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Reroofing question

E A | Posted in Energy Efficiency and Durability on

New member, Zone 3 (Orange County, CA)
Two-story home 2700 built in 1979

I think I have a good “reroof” plan for my house.  I’m trying to make it as energy efficient as possible while getting it ready for solar panels.  Below is some current info about the home, as well as my plans to reroof and insulate.  Can you experts please help me confirm if I am on the right track with my project – if not, please make suggestions?

Currently the home has a shake roof with exposed eaves – no soffit vents.  The house has two attics (att.1) 245 sqft and (att.2) 130 sqft.  Attic 1 is ventilated with a 24×30 gable vent; attic 2 is not ventilated.  The strange thing is the attics do not extend to both sides of the house.  I.e., both start from the south facing side, slope up to the ridge and are walled off after that.  The remainder of the home is cathedral ceiling following the slope of the roof which 12/5.  The cathedral ceiling is not ventilated either  There are no hips or valleys – it’s a pretty a simple angled roof.

New roof (std concrete tiles) and insulation will call for ventilating both attics, but not venting the cathedral ceiling…here’s what I plan to do:

1. Airseal the heck out of both attics and the cathedral ceiling space.
2. Add intake ventilation to the bottom slope of the roof above both attics using O’Hagin vents (again, I have no soffit vents and exposed eaves)
3. Add balanced number of O’Hagin vents for exhaust at the ridge (not using ridge vents – also not planning on sealing the attic 1 gable vent). 
4. Remove space sheathing during demo and install radiant barrier plywood over attic spaces only (recommendation has been to NOT have anything in front of radiant barrier).
5. Reinstall R-22 batted fiberglass insulation currently in cathedral ceilings before adding as many Polyiso rigid foam boards on top of R-22 to where boards touch the new sheathing.
6. Install normal plywood sheathing cathedral ceilings and non-attic (was advised that I couldn’t use radiant barrier due to no airspace).

I’m good with the rest of roof – underlayment and the tiles.  I guess the only thing worth mentioning is that I’ll be doing composite shingles where the solar panels are instead of mounting on the concrete tiles directly.

Unfortunately, I don’t think I can add Polyiso on top of the sheathing because of how I’m venting the attics with o’Hagins.  Also I’m not sure I would like my  fascia any higher than it currently is – currently it’s a 2×10.  

Sorry for the long post.  Hope this makes sense to you all.  Thank you in advance for reading.

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Replies

  1. Jon R | | #1

    Not completely clear to me, but why not skip all venting and have only an un-vented, foam above the sheathing design?

  2. E A | | #2

    @Jon R - I only recently learned about rigid foam above the sheathing from this forum. I suppose I could look into an unvented attic too. Does the above not work?

  3. E A | | #3

    Forgot to mention I also have a whole house fan in Attic 1 so I need the ventilation.

  4. GBA Editor
    Brian Pontolilo | | #4

    Hi EA,

    Welcome to GBA. Most of what you are intending to do makes sense to me. I am unclear however, in #5, where you intend to put the rigid foam. Can you clarify?

    Also, here's a reading list that will be super helpful with your project:

    https://www.greenbuildingadvisor.com/article/all-about-attics
    https://www.greenbuildingadvisor.com/article/all-about-attic-venting
    https://www.greenbuildingadvisor.com/article/radiant-barriers-a-solution-in-search-of-a-problem
    https://www.greenbuildingadvisor.com/article/how-to-build-an-insulated-cathedral-ceiling

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