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I've been touting the benefits of Spray Foam Insulation for years. It is actually incredible how much money you can save on HVAC every year. Your Heating and Cooling equipment can be halved in size and your living space is draft free and incredibly comfortable. Mate this with geothermal and your utility bills to heat and cool are equivalent to someones Starbucks habit (maybe less). If the North American building code was upgraded to a decent performance level (spray foam, triple pane windows, etc), we could probably get away with not having to build another power plant for decades.

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Spray foam is very expensive and is not sustainable. Mineral wool/rockwool is also fairly popular but pricey as well.

Also, it's not just adding insulation. Air tightness is hard problem to address for existing houses.

Spray foam pays for itself, so it's basically free in the long run. Interesting enough people don't bat an eye when someone quotes them 20-30 k for a new Kitchen but if you quote someone 20-30 k to insulate their entire house they look at you like you killed their mother and sister.

The average home has 2000 ft of linear cracks. Everything from poorly sealed doors, windows, and envelope. It's like the equivalent of keeping your front and back door open all year around. So even after spray foaming there is some leakage (blown door test).

Really, Spray foam isn't that expensive, you should be paying about $3 -$4 a sq/ft at around a R-21 which is cheaper than most tile or carpet installations.

https://huntsmanbuildingsolutions.com/en-US/

If I were building a house I would probably go with ICF forms all the way up and Spray Foam the attic and basement floor (under the concrete floor). If I were renovating, I would Spray Foam and try to make the job large enough to cover the contractors minimum charge. Even a couple of rooms can really help the utility bills.

Double stud construction with blown in cellulose is much cheaper than spray foam, and way better for the environment.

Also, if you want close to passive house, you'll need way more than R-21. I would say only use spray foam if your wall cavity is limited and you need the maximum R value.

Double stud construction cheaper? Maybe a while back...

Spray Foam although rated at R-21 preforms much higher since it seals. Blown in Cellulose settles, attracts dust, rodent nesting, and doesn't seal and isn't a vapor barrier or water proof. You get what you pay for I guess.

We have a house in Northern Ontario that is around 4000 Sq/Ft (entirely spray foamed). The costs to heat and cool it are 1/3 compared to the house 2800 sq/ft house in Toronto (insulated with Fiber Glass, Attic Cellulose).

The biggest hurdle is folks just don't give a fuck about the mechanical part of the house. Dry wall covers it all up. What's important is the finish that you see everyday.

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