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What do the energy pros do here in the corner of a hip roof? I don't have enough room to install a baffle. I want to install insulation here, so I'm not sure if I would run into problems with moisture if I were to just block off the air space between roof and wall sheathing

corner area

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First off let me say that I am not a professional insulation installer. But I can tell you that the idea with baffling is that it is supposed to allow a space for air to flow from the soffit along under the roof sheathing to the open air space above the insulation fill level. From looking at the baffle that that you have installed so far (along area in the red box below) it looks like the baffle goes all the way up to the hip rafter.

I believe that you will need to work out an air channel along the hip rafter in these short stub rafter openings that allows for air flow. Since this may well span across several of the stub rafter openings before it gets above the insulation fill level that channel will have to be able to be lower than the bottom of the stub rafter upper chord so as to allow air flow from the lower level opening to the next higher opening. Such air channel would have to be done along both sides of the hip rafter. Once this channel is provided for it can be extended down to the openings I have shown in the yellow ovals.

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You may be able to then reach into these corner openings and put some baffle material but it would need to low enough down that the upper portions of the openings in the yellow ovals are open. Alternatively it may just be easier to hand pack the insulation in those corner spaces and just not allow it to fill over top of these openings.

  • Indeed the baffle that I cut at an angle needs to be cut back more. I just did that to get it to fit in there. When I moved over to the corner I realized that would be nearly impossible to cut the baffle to fit for that corner and have it do any good. I really don't understand how the professionals would install a baffle here. If I have 12 inches of insulation, where would I be able to vent that corner? If I block off the venting in the corners of my roof, will that be a problem? – Nic Oct 27 '15 at 19:56
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    @Nic - Ideally I think you want to find a happy medium of insulation in those corners and air space that will circulate to the area above the insulation fill level in the greater part of the attic space. If that means that you get 8.5 inches of hand placed insulation in those corner pockets but at the same time have vented the corners along the hip rafter as I described in my answer you have done a good enough job. Note that all of this discussion is moot if you do not have soffit venting to the area under this last pair of rafter tails. – Michael Karas Oct 28 '15 at 4:15
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Since it's difficult to vent the lower portion of a hip roof, they usually aren't. Ridge vents typically aren't intended to be used on hips (though some are now available that meet the unique weather-protection needs of sloped ridges). You can simply remove the baffles in that area and fill your space with insulation.

Some might suggest leaving an air gap, but that necessarily reduces insulation, which would probably lead to a more severe ice dam problem. I'd seek a ridge vent that is designed for sloped ridges, or simply fill the space and move on.

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