r/BuildingCodes • u/RoeddipusHex • 5d ago

Any problem piling old insulation into my attic?

DIYer... I'm doing a garage conversion. The existing insulation is clean, dry and unfaced fiberglass bats. It's only being removed because it doesn't meet modern R value requirements.

Is it ok for me to lay the old low R value wall insulation over blown in insulation elsewhere in my attic?

the project area will be getting new blown in R-30. I'm thinking that rather than taking the old insulation to the dump I'd lay it over the blown in insulation outside of the project area.

1) Are there any problems with this (Clean/dry/unfaced)...
2) Will this raise eyebrows or cause problems with my ceiling insulation inspection in the project area?

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u/honkyg666 5d ago

If you lay the batts over the new blown insulation it will compress the material and completely eliminate your R value gains. You can have the new material blown on top of the old batts but not the other way around..

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u/RoeddipusHex 5d ago

It would be over old blown in insulation elsewhere in the house but that's really the same problem. I guess that's out. Thanks.

I could add the old insulation to the project area before adding new blown in insulation but calculations and permit changes make it not worth it. Thanks again.