, on center spacing and span; http://publicecodes.citation.com/ico...002_par017.htm

Check with your local Building Department as to conditioned rafters (un-vented); http://publicecodes.citation.com/ico...006_par003.htm

Gary

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