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Typical Air Infiltration Rates?

 
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Old 02-20-2019, 06:27 AM   #21
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Re: Typical Air Infiltration Rates?


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Originally Posted by Golden view View Post
Years of well-funded testing and data logging (by the CCHRC) in much worse than real world conditions, the simple science of dew point calculations for an insulation assembly, and my own investigation have proven this is a valid assembly for the climate in which it was installed: The sub-arctic of Fairbanks, Alaska with about 14,000 heating degree days per year.

Warmer climates could have a larger percentage of insulation inside the vapor barrier (Again, see dew point calcs). Cooling climates require different considerations.
Sorry I spaced you were talking about the North Pole climate for that assembly which definitely has its own special challenges & of course building it tight sure helps. As for most of the US though - I stand by what is said
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Old 02-20-2019, 08:59 AM   #22
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Re: Typical Air Infiltration Rates?


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Originally Posted by SLSTech View Post
Sorry I spaced you were talking about the North Pole climate for that assembly which definitely has its own special challenges & of course building it tight sure helps. As for most of the US though - I stand by what is said
I would be curious to see how such an assembly would fail in, say your area. I presume you're concerned about cooling season.

And unrelated, seriously not trying to be a D, but you will increase your sales generated from your website if you stop using that apostrophe incorrectly.
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Old 02-20-2019, 10:37 PM   #23
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Re: Typical Air Infiltration Rates?


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Sorry but I hate to say this, but I would describe it more as a train wreck... Yes you can place a barrier in the middle which means that you have to (ok should) allow for it to dry to both the inside & outside. The catch is, think about how heat flows - only half the assembly will be able to dry at a time while the other half will stay stagnant / build up more. Besides that, you now have a solid surface for condensation to build up



You basically have 2 air/vapor barriers in all houses - down south they mainly only fret over the exterior while up north most only fret about the interior - a smart person deals with both as any air/moisture movement moving through short-circuits the insulation (it doesn't matter how or where) You get your moisture, thermal, & air control layers right a lot of the BS drivel you read is meaningless



As for plastic sheathing - yeah that should only be in the coldest of climates or as Joe Lstiburek simply points out, only in a house that has no air conditioning (I would say needs)


I found this while researching this topic. Ole Lstibureck seems to like the idea.

To make sure were on the same page, this middle layer is only an air barrier and vapor retarder.


https://www.energyvanguard.com/blog/...ud-Wall-Design


https://www.buildingscience.com/docu...sure-assemblie


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Old 02-21-2019, 07:41 AM   #24
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Re: Typical Air Infiltration Rates?


"consider to risky..."
The middle layer can be an air barrier & retarder but you have to have to concentrate on the other two - you don't want that middle area to be your primary. one reason why he likes osb (really plywood as he hates OSB) in between the two walls is how hard it is to insulate that large space properly.

Back to the prior one - yes Golden's is golden in Alaska but not further south unless you might be in say International Falls MN, far north North Dakota, etc... As listed in BSC's summary "This is highly insulated wall system that will work in extreme climates as part of a high-R enclosure."
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Old 02-21-2019, 10:48 AM   #25
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Re: Typical Air Infiltration Rates?


The double stud wall and close cousin the larsen truss wall are a bit tricky because of their limited drying potential. The sheathing on the back side of the inner wall has to be meticulously air sealed for it to work, and is a less risky if using dens pack cellulose over fiber insulation. I've been follow a lot of the latest incarnations of this type of assembly and a lot of high performance builder have forgone with the outer sheathing in favour of wrbs that also act as cellulose netting (like this) to provide more exterior drying potential. In both cases sheathing or wrb, it's imperative to use a rainscreen to further aid in outward drying potential. The inherent risk in the assembly is that plywood or osb is essentially a class II vapour retarder so that section outboard between the layers in internal sheathing and external sheathing can have trouble if moisture gets in the wall and be susceptible to cold sheathing concerns. In Europe they'll often use a vapour permeable fiberboard insulation on the exterior for this reason.


I've only ever evaluated this type of wall for cold climates, so I can't speak to SLS's concerns about how it would perform in mixed or hot climates.

The reason why people tend to like this assembly is because they can use inexpensive and environmentally friendly cellulose to get really high r-values. The less risky approach would be to have a continuous layer of insulation on the exterior held with rain screen furring strips. The amount exterior would be dictated by your region for inboard/outboard ratios if using a low permanence outboard insulation like foam board, in order to keep the sheathing above the dew point. Outboard insulation however can get tricky to detail flashings for windows and doors if the wrb is behind the outboard insulation.
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Old 02-21-2019, 01:17 PM   #26
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Re: Typical Air Infiltration Rates?


I read in one of the articles I linked that ideally the exterior sheathing plan would be 5 times more permeable than the inside sheathing plan to promote outward drying.

I had a neighbor that built with double stud and no exterior sheathing 35 years ago. Great system except for the family of raccoons that moved into the wall due to an exploited opening and no sheathing !


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Old 02-21-2019, 07:11 PM   #27
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Re: Typical Air Infiltration Rates?


The director of the CCHRC was a builder and did some interesting experimental homes. One, if I remember right, had around R-60+ Larson truss walls and R-100+ ceiling. Might have even been R-90 and R-150. It was a round, single story house so there was more ceiling than wall area. The ceiling was sheathed in OSB just for the weight of the cellulose.

But the heating system was the neat thing: Solar collectors that fed a 5000 gallon water tank in the center of the house. That held almost enough thermal mass to get through the winter. Consider that in Fairbanks, the temp will be -50 and the sun barely shines for a couple hours and at such a low angle, that for a couple months those solar collectors probably never got above freezing. It started heating the house early in the spring, when there's quite a bit of sunlight but the snow on the ground keeps the air quite cool.
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Old 02-21-2019, 07:36 PM   #28
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Re: Typical Air Infiltration Rates?


Quote:
Originally Posted by Golden view View Post
The director of the CCHRC was a builder and did some interesting experimental homes. One, if I remember right, had around R-60+ Larson truss walls and R-100+ ceiling. Might have even been R-90 and R-150. It was a round, single story house so there was more ceiling than wall area. The ceiling was sheathed in OSB just for the weight of the cellulose.

But the heating system was the neat thing: Solar collectors that fed a 5000 gallon water tank in the center of the house. That held almost enough thermal mass to get through the winter. Consider that in Fairbanks, the temp will be -50 and the sun barely shines for a couple hours and at such a low angle, that for a couple months those solar collectors probably never got above freezing. It started heating the house early in the spring, when there's quite a bit of sunlight but the snow on the ground keeps the air quite cool.
I think you're talking about Thorston Chlupp's SunRise House. He did a couple really interesting presentations on it
. The CCHRC did a long term monitoring and analysis of the house, very interesting report found here

They built a number of similar houses after that.
another one to that the CCHRC did to demonstrate that regular builders could achieve the same results.

Very interesting stuff. Some really wild thermal storage system solutions going on there.
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Old 02-21-2019, 08:11 PM   #29
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Re: Typical Air Infiltration Rates?


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Originally Posted by duburban View Post

I had a neighbor that built with double stud and no exterior sheathing 35 years ago. Great system except for the family of raccoons that moved into the wall due to an exploited opening and no sheathing !

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I have a house that is 120 years old with no weather barrier, Solid timbers, 1" of stucco and wire mesh and raccoons moved into it too, so I don't really see your point. Both are maintenance issues.
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Old 02-21-2019, 08:24 PM   #30
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Re: Typical Air Infiltration Rates?


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Originally Posted by Philament View Post
I think you're talking about Thorston Chlupp's SunRise House. He did a couple really interesting presentations on it here. The CCHRC did a long term monitoring and analysis of the house, very interesting report found here

They built a number of similar houses after that. Here's another one to that the CCHRC did to demonstrate that regular builders could achieve the same results.

Very interesting stuff. Some really wild thermal storage system solutions going on there.
That's right. I had the guy wrong. Chlupp's an interesting guy. It's been a while since I moved away from there.
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Old 02-21-2019, 08:33 PM   #31
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Re: Typical Air Infiltration Rates?


Id like to understand more on how to size that thermal mass to sail over a winter. Id imagine youd anticipate your heating load and try to get as many btus charged up.

Havent clicked the links but Im curious how they pulled heat from it, passively or actively.


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Old 02-21-2019, 08:36 PM   #32
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Re: Typical Air Infiltration Rates?


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I have a house that is 120 years old with no weather barrier, Solid timbers, 1" of stucco and wire mesh and raccoons moved into it too, so I don't really see your point. Both are maintenance issues.


My point is that the exterior sheathing plane is a hard thing for me to let go of. It makes repairs easy and defines the outside of the home. A siding and strapping layer over membrane just doesnt feel right to me. But I will adjust!


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Old 02-21-2019, 08:40 PM   #33
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Re: Typical Air Infiltration Rates?


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That's right. I had the guy wrong. Chlupp's an interesting guy. It's been a while since I moved away from there.
I've never met him, but he seems like an intense fellow. You can just tell by his presentations that he's operating on a different frequency. I really admire his work, more so than the slew of building scientists. He's just an extremely knowledgeable builder that tries things then tests the crap out of it.
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Old 02-21-2019, 08:47 PM   #34
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Re: Typical Air Infiltration Rates?


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Originally Posted by duburban View Post
Id like to understand more on how to size that thermal mass to sail over a winter. Id imagine youd anticipate your heating load and try to get as many btus charged up.

Havent clicked the links but Im curious how they pulled heat from it, passively or actively.


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It's a 5000 gallon tank that is heated primarily through solar thermal. Because of the volume they leverage stratification in order to keep the top at around 160F. So even in the winter in Fairbanks Alaska, the bottom of the tank can still be heated. There is a pump that circulates it through the hydroic heating system. There is a secondary 40Gal domestic hot water tank that is suspended in the 5000gal tank, which can be supplimented by a heating coil in the masory heater if needed. It's wildly complex, yet kind of simple. He explains it really well in the video.
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Old 02-21-2019, 10:33 PM   #35
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Re: Typical Air Infiltration Rates?


Quote:
Originally Posted by duburban View Post
Id like to understand more on how to size that thermal mass to sail over a winter. Id imagine youd anticipate your heating load and try to get as many btus charged up.

Havent clicked the links but Im curious how they pulled heat from it, passively or actively.


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Calculating thermal mass of water is pretty easy, because it's what BTU's are based on.

1 BTU heats one pound of water 1 degree.

5000 gal x 8.34 lb per gallon = 41,700 BTUs released for every degree the tank drops. Which, if you think about it, isn't really that much. Rounding now: You could maybe get 4 million BTU's (40 therms, or around $40 of natural gas) of usable storage, which is a few days of heating a 2000 sf inefficient 1970s house in that environment.
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Old 02-24-2019, 09:33 PM   #36
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Re: Typical Air Infiltration Rates?


Id have to say that in the northeast with all the poly vapor barrier that was installed in the 8s and 90s that 4 ach is about as good as youd see.
I just helped my old man build his to die in house. We did a mix of wall assemblies. Double walls, foam on exterior, foam on the roof. All with a rain screen and smart vapor retarder on the walls without foam. Came in pretty tight. .5 ach. Im still looking for the sweet spot in details for the most bang for the buck from a building point
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Old 02-24-2019, 10:43 PM   #37
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Re: Typical Air Infiltration Rates?


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Originally Posted by Golden view View Post
Calculating thermal mass of water is pretty easy, because it's what BTU's are based on.



1 BTU heats one pound of water 1 degree.



5000 gal x 8.34 lb per gallon = 41,700 BTUs released for every degree the tank drops. Which, if you think about it, isn't really that much. Rounding now: You could maybe get 4 million BTU's (40 therms, or around $40 of natural gas) of usable storage, which is a few days of heating a 2000 sf inefficient 1970s house in that environment.


I ran my model with ideal r values and ended at about 3 cord of wood which is about 3 times 14,000,000 btu. So yeah, you would have to be putting heat into that storage tank every minute of every sunny day.

There is a thermal mass component in my energy modeling which I will play with. Ill try to add that 5000 gal tank and see what happens. Id imagine it helps the building thermal sail overnight.


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Old 02-24-2019, 10:45 PM   #38
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Re: Typical Air Infiltration Rates?


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Id have to say that in the northeast with all the poly vapor barrier that was installed in the 8s and 90s that 4 ach is about as good as youd see.
I just helped my old man build his to die in house. We did a mix of wall assemblies. Double walls, foam on exterior, foam on the roof. All with a rain screen and smart vapor retarder on the walls without foam. Came in pretty tight. .5 ach. Im still looking for the sweet spot in details for the most bang for the buck from a building point


Nice job. How did you air seal your double stud walls?

Until recently the double stud was a no-brainer but Im seeing efficiency in a 2x6 wall with exolation. Add air barriers mid wall assembly is a major effort.


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Old 02-24-2019, 11:03 PM   #39
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Re: Typical Air Infiltration Rates?


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I ran my model with ideal r values
What does "ideal r-values" mean?
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Old 02-26-2019, 08:31 PM   #40
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What does "ideal r-values" mean?


Its my version of ideal: 12 sub slab, 40 walls and 60 roof. Similar to pretty good house theory that went around a while ago as counterpoint to the passive house movement.

And 3ach50 infiltration

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