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Typical Air Infiltration Rates?

 
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Old 02-17-2019, 01:45 AM   #1
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Typical Air Infiltration Rates?


Iím working on an energy model for a house in design.

Iíd like to show the client an energy model with average compared to target 1.5-3 ach/50.

Anyone know what kind of blower door tests a typical house with no air sealing gets? Something built from 70s up?

Found a study that looked at over 100 homes in the Pacific Northwest and California with the average being 7-12.






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Old 02-17-2019, 08:51 AM   #2
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Re: Typical Air Infiltration Rates?


Up in Vermont I would think you might be a little less especially if you have plastic sheathing up in the walls (maybe 5-7).
With that if you want accurate you have to Test. I have been in "identical" homes on the same block with a difference of 3 ach between them
So how are you modeling said house

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Old 02-17-2019, 09:17 AM   #3
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Re: Typical Air Infiltration Rates?


I'd sure be curious to see what a blower door test would show on homes here in the PNW. The new homes I built in Alaska tested to around 1 ACH50. And I didn't tape the house wrap.
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Old 02-17-2019, 10:34 AM   #4
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Re: Typical Air Infiltration Rates?


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Originally Posted by Golden view View Post
I'd sure be curious to see what a blower door test would show on homes here in the PNW. The new homes I built in Alaska tested to around 1 ACH50. And I didn't tape the house wrap.


Howíd you do that...! 1 takes work to get to. Were you exolating?


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Old 02-17-2019, 11:15 AM   #5
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Re: Typical Air Infiltration Rates?


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Howíd you do that...! 1 takes work to get to. Were you exolating?


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I did it all with vapor barrier. 6 mil poly with Tremco at all the seams. Wiring and outlets either inside of the vapor barrier (double wall construction) or meticulously sealed.

exolating?
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Old 02-17-2019, 06:09 PM   #6
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Re: Typical Air Infiltration Rates?


Alaska is famous for the persist and remote wall systems in which all insulation is to the exterior of sheathing plane. Makes a lot of sense aside from the drainage plane fuss and the chemical nature of foam insulation.

http://www.cchrc.org/remote-walls

The double stud, detailed plastic, and detailed penetrations makes sense but your still doing well at 1ach50. You must be focused.

What brand window and door?


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Old 02-17-2019, 08:18 PM   #7
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Re: Typical Air Infiltration Rates?


Quote:
Originally Posted by duburban View Post
Alaska is famous for the persist and remote wall systems in which all insulation is to the exterior of sheathing plane. Makes a lot of sense aside from the drainage plane fuss and the chemical nature of foam insulation.

http://www.cchrc.org/remote-walls

The double stud, detailed plastic, and detailed penetrations makes sense but your still doing well at 1ach50. You must be focused.

What brand window and door?


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The CCHRC has some cool stuff going on. I know the director a little.

Alpine vinyl picture and casement windows. Nothing super fancy.

Now working in Portland, OR, I'm super lazy when it comes to detailing these things. Our homes are just so cheap to heat.
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Old 02-17-2019, 08:19 PM   #8
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Re: Typical Air Infiltration Rates?


I agree with SLS 5-7 seems about right from the research I've seen. For areas that started using poly vapour barriers late 70's early 80's would be around the time that people started trying to use it as the air barrier as well by taping the seams and acoutical sealants. Most regular houses here would be in the 3 range with standard practices.


What exactly are you trying to do with your modelling?
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Old 02-17-2019, 08:44 PM   #9
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Re: Typical Air Infiltration Rates?


I havenít been able to log onto contractortalk through a web browser in years so I canít post my modeling but Iíll try.

My primary goal is to increase performance in the most cost effective way. Iím looking at 2x6 dense pack, 2x6 dense pack with 2Ē exterior foam, and 8-12 inch double stud wall.

I also have comfort metrics based on each zone (room) which helps people understand that wall assembly has a real impact on your general enjoyment of the building.

Iím plugging in different door and window packages and infiltration rates and most importantly designing shading so that the house can be as cool as possible In the summer without running any AC.

These homeowners have spent the last 3 years in a yurt on the property so they are not easy to sell a wall assembly upgrade to!


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Old 02-17-2019, 09:00 PM   #10
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Re: Typical Air Infiltration Rates?


Typical air infiltration rates?-img_3022.jpg

Attached is an image of the 3d model which is used to reference surfaces (to scale) and the script which geolocates the model and has the weather/climate data to apply. Unlike a typical spreadsheet this is tracking the sun throughout the average day and how heat moves through your given wall assembly. Here Iím roughing out the model so I have just 1 zone and highly simplistic materials. You can see Iíve added a door and a few windows.




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Old 02-17-2019, 09:16 PM   #11
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Re: Typical Air Infiltration Rates?


Typical air infiltration rates?-img_3023.jpg

Hereís a graph of heat usage yearly. You can see the building needs some serious BTUs in that first bit of February based on historical weather data.

This building is 38 feet facing south/north, 26 feet east/west.


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Old 02-18-2019, 05:51 AM   #12
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Re: Typical Air Infiltration Rates?


What software are you using for this?

One thing you mentioned, cool in summer without using AC - make sure you are using LEDS & every other trick in the book because a well insulated home doesn't like to give up that heat that is generated inside. Of course being in Vermont where they probably know how to & it makes sense to open up windows helps a lot
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Old 02-18-2019, 08:19 AM   #13
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Re: Typical Air Infiltration Rates?


There's some good resources on GreenBuildingAdvisor.com and some articles on energy efficient homes at FineHomebuilding.com. You might want to check there.

I recall some articles / discussions of a staggered double 2x4 wall being fairly cost effective. If I recall correctly, essentially you have a 2x6" bottom/top plate or larger. Then you stagger the inside/outside studs on the plate edges to eliminate thermal bridging without the use of exterior foam. You can then air seal the exterior sheathing / penetrations.

I assume you are trying to model to figure out the "payback" on the performance upgrades? Make sure you also account for a less quantified measure of improved home comfort (although anything might beat a yurt) and resilience in the face of a storm or power outage.
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Old 02-18-2019, 08:41 AM   #14
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Re: Typical Air Infiltration Rates?


Quote:
Originally Posted by Mr_Stop View Post
There's some good resources on GreenBuildingAdvisor.com and some articles on energy efficient homes at FineHomebuilding.com. You might want to check there.

I recall some articles / discussions of a staggered double 2x4 wall being fairly cost effective. If I recall correctly, essentially you have a 2x6" bottom/top plate or larger. Then you stagger the inside/outside studs on the plate edges to eliminate thermal bridging without the use of exterior foam. You can then air seal the exterior sheathing / penetrations.

I assume you are trying to model to figure out the "payback" on the performance upgrades? Make sure you also account for a less quantified measure of improved home comfort (although anything might beat a yurt) and resilience in the face of a storm or power outage.
I've used the double stud method, except with separate plates. 2x6 exterior 24" OC with R-21, a poly vapor barrier, and then a 2x4 16" OC interior with R-11. Depending on dew point calculations, the interior could be up to R-15. This has more framing cost , but fairly inexpensive insulation. You can even run 4" ducts in exterior walls this way, all inboard of the vapor barrier.
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Old 02-18-2019, 12:48 PM   #15
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Re: Typical Air Infiltration Rates?


Quote:
Originally Posted by Golden view View Post
I've used the double stud method, except with separate plates. 2x6 exterior 24" OC with R-21, a poly vapor barrier, and then a 2x4 16" OC interior with R-11. Depending on dew point calculations, the interior could be up to R-15. This has more framing cost , but fairly inexpensive insulation. You can even run 4" ducts in exterior walls this way, all inboard of the vapor barrier.
Good idea on the separate plates as that will further reduce thermal bridging in the wall assembly. In the lower states, I don't believe poly is recommended anywhere anymore. I believe it is far better to use something a bit more permeable like Certainteed Membrain.
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Old 02-18-2019, 01:35 PM   #16
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Re: Typical Air Infiltration Rates?


Quote:
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Good idea on the separate plates as that will further reduce thermal bridging in the wall assembly. In the lower states, I don't believe poly is recommended anywhere anymore. I believe it is far better to use something a bit more permeable like Certainteed Membrain.


Yes. ďIntelligentĒ membranes have replaced poly for good reason. I mostly use the Pro Clima and PArtel products but there are many out there.


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Old 02-18-2019, 01:46 PM   #17
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Re: Typical Air Infiltration Rates?


Quote:
Originally Posted by Golden view View Post
I've used the double stud method, except with separate plates. 2x6 exterior 24" OC with R-21, a poly vapor barrier, and then a 2x4 16" OC interior with R-11. Depending on dew point calculations, the interior could be up to R-15. This has more framing cost , but fairly inexpensive insulation. You can even run 4" ducts in exterior walls this way, all inboard of the vapor barrier.


The assembly youíre describing ( if I understand you correctly ) is actually pretty high tech. Locating your vapor/air barrier in the middle of the wall assembly allows the wall cavity to dry to both sides and effectively cuts the wall depth in half in regards to moisture build up.

Nice work!


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Old 02-18-2019, 06:39 PM   #18
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Re: Typical Air Infiltration Rates?


Quote:
Originally Posted by duburban View Post
The assembly youíre describing ( if I understand you correctly ) is actually pretty high tech. Locating your vapor/air barrier in the middle of the wall assembly allows the wall cavity to dry to both sides and effectively cuts the wall depth in half in regards to moisture build up.

Nice work!


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Yep, that's pretty much it.
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Old 02-19-2019, 05:09 PM   #19
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Re: Typical Air Infiltration Rates?


Quote:
Originally Posted by duburban View Post
The assembly youíre describing ( if I understand you correctly ) is actually pretty high tech. Locating your vapor/air barrier in the middle of the wall assembly allows the wall cavity to dry to both sides and effectively cuts the wall depth in half in regards to moisture build up.
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)
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Old 02-19-2019, 11:51 PM   #20
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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
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.

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