Double check my insulation plan!
I’ve just finished air sealing the attic of my home and am now creating a plan to install more insulation. Would like to get some feedback before moving forward.
The house is in zone 4c (Portland) and the roof is fully hipped, 4/12 with the “not enough space at the eaves” dilemma common in older homes. It’s vented (12 vents spread around perimeter) and some existing older fiberglass loose fill (the semi-chunky white stuff).
Here’s the plan so far:
1. Test air sealing w/ blower door test. Fix problem areas before proceeding.
2. Replace vent baffles and block around baffles w/ rigid foam.
Also block around rafter bays adjacent to vents to prevent wind washing or accidentally filling soffit vents (1-2 bays to each side of vent).
3. Re-spread existing fiberglass. It was universally a few inches above the joists before air sealing, but all my digging and rolling around to air seal has created lots of mounds and compressed areas.
4. Wrap chimney in rockwool to maintain separation from new blown-in.
5. Blow new cellulose to (at least) R-49. Attempt to fill all the way to the outside of the exterior top plates without filling the soffit.
Where I could use clarification:
1. Do I need to baffle all the way around the entire perimeter to keep the new blown in out of the soffit? Or just around the vents? The old blown fiberglass extended all the way out without any baffling. Not sure how they achieved that. Wind-washing issues seem irrelevant except near the vents.
2. Any harm in insulation contacting roof sheathing? Thinking I need to pack the eave areas as much as possible to best counteract the lack of space.
3. Should I spread the existing fiberglass evenly before adding new cellulose? Right now, I have it raked back from the eaves so that I could air seal the exterior top plates. Thinking I should leave it that way so there’s more space for cellulose. And, throughout the attic, my digging and rolling around has created both areas of compressed fiberglass and giant, fluffy mounds of it.
4. Any use in insulating over the (unconditioned) attached garage?
5. Planning to insulate to r-49 but maybe r-60 is worth the additional time and materials? Not sure how to find the sweet spot.
Thanks so much.
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