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Old 12-07-12, 03:42 PM   #2
Apprentice EcoRenovator
Join Date: Aug 2012
Location: California
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Hi AC,
I glanced at the article to get summary points because I could easily see that I'll need to put a lot of energy into reading it to get all the implications. I'll do that later because I enjoy physics anyway.

One thing I immediately got out of it though was that insulating walls came to only 10% of the improvement of fully insulating a house. The other thing that jumped out at me was that insulating floors contributes 38% of the improvement. And I've noted elsewhere that insulating floors can create problems of their own when moisture laden air enters a crawl space in warm weather, condenses in the cooler crawl space and then causes mold and wood rot problems down there. The real problem is that by insulating between floor joists, which most people do, you keep the conditioned air out of the crawlspace and make the condensation problem worse! And because the joist themselves are not warm, even though the floor now is, you invite a perfect storm of wood rot through the floor joists that will eventually lead to moisture driving through to the floor itself. So if you have wood floors and you decide to insulate beneath the floor you will warm up the floor. But you will also cool off any crawlspace you might have. That's really bad and will likely cause problems eventually, even including cupping of the floors.

I've learned all this just a bit late because a few years ago I did exactly the wrong thing and put insulation between the floor joists. I since taken most of it back out. Luckily I haven't yet put in new wood flooring that I eventually plan on putting in. Next project (after current construction on other things) is to seal, insulate, and put in conditioned air into the crawlspace and treat it like living space (except for not living down there). An added benefit is that if I ever go ahead with my ten year plan of putting in solar hot air panels that hot air will go right into the crawlspace and act as a heat reservoir while simultaneously making the floor warm.

The main thing I'm hoping to convey from this message is that one shouldn't automatically read your article and start insulating the floor. Depending on the circumstances it could create other problems along with warming your house. Overall the article you reference is really good and useful and i'm already learning from it. I just don't want people to jump to destructive conclusions on their own. That already happens too much, as we both know.

Last edited by Exeric; 12-07-12 at 04:05 PM..
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