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Community and Q&A

Over-Insulating Walls

ARodB | Posted in Energy Efficiency and Durability on

My 1960’s Cape Cod style house has fiberglass insulation in exterior walls. I’m improving air sealing in the attic and adding insulation, and I’m trying to decide if it’s worth having a contractor dense-pack the gable walls with either cellulose or fiberglass. Again, the walls do have fiberglass batts in them. How much of an improvement could I expect from dense-packing over existing (very old) batts?

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  1. Expert Member
    Carl Seville | | #1

    Adding more insulation in the walls could create problems by limiting the drying potential. It is likely that you don't have much if any of a weather barrier or flashing around the windows. The fact that the house is leaky and not well insulated has allowed the water that gets in to dry out without causing damage. Packing the walls with insulation will increase the risk of deterioration. I would focus in air sealing, sealing the ceiling or roofline and crawlspace or basement, improving HVAC, and adding storm windows. The improvement from insulating the walls won't be worth the risk

    1. ARodB | | #2

      Thank you. I will forget about wall insulation and focus on the knee wall space.

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