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Old 02-08-2009, 03:00 PM   #1
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Attic ventilation question


I have heard, and seen in an online diagram that when installing Durovent foam ventilation channels between rafters, I should leave about a 1"-1 1/2" gap between panels, to allow air from within the insulation to make it through to the channel and then to the ridge vent. Makes sense to me, but would like clarification before I finish out the space. Is that the recommended method? Leave a gap, or install them end to end or overlapping? Thanks in advance.

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Old 02-08-2009, 05:33 PM   #2
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Attic ventilation question


Duravent has the proper installation instruction on their website.
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Old 02-08-2009, 05:58 PM   #3
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Attic ventilation question


4' panels? how many in each bay are you using? how deep is your insulation?

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Old 02-09-2009, 07:45 AM   #4
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Attic ventilation question


You only need a long enough panel to reach past the depth of your insulation. Durovent channels only prevent insulation from touching the underside of the roof sheathing and from blocking your soffit vents. You would need to have some serious depth of insulation or an extremely low pitched roof to have a need to butt two of them together. The channels are not meant to act as any kind of insulation.
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Old 02-09-2009, 08:20 AM   #5
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Attic ventilation question


what he said too.
i had 18/20 inches blown in over the new dining room, and the roof is 12/4 pitch. i used single 4' in each bay. i told them if the cellulose covered my baffles, i'd grab the leaf blower in the spring and clear them from the outside. i have not climbed up there yet to check though.

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Old 02-09-2009, 10:38 AM   #6
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Attic ventilation question


You need a gap between panels to allow any moisture picked up by the insulation to escape. Since the Duravent panels do not transmit moisture you need the gaps. If you haven't installed the roof deck, Tyvek AtticWrap is a better product in my opinion as it allows the insulation to breathe, it acts a rain barrier for when the roof fails and acts as an air barrier to make your insulation more effective.
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Old 02-09-2009, 10:50 PM   #7
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Attic ventilation question


Not sure I understand what difference the depth of the insulation makes. For what it's worth, it will be an R-30. (Crappy part is, I have to extend the depth of my 2x8 rafters, which are 12" o.c., with 2x3's to get enough depth to do the R-30). Anyway, as I understand it, the channels should run one panel width per rafter "bay", starting from just past the kneewall header, just above the soffit vent of a small continuous eave, up to the ridge vent. Sounds like I do need a gap between the panels to vent moisture within the insulation up to the ridge vent. Roof is already on, so can't use any other product really. I appreciate the feedback. Thanks again

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Old 02-10-2009, 12:16 AM   #8
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Attic ventilation question


When I installed the baffles in my attic, at first I did one full-length baffle in each bay. Then I measured from the upper open end of a baffle and down to the top of the existing batt insulation that's laying between the bays. If I remember right, there was only a 14" space. I want to put in 16" of blown-in cellulose. So I added 1/2 of a baffle to the end of all of the full-length baffles - the ends are overlapped. I also did it because, never having done this job before, the chances of me NOT shooting a bunch of that stuff down the end of the baffle are pretty slim. Hopefully, the added length will make the job a little less stressful.

Tpagel, do you live in a warmer part of the country where you only need R-30? Since you're extending the depth of the 2x8's, I'm guessing that you're adding batt insulation, but can't the top of the insulation be higher than the 2x8's? I don't know the answer to that, I'm just wondering.

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Not sure I understand what difference the depth of the insulation makes.
The deeper the insulation, the higher the R-factor.

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You need a gap between panels to allow any moisture picked up by the insulation to escape.
P.R. do you mean a gap between the panels from side-to-side or end-to-end?
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Old 02-10-2009, 12:27 AM   #9
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Attic ventilation question


I think I left out some vital info. The attic is being finished out as a loft space, so the insulation will go along the 2x8 rafters, not between the attic floor joists. I live in CT, and "really" should go with R-38, but since my headroom is at a premium, I don't want to extend the 2x8 rafter down so there is a full 12" of depth. I would probably have to sister a member onto the side of each rafter in that case, because I couldn't very well extend off the edge the additional 4.75". So I am tacking on 2x3's, for a depth of 9.75", and going with R-30.
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Old 02-10-2009, 06:38 AM   #10
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Attic ventilation question


Here's a useful site for info before insulating attics.www.buildingscience.com

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