Near Passive House Retrofit...
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I hope you start a well-documented thread, I think there will be great interest in your efforts. Best Luck, -AC_Hacker |
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I hope you start a new thread on your project, I think there would be great interest in this. Best Regards, -AC_Hacker |
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Vacuum insulated triple glazing and 18" walls would be nice, but I view them as very expensive toys. I'm inclined to go with a very efficient, 2x6-framed, well sealed house with ventilation heat recovery and good, south-facing double-pane windows. Who knows; it might be passive nine months out of the year, and pretty close in August, January, and February. |
As the price of heating and cooling get higher in the coming years, I'm trying to
imagine what people will do to retrofit their 2x4 walls and lossy windows.. Adding two or four inches to the thickness of their walls and installing another window on the inside, sitting in a frame built into their new layer of interior wall.. |
The big problem with the spray foam (aside from the stupid cost) is that as the gasses escape over time the R value will decrease. Basically the best you can get from air is R 4. So these R 7 foams will slowly make their way down to to R 4 over the course of 15 - 20 years. They are also pretty nasty, high embodied energy, they give off terribly toxic fumes when burned and they drive moisture into the framing lumber. Cellulose draws moisture away from the lumber. It's also made form recycled news papers. There is no end to the benefits of cellulose. The only thing that foam has on it is R value. Just make you wall a little thicker. It'll be greener in every sense of the word. The indoor air quality will be much better. It will cost less. You can't go wrong.
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Stick built with cellulose insulation is going to be the best value. Add a nonloadbearing inner wall framed in 2x3's. Take time to caulk all the cracks, it makes a big difference.
Cellulose will settle over time, leave access panels at the top of the ceiling to add cellulose insulation every year until it stops settling. |
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How do you dense pack, tamp it down with a 2x4? What if you don't have access from above, how do you get the top part packed down?
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Just google dense pack cellulose. I have also seen some good videos on youtube.You can actually insert the tube into the middle of a cavity and dense pack the top down. When it's dense packed it will actually hold in place while you pack beneath it. The only way settling will occur is if it's done improperly. This doesn't happen in new construction because the wall get's packed before the sheet rock goes up so you can actually test all of the little nooks and crannies. There is no tamping involved. It's a combination of the pressure from the blower, adjusting the cellulose/air flow, using a smaller tube and technique.
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You can have a 24" spray foam wall that will do you nothing if your house moves that much air. In new construction (what we hear about most) making things air tight is pretty easy. Still getting to passivehaus levels (.6 ACH @ 50) is very difficult. Even getting to 1 is pretty hard. You need to put the blower door in backwards, pressurize the house and walk around with a smoke pen to find all of the air leaks. For an older house you could just pressurize and set up a fog machine to see where air is moving with some people on the outside also. |
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