$400 vs. $4,000 for Insulation, what do I do?

My house is a duplex that had two entrances and when I converted one of the doors into a window, I was able to see  each element of my exterior walls.

The materials making my exterior envelop were: Bricks, Reflectix Duct Wrap and over 100 years old Wood. As I started asking question to a few different contractors and staff from hardware stores, everyone pointed in the direction of Fiber Insulation:  it’s the pink insulation that you’ve probably seen in home renovation shows &/or in your home.

Being a renovation enthusiast, my instinct told me that this one was too easy. I called my structural engineer  to probe and validate the information I had received. He had recommended that I use spray insulation for the crawlspace, and I wanted his input on the insulation for the rest of the house. That’s when he guided me to breakdown the R-Value within my exterior walls and adjust the interior wall accordingly.

In my geographic location, I needed an R-Value of 20  and here is breakdown of my exterior wall:

  • Brick R-Value is \approx \!\,0.2
  • Solid wood R-Value  \approx \!\,0.71
    • since my house was over 100, we can count it as zero…and can be considered as pourest
  • Reflectix Duct R-Value \approx \!\,6
  • Fiberglass of 3.5thick (the thickness of the interior wall) R-value \approx \!\,12

At best, I would have been at R-18 which did not meet the code requirement, therefore I had two options:

  1. Increase the thickness of the exterior walls in order to add thicker Fiberglass insulation
    • Pros: cost efficient, yet meet R-Value
    • Cons: exterior wall wouldn’t be air tight, wood is pourest, moisture will penetrate, lose an extra 3” on both side of the house
    • Approx Insulation cost: $400
  2. Urethane Insulation (spray foam), each 1” of spray foam has an R-Value \approx \!\,7
    • Pros: spray 3” for an R-value \approx \!\, 21,  spray is none-pourest total barrier from exterior weather, no need to thicken the exterior wall
    • Cons: very pricey
    • Approx Insulation cost: $4oo0

What did I go for?

I went for the most expensive route; being comfortable in your home is very important. Spraying insulation provides total barrier and is very energy efficient on heating cost. In design, every inches of space you can have counts and losing 6 inches was not an option 😉

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