04-27-11, 06:32 AM | #21 | |
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Foam is rated based on its "stabilized R-Value". The R-value drops over the first two years or so, but then plateaus after all the bubbles that are going to collapse have done so. The R-value would be higher than advertized during the first two years. Of course, fiberglass and cellulose settle and lose R-value over time too, so it's smart to compare aged to aged. Unlike fibrous insulations, the R-value of foam is not affected by wind. It forms a very durable barrier to air and vapor. The fact that it repels water while cellulose absorbs it seems more like a bonus than a drawback. They do burn energetically, but they contain fire retardants, and meet fire code when installed behind drywall. Good enough for me. And yes, in the event of a structure fire, I'll pop on a charcoal respirator. Different blowing agents are available. The used to use CFC's. R134a is one option, which is ironic considering its GWP. Other foams use various inerts, including CO2. To tell a contractor to spray foam, without specifying a specific foam and friendly blowing agent, would be crazy. However, whether adequate performance can be derived from, say, a CO2-blown foam remains to be seen. The Rth of air at STP is about R-5.5 per inch, so that's the best you can do with tiny bubbles of immobile air. |
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04-27-11, 07:44 AM | #22 |
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Dense pack will never loose R value as it's beyond settled density. Loose fill will though. There are two measurements for it's R. One is new and one is settled. These foams are showing to loose considerable R value over time. Much lower than their spec. The gasses continue to escape into the air. It just takes some time. Maybe 20 or more years. But most people building these days only think about the next decade at most. The hygroscopic value of cellulose is very good. It moisture levels. It doesn't absorb it and hold it unless it's soaking wet. It will facilitate drying of all of the structure. The foam rejects moisture forcing it into the lumber. This is a great plan for rot. In such a house humidity will need to be carefully controlled and kept to a minimum.
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04-27-11, 12:06 PM | #23 | |
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Rearding foam vs cellulose, I started my house insulation with foam because at the time the other choice was fiberglass and I wanted much higher R-value per inch. Even though foam was more expensive, it seemed like a good choice. Now that I have done most of my house, and the results are encouraging, were I to do it again, I would go with cellulose... maybe with a foam skin against the outside wall to stop the leaks, then dense pack in the remaining space (I increased the space to 6 inches).
I really like what I have read from eco-savvy Europeans... they seem to have a more thoroughly-internalized understanding of embodied energy, and carbon sequestration. Here in USA, 50% don't believe in evolution (for them personally, it apparently didn't happen) and about the same number doubt that global warming is occurring, or that it is a concern. That's pretty dismal... something crucial has failed in our society. So, I think it is easier for Europeans to encompass the many aspects of eco-decisions, such as what to use for insulation, and to see that R-value alone is not enough to make a decision... there is also embodied energy and sequestration of carbon. I really think that when all the factors are weighed, better choices can be made. Quote:
You've been holding out on us. Got any pix of it? BTW, regarding camera, I don't know if you are a thrift store junkie like I am, but very good 4 and 5 Meg still cams are pouring in to the Goodwills all across our fair country. Be sure to take some good batteries with you and test them out before you buy. I picked up several and gave them to friends who hadn't gone digital yet. I was paying $40, now they are typically $10 to $15. -AC_Hacker
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04-27-11, 12:29 PM | #24 |
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I rent a blower door when ever I need one. I admit it would be pretty cool to have one but I can't justify the $2,700 cost. I rent them just up the road a mile. The place is right across the street from where I'm moving. That's also where I get spray foam and other materials. But I'll definitely document the leak testing thoroughly when I do it.
Thanks for the tip on the thrift store cameras. I never would have thought of that. Unfortunately (fortunately?) where I live there is an abundance of thrifty people so the goodwill is usually bone dry. I'll have to go up the river to one of the other towns or troll some thrift stores next time I'm in Boston. |
04-27-11, 12:49 PM | #25 | |
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04-27-11, 10:47 PM | #26 |
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EcoRenovator's heating degree days...
Here are some heating degree days for some of the many past and present EcoRenovator posters.
I used this URL to get 5-year average degree day info. I tried to get a variety of locations, and in most cases I needed both a city and state (or country). In a few cases, I just guessed. higgy Winnipeg, Manitoba 10422 Maxis Riga, Latvia_ 7800 Daox Germantown, WI 7138 Piwoslaw Warsaw, Poland 6722 Xringer Woburn, MA 6412 Big Al Glasgow, Scotland 6319 osolemio Copenhagen, Denmark 6230 TimJFowler Santa Fe, NM 5755 AC_Hacker Portland, Oregon 4576 Hugh Jim Bissel Dallas, Texas 2244 ?????????????????????????????????????????????????? ????? if you are not included on the list, not to worry, I was trying for a variety of locations. You can go to the degree-day URL, find your average degree day, and cross check on the chart to find your own wall thickness. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Then I took a look at this table which showed Passive House wall thicknesses for various locations in Europe. I then found the heating degree days for each location mentioned on the chart, and did a point scatter of degree days vs wall thickness and did multiple curve fits on this data scatter and found that a linear fit was not perfect but still close enough to be very interesting. So I used the formula from that linear fit, converted all cm wall thicknesses to inch wall thicknesses, and Applied it to the EcoRenovator list to see what Passive House wall thickness would be about right for their location's heating degree day figure. So this chart should give you a rough idea of how thick your Passive House wall thickness might need to be. This assumes that a HRV of certified 80% or better efficiency was used, and that Passive house standards of insulating and sealing, etc were adhered to. Kind of interesting don't you think? (NOTE: data error has been repaired) -AC_Hacker
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I'm not an HVAC technician. In fact, I'm barely even a hacker... Last edited by AC_Hacker; 04-28-11 at 09:58 PM.. |
04-28-11, 06:32 AM | #27 |
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I'm surprised how good that linear fit is, considering all the factors that could skew it. HDD indicates how long * severe a winter is, but insulation thickness in a passivhaus with adequate thermal mass really only depends on the coldest week, and sunlight levels.
I see you have R=0.90. Can you get that higher by correcting the Moscow data point? (I assume that Moscow is colder than Brittany, else why would Napolean have run into trouble?) |
04-28-11, 11:45 AM | #28 |
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There are many factors that could explain outlying data points. Passive house design takes many factors into account.
I did this work to suggest what wall thickness might be needed for various location's HDD, hoping that it could initiate further interest in Passive House design. If this is useful to you, use it. If it is not useful to you, please disregard it. -AC_Hacker
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04-28-11, 12:51 PM | #29 |
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Passive House "Best Practices"
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04-28-11, 04:04 PM | #30 | |
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Quote:
Since you're contemplating a major insulation overhaul (Deep Energy Retrofit), I came across some really good sites that address just such a thing: Deep Energy Reduction Retrofit with Passive House Tools Remodel Project: Deep Energy Retrofit Deep Energy Retrofit of a Sears Roebuck House This is a Swiss outfit that specializes in air-tight layer construction. There are also some Youtube videos that could be helpful. -AC_Hacker
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