We are wondering if it is safe for us to follow the energy experts' recommendation of blown in cellulose insulation in our attic.

Asked by Kris K
Woburn, MA

We were recently been advised by energy experts that blown in insulation in the attic is needed for energy efficiency. We also came to know, recently, that our house is done with aluminium wiring (in fact, entire neighborhood seem to be that way). So, we are wondering if it is safe for us to follow the energy experts recommendation on blown in cellulose insulation in the attic? The wiring seems to be in very good condition - fully insulated cables and there are no exposed connections or anything like that in the attic. Please advise if it is safe to go with blown in cellulose insulation?


Lucas Johnson

Answered by Lucas Johnson

Seattle, WA

Cascadia Consulting Group

April 3, 2012

Blown insulation is a great strategy for improving the comfort and efficiency of your home.

However, there are a few things to consider:

  1. You need to air seal your attic space first (using expanding spray foam, light covers, rigid foam board, etc.). You should target sealing can lights, bath fans, attic hatches, interior walls, pocket doors, etc.
  2. It may be worth investing in a full attic cleaning first so as to remove existing toxins, allow for better air sealing (due to access), and to allow the blown insulation to settle more effectively.
  3. You NEED to have a qualified electrician and/or insulation contractor come review the existing wiring system to make sure it is safe!!! Blown insulation will need to be installed by a professional, so they should be able to tell you if it is safe.
  4. If air sealing your home, you should be sure to measure the air exchange rate with a "Blower Door Test" conducted by a certified Building Performance Institute ( technician.
  5. Typically it is worth testing the air leakage in the existing ductwork as well, and more times than not, it is worth upgrading ductwork as part of your attic upgrade. Average ductwork leaks over 28% of the air, which means wasting money and actively pulling toxins into your home.

A good system typically consists of:

  • R-8 flex duct,
  • air sealing all registers/plenums/etc, and
  • having a system leakage rate of 5% or less.

Please let me know if you have any additional questions. I know I just added a lot of potentially complex items to consider; however, it is important to me that people do this project correctly the first time.

I hope this helps!

Tagged In: attic insulation

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