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Old 04-26-11, 03:35 PM   #11
AC_Hacker
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Default Near Passive House Retrofit...

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... I think that you could get lower than 20% with a retrofit. I'm buying a house so we'll see, won't we?
Certainly a very worthy goal.

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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Old 04-26-11, 03:40 PM   #12
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Quote:
Originally Posted by S-F View Post
...I think that you could get lower than 20% with a retrofit. I'm buying a house so we'll see, won't we?
A very worthy goal.

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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Old 04-26-11, 05:10 PM   #13
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Originally Posted by S-F View Post
In order to get to passivhaus levels you will need 16" - 18" walls (assuming you use cellulose) with no thermal bridging at all. I doubt you will find exactly what you want already set up for you but it wouldn't be too hard to adapt something to meet passive standards.
With some spray foam insulations claiming twice the stabilized R-value of cellulose, it might be doable with 8-9" walls with no thermal bridging, e.g. with steel studs. I wonder, would the increased cost of spray foam insulation be made up for by the savings in lumber, framing labor, window and door trim, and per-square-foot taxes?

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.
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Old 04-26-11, 06:01 PM   #14
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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..
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Old 04-26-11, 06:55 PM   #15
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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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Old 04-26-11, 08:33 PM   #16
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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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Old 04-26-11, 08:38 PM   #17
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Cellulose will settle over time, leave access panels at the top of the ceiling to add cellulose insulation every year until it stops settling.
If you dense pack it properly this will never happen. The 3.5 lbs./ft. of proper dense packing is so far beyond settled density that settling is not even remotely possible. If you leave access to the cavity you will invariable also leave air leaks that will cost you a ton in convective heat loss.
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Old 04-27-11, 05:35 AM   #18
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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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Old 04-27-11, 05:55 AM   #19
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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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Old 04-27-11, 06:13 AM   #20
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Quote:
Originally Posted by AC_Hacker View Post
Certainly a very worthy goal.

I hope you start a well-documented thread, I think there will be great interest in your efforts.

Best Luck,

-AC_Hacker
Yes I plan to document it thoroughly. I need a camera though. When the Mrs. moved out she took the camera along with everything else. I see that the biggest lack in energy efficient knowledge is in the field of tightening up old houses. On Saturday I went to a house that has already had 3 energy audits. I guess the work they did made a little difference. Not much though. I still managed to measure air pouring out of a recessed light at 2 meters/second. I couldn't even get the house to 50 pascals with the blower door. The home owner was all gung ho about installing insulation but it will do him little good when there is a hole in his basement going right into his unconditioned crawl space. o.0
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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