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I have read a lot about proper insulation and ventilation, including some posts on this site, but none adequately answer my questions.

My goal is to operate an electric heat source in the winter and have ~60 °F temperature maintained when working in the garage. In the summer, I think we will typically leave the garage door open, however it would be nice to one day have it stay cool in there if it's 90-100 °F outside.

This is in Ohio, where we typically have temps of 0-95 °F throughout the year, it can also get pretty humid.

I do not have soffit vents, but there is a ridge vent on the roof already installed. I do not want to drywall nor do I want to build a ceiling.

As you see in the photos I have already insulated the walls with R15 Batt installation. Now I'm unsure where to go from here for roof 2x6's. I bought some radiant barrier R11-equivelent insulation (seen in photos as well), which I was planning to attach to the end of the 2x6's above, which leaves plenty of ventilation behind them, should be "ok" in the winter and pretty decent in the summer. However, not having soffit vents, I'm unsure if that is the proper use-case.

You'll see from the wall install that I have no concerns about a vapor barrier, and do not care to seal my garage 100% (I only got faced insulation because it was cheaper =) ). However, I am concerned about mold/moisture problems in the space.

I would love some feedback as to the proper way to proceed here. Ideally I can make use of my radiant barriers, and ideally I won't have to cut in soffit vents.

Full resolution images here for reference: https://i.stack.imgur.com/Aej0Q.jpg and https://i.stack.imgur.com/gXKeH.jpg

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  • You should show a picture of what the outside construction looks like at the rafter tails and between them. It could be that your resistance to putting in soffit vents may be legitimate but depending upon how the eve area is built it could be an easy job to add some vents. And if you had those vents you would have the options for a far superior ways to insulate the rafters from below on the inside.
    – Michael Karas ♦
    Feb 20, 2016 at 19:28
  • @MichaelKaras I've added additional images from the outside as requested. I actually think that I can cut into the white material closer to the garage (not the gutter of course) and it would come up perfectly inside ... I'm more just trying to see if I can get away with not doing that for the sake of the extra work on it is all (i.e. is it REQUIRED for proper moisture control?). Thanks.
    – Shackrock
    Feb 20, 2016 at 20:43
  • The issue of moisture control is that there needs to be free air flow on both sides of a vapor barrier so that any dampness can dry out. You also want to try to keep any vapor barrier so that it does not have a sharp temperature drop across it keep it from inviting condensation on the warm side. Opening vents in the soffit would allow air to flow from the low edge of the roof up along each channel between the rafters and up to your ridge vent. This allows you to put insulation on the bottom side of the rafters but allows outside temperature air to circulate under the roof (continued)
    – Michael Karas ♦
    Feb 20, 2016 at 23:18
  • (continued from above) surface and helps prevent ice buildup on the roof when there is standing snow on the roof. The soffit vents in that space behind the gutter would be useful only if that space is open to the inside over the top plate between each rafter. Construction is typically like that but you should check that.
    – Michael Karas ♦
    Feb 20, 2016 at 23:24
  • By the way soffit vents could be as simple as a series of say 1.25 to 1.5 inch diameter holes drilled up into each rafter tail cavity and then covered with a mesh screen. They make ready made screens that have aluminum frames that can simply be screwed or stapled up over the series of drilled holes to prevent insects and other critters from going in the holes.
    – Michael Karas ♦
    Feb 20, 2016 at 23:31

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Well, it's a good idea but why not care about re-sale & do it right by drywalling everything & install some outlets & add more lighting? The R-11 is okay, but I'd even go with at least foam boards on top of the rafter ties. Hot air does go up & in the summer without vents it will radiate down.

Absolutely put in gable vents or at the very least drill 200 small holes in a rectangular pattern in each gable...angled down if drilling from the inside or angled up if drilling from the outside, to keep water out.

Finally, you'll want to insulate the garage door with foam board & make sure the entire door's perimeter is sealed. What I'm saying is that 1 major weak point will ruin the idea of ever being comfortable.

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