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New detached garage! – Questions on insulation plan

Joe Watson | Posted in General Questions on

Hi Everyone,

Finally built my detached garage (48×30)and working on the insulation plan.  It will be drywalled and HVAC at some point.  The trusses are on 19.2″ centers.  The room trusses (32ft long) have a 2′ raised heel to give me a 10ft. ceiling on that side of the garage, while maintaining a 12ft wall for the scissor truss bay for a 10k car lift.  The walls are 2×6.   There is a pull down stairs to access the attic space from inside and there will be an outside staircase built for a gable end door eventually.
My initial thought is to us 1×2’s and attach them to the sides of the truss right under the deck and then use OSB, polyisio or something else to give me a air 1.5″ air channel from soffit to ridge vent.  I would use caulking (polyurenthane?) to seal all the edges.  Then use rock wool or pink to fill the cavities.  I am in Richmond, VA (Zone 4).
For HVAC, I was thinking 2 mini-splits downstairs, but then the attic room would be unaccounted for.  Wondering if a regular heat pump with traditional ductwork would be better?
Any thoughts or advice?


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  1. Expert Member
    Michael Maines | | #1

    Joe, this article covers the relevant details for insulating a cathedral ceiling, which is what you have: If you don't have a membership, it's worth the price. Or just do a trial membership first. Briefly, your approach should work.

    I'll leave the heating question to others who have more experience heating this type of space.

  2. Joe Watson | | #2

    Thanks Michael,

    Appreciate the link and the feedback. I am also exploring if there are any DIY air sealing sprays I can use for the wall bays. I just used two tubes of Sika Pro Select construction sealant between the sill plate and the block on the outside. I did it with a manual caulk gun and the thought of doing every bay is daunting! ( i would get a air powered caulk gun)

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