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Cape vs two-story with 4:12: air seal/insulate/savings?

mikeysp | Posted in General Questions on

My buddy in zone 4a is thinking Cape Cod so he can have a couple rooms upstairs. He has asked my counsel as I am a second grader in building science and he is still in kindergarten. I have done some searches and I think I am going to advise him to go for a full 2-story with shallower pitch. Is this wise?

Am I correct to say:
1. Air sealing/insulating wall to roof will be more difficult (short of a “perfect wall” design).
2. Dormers make life much more difficult to keep out water (metal roof) as well as more difficult to get good airflow.
3. The cost difference is not that much more since a cape roof will need to be much thicker for insulation purposes. House will be about 24-28ft wide
4. shallower pitch supported near mid point by hall wall will require much less beefier trusses, be very easy to get the air/insulation details right, and make for a much easier roof install and future maintenance schedule.

Thank you for your sanity check all building science high schoolers and college grads 🙂 so I do not spew out nonsense. 

Thank you GBA community for sharing your wisdom.


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  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Mike.

    I can't comment on construction costs when it comes to the structure, which depend on too many factors. The details of a two-story home will make air sealing and insulating well a more cost-effective and less problematic approach. Simply put, an air sealed insulated ceiling and unconditioned vented attic are straightforward to design and build, and they work.

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