GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Attic R20/R28 upgrade to R50 near Seattle with no AC – worth it?

canada_deck | Posted in General Questions on

Half of our attic (in a converted garage) is currently R20 fiberglass batts.  The other half (upper floor of a two story house) is R28 fiberglass batts.  We live in a climate that is basically the same as Seattle.  We do not have AC in the house.  Heat is electric resistive.

We’re looking at upgrading the insulation in the attic.  It will be a bit of an undertaking since there are no baffles installed currently (enough air gets past the batts to avoid a mold problem).  The plan is to install baffles and then blow in loose fill fiberglass insulation to bring each area up to R50.

The house itself is not very energy efficient.  The converted garage has 2*4 walls.  All of the windows are from the 80’s and there are some huge windows.  In the long run, we will be installing a heat pump and replacing all the windows but that won’t happen for a few more years at least.

Do you think we will notice an improvement in comfort and reduced energy bills from doing this attic upgrade?

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. walta100 | | #1

    I see insulation as frosting on a cake before you put on the frosting you must make the cake and before you insulate you need to air seal your house. Insulation is useless if the conditioned air in your house is allowed to leak out.

    You may find this article interesting.


  2. Andrew_C | | #2

    After you follow Walter's suggestion to air-seal first, I'd recommend blown cellulose instead of fiberglass on top of your existing fiberglass batts. A cellulose cap will reduce air flow thru the insulation, and give you better noise reduction. When I've done this in the past on my own houses, it definitely improved things, including making the house quieter. But again, air-sealing should happen first.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |