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Old 04-27-11, 06:32 AM   #21
RobertSmalls
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Originally Posted by S-F View Post
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.
There are some good points here, but also a few things that are not universal.

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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Old 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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Old 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.

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Originally Posted by S-F View Post
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
Wow, S-F... you have your own blower door?

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.

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Old 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.
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Old 04-27-11, 12:49 PM   #25
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Originally Posted by AC_Hacker View Post
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.

-AC_Hacker
An interesting point: I was recently talking to some German passivehaus folks and they were saying that foam is better because there is a potential for the cellulose to have a negative impact on the indoor air quality with airborne particulate matter in a negative pressure situation. Negative pressure is a little more feasible in a house with electric range and direct vent DHW and heat. Seems nuts to me as the foam at best can't be doing anything to help the air quality (which cellulose can by way of moisture mitigation) and very probably is off gassing some things I don't want to breathe. I'd rather wrap news papers around my head than spray foam all over it.
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Old 04-27-11, 10:47 PM   #26
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Default 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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Old 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?)
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Old 04-28-11, 11:45 AM   #28
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...the Moscow data point...
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.

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Old 04-28-11, 12:51 PM   #29
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Default Passive House "Best Practices"

Some Passive House Power Point slides... a bit of overlap but good ideas..

Link 1

Link 2

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Old 04-28-11, 04:04 PM   #30
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I see that the biggest lack in energy efficient knowledge is in the field of tightening up old houses.
S-F,

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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