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Community and Q&A

Raised-Heel Roof Trusses and Insulation R-Value

JMrtns | Posted in Energy Efficiency and Durability on

Hi GBA Community, New build in Zone 5. I’m wrapping up the Roof Truss design and I’m having attic space built in. The designer is including a energy raised heel into my model although I don’t like the way it looks because its 16″ high. Is there any to decrease this heel and still hit R-49? Is there a combination solution I can use? (We’d like to avoid using any spray foam, the only one I would consider is that Natural Polymer solution I’ve seen out there lately)

Bonus: The plan is to finish this space in the future. I was reading that its best to insulate the roof line from the soffit to the eave so that the entire space is in the conditioned space. (in Red) I spoke to an insulation contractor and they said this wasn’t the recommended approach with a roof truss because of lack of access. They recommended the approach I highlighted in blue. Is there any downside to this approach? By the way, why would the roof line approach be recommended when the trusses are built with only 2×4’s and 2×6’s? How can you meet the R-49 value which such a small cavity? Am I missing something here?

Edit: Added some example captures from the design. Is there anything that looks off here?

Thanks, Jason

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Replies

  1. Expert Member
    Malcolm Taylor | | #1

    JMrtns,

    Attic trusses have two Achilles heels: The lack of depth, especially where the wall meets the ceiling, and the difficulty of air-sealing. Martin explains this and the possible solutions much better than I could in this article: https://www.greenbuildingadvisor.com/article/bonus-room-problems

    1. JMrtns | | #2

      Malcolm, is there anything I need to be aware of when it comes to thermal bridging where the knee wall meets the roof line (the corners)?

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