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Old 08-10-2012, 11:06 PM   #1
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venting with no horizontal roof line


trying to figure out how vent a roof that has no horizontal lines. dont even know what you would call this type of roof but i will try. roof has no horizontal plane. therefore have no place to put any kind of intake for roof venting. roof is basically a gable connecting to another gable at low point. slice and layed flat would be an upside down ww. building an room upstairs but needing help on ideas for venting what i can think of is maybe powered vents on top with maybe a single hole cut in side of house to provide intake? i dont think ridge cap would work due to not enough intake? any help? before the roof was vented with gable vents but after installing kick walls for addition trying to figure out how to draw air from behind kick walls and vent.


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Old 08-11-2012, 12:41 AM   #2
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venting with no horizontal roof line


You can see the roof, no one here can without a picture.

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Old 08-11-2012, 10:08 AM   #3
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venting with no horizontal roof line


+1

Post up a picture if you can. It will get you a bunch more feedback.
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Old 08-12-2012, 04:08 PM   #4
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venting with no horizontal roof line


Any ideas
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Old 08-12-2012, 08:44 PM   #5
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venting with no horizontal roof line


I see lots of places to install ridge vent, for a far better look on that house you could also add soffit vents and get rid of those exposted rafter tails at the same time.
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Old 08-12-2012, 09:22 PM   #6
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venting with no horizontal roof line


Yes room but if over half of the soffit vents are above the kick wall and also at the same height as the ridge vent won't those just short circuit the ridge vent and only pull air from the shortest distance leaving kick wall and below unvented
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Old 08-13-2012, 10:36 AM   #7
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venting with no horizontal roof line


Is that window in the attic space?
Is there another one on the other side?
Why is the subject of venting being raised?
Do you have moisture problems?
Do you have excessive heat problems?
Has someone simply told you its needed?
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Old 08-13-2012, 11:03 AM   #8
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venting with no horizontal roof line


Yes Window no on other side. The upstairs is finished and having moisture problem behind kick walls. I also additional info room has a dropped ceiling about 3 feet down from ridge
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Old 08-13-2012, 11:42 AM   #9
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venting with no horizontal roof line


How is the roof framed? Is a single straight ridge gable roof with two side gables overframed? or is a true frame gable where you if you stand in the middle are the four gables wide open on the inside?

Problem becomes with a true frame that all of the rafter bays terminate into the valley beams. There is no place to allow air to enter and follow the rafter bay to the ridge. If you're having problems in the crawl spaces you'll probably be looking at louvers on the exposed side walls and possibly even a mechanical fan of sorts to ensure proper ventilation.

The other option, but way more $ than the louver/fan noted above, is to replace your roof (shingles) with a ventilated system. If you're interior insulation is good, then you only need to provide battens (2x4s) and another layer of plywood, and then shingles again. Here is an image generally showing the ventilation system. The 1x4 or 1x6 sheathing noted could easily become plywood. http://inspectapedia.com/BestPractices/Figure2-48.jpg
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Old 08-13-2012, 12:17 PM   #10
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venting with no horizontal roof line


Yes it is the true frame you mentioned when rafters terminate on valley and that in there lies the problem
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Old 08-13-2012, 12:35 PM   #11
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venting with no horizontal roof line


Quote:
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Yes it is the true frame you mentioned
Then you're looking at one of the two options I noted...
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Old 08-13-2012, 12:53 PM   #12
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venting with no horizontal roof line


Couple of questions then. Would multiple smaller vents running across work better than say a single large vent on each side work better and then due to the fact that the rafters don't really run from peak to bottom what would my best bet be for exhaust. Ridge vent or a couple of mushrooms(power vents) close to peak
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Old 08-13-2012, 01:09 PM   #13
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venting with no horizontal roof line


It sounded to me like you were finishing, or had finished, the space off. If that's the case then you won't be getting much flow from the base to the ridge. The whole space would have to be left open and un-conditioned to allow for air travel from the intakes (louvers in side walls) to the exahust (ridge vents or mushrooms vents).

If the space is being finished then you'll need to ventilate each crawl space infividually. Taking into account the insulation envelope, air sealing, and air movement within each space. You'd need and intake and exhaust for each area, and if there is not room for at least a 3'-0" difference in elevation between the intake and exhaust then a mechanical fan would have to be introduced.

Or re-do your roof and introduce venting along the roof sheathing plane...
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Old 08-14-2012, 09:34 PM   #14
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venting with no horizontal roof line


You need to find the source of the moisture. Is your ceiling insulated and sealed properly? Do you have bathroom vents and are they vented directly to outside? I would concentrate my energy and dollars here first.

Adding ridge vents will not help and actually may hurt your cause. Ridge vents without adequately sized intake will create a negative pressure in the attic. This will in turn "steal" more air from the your house and can cause more moisture to leak into the attic. You really don't have much of any place to provide traditional intake.

If it really bothers you and want to provide some ventilation, then SmartVent or a similar type product may be a way to go. I have used their product a lot on eaves and ridges, but never in a valley.
http://www.dciproducts.com/html/smartvent_other.htm

Another way to handle this type of house would be to insulate the rafter bays and condition the entire attic or second floor. Would be costly.
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Old 08-15-2012, 09:04 AM   #15
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Quote:
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If it really bothers you and want to provide some ventilation, then SmartVent or a similar type product may be a way to go.
This product cannot be used here as the roof is a true frame gable system. The rafter bays all terminate into the vally beam.

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