# the same old question vapor barrier or no vapor barrier



## The Coastal Craftsman (Jun 29, 2009)

I have a customer who has a high end custom home that has been half framed and finished basement. he wants the other half done but here's the issue. i never frame tight to the basement foundation walls. i like to leave a inch or 2 for air flow between the back of the studs and the wall so any damp can dry out. but the previous builders put the framing as tight to the wall as they could and then installed a vapor barrier between the studs and basement foundation wall. 

Its the first time i seen it done like this. The basement has been dry even after weeks and weeks of rain so there's no water getting in the basement but is this vapor barrier a good idea? the issue is i have to continue the framing and its already partly done so he wants me to continue with what they started which means copy what they did. Im ok doing it like this way if its gonna be fine.


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## Tom M (Jan 3, 2007)

Well the vapor barrier is supposed to be on the warm side of the wall to prevent trapping moisture behind the drywall. If they put vapor barrier behind the studs you will be collecting moisture between the studs, add insulation and it will be even worse because of lack of air or drying space.

I like the way you do it but in this case, why not use a rigid foam against the masonry and frame with a narrower profile stud to marry flush with the framing your not changing.


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## overanalyze (Dec 28, 2010)

Your best bet may be exactly what Tom said. I would remove the vapor barrier. If you have to match up with existing walls, use 2" Dow and then studs flat using tapcons to attach. At least 1-1/2" is recommended because then its thick enough to get your dew point away from the foundation. If you have to use stud framing, then use spray foam at at least at 1-1/2". We used to use the fiberglass like you describe they did and we did it with the airspace like you did. Both are less than ideal. 

Our Ohio code now states r-10 minimum for foundations. We use the Dow, glued and taped seams and then add our framing. 

I would simply tell your client that the science behind foundation insulation has changed over the years and this is the new preferred and recommended way.


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## Chad McDade (Oct 14, 2012)

The vapor barrier they have in place will lead to issues down the road. If the home owners are insisting on having the vapor barrier on the masonry side of the wall how about cutting in wall registers every so often to encourage airflow and help keep the wall cavity dry?


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## The Coastal Craftsman (Jun 29, 2009)

Tom M said:


> Well the vapor barrier is supposed to be on the warm side of the wall to prevent trapping moisture behind the drywall. If they put vapor barrier behind the studs you will be collecting moisture between the studs, add insulation and it will be even worse because of lack of air or drying space.
> 
> I like the way you do it but in this case, why not use a rigid foam against the masonry and frame with a narrower profile stud to marry flush with the framing your not changing.




Tom this is how its done so far. 











I have seen it done so that the vapor barrier is on the warm side between the drywall and studs but from what i have read that's bad because it traps the moister between insulation and foundation wall. I don't do any vapor barrier. 

heres what the EPA say

"For example, an interior stud wall erected next to a below-grade basement wall and insulated with mineral wool, fiberglass or cellulose insulation should not have foil-faced paper, polyethylene film or vinyl wallpaper on its interior surface. Water vapor passing from the damp earth through the below-grade concrete or concrete masonry unit (CMU) wall will pass easily through the insulating materials, but accumulate on the backside of a vapor barrier. The entire wall cavity then becomes a cool, damp microclimate. Using materials of 2 perms or more on the interior of the wall allows it to dry into the basement."


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## The Coastal Craftsman (Jun 29, 2009)

ok so the foamula 250 with furing strips looks like it will get me what i need depth wise. But im seeings a lot of people using these boards and adding a vapor barrier on top of the studs between the drywall. The Owens tech guy said if i tape the seams the board will act as a vapor barrier so why on earth are so many people online adding a second vapor barrier!


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## overanalyze (Dec 28, 2010)

BCConstruction said:


> ok so the foamula 250 with furing strips looks like it will get me what i need depth wise. But im seeings a lot of people using these boards and adding a vapor barrier on top of the studs between the drywall. The Owens tech guy said if i tape the seams the board will act as a vapor barrier so why on earth are so many people online adding a second vapor barrier!


Because of either an improperly informed inspector and lack of knowledge on their part. Fill any gaps in corners and at the bottom with can foam and tape the seams. Simple, quick, clean, and you have the backing of buildingscience.com behind you. Its their prefered recommended way for your climate zone.


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## Xtrememtnbiker (Jun 9, 2013)

I'm reading this and trying to come up with what you would do if your block wall is not level. Assuming you are using tapcons to attach flat 2x4's. would you potentially shim between insulation and 2x4 or is there much of way to correct this?


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## The Coastal Craftsman (Jun 29, 2009)

Spoke to a really helpful Owens Corning rep. Really knew his stuff. He said what was done already is def wrong. Which i guessed it was. He said the foam boards even when tape are only a vapor retarder and not a barrier so that's the thing I was worried about. He also said it would be a good idea to add a vapor barrier as you normally would even down here in VA. 

The formed concrete walls in this place seem level and square. The floors are polished like a mirror. They seem to have done a nice job except for the vapor barrier being on the wrong side of the stud wall.


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## overanalyze (Dec 28, 2010)

BCConstruction said:


> Spoke to a really helpful Owens Corning rep. Really knew his stuff. He said what was done already is def wrong. Which i guessed it was. He said the foam boards even when tape are only a vapor retarder and not a barrier so that's the thing I was worried about. He also said it would be a good idea to add a vapor barrier as you normally would even down here in VA.
> 
> The formed concrete walls in this place seem level and square. The floors are polished like a mirror. They seem to have done a nice job except for the vapor barrier being on the wrong side of the stud wall.


I am a little surprised by it only being a retarder. I know with spray foam, the higher density stuff, anything 1-1/2" or more does form its own vapor barrier. A retarder would prob be fine in your application since the foam can't grow any mold and the dew point will occur somewhere inside the foam... good info to know though!


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## The Coastal Craftsman (Jun 29, 2009)

overanalyze said:


> I am a little surprised by it only being a retarder. I know with spray foam, the higher density stuff, anything 1-1/2" or more does form its own vapor barrier. A retarder would prob be fine in your application since the foam can't grow any mold and the dew point will occur somewhere inside the foam... good info to know though!


He said the 2" had permeability of 1 which is more than ply or OSB from what he was saying. He said theres no need to even tape the seams when using the foam on interior situations. He said that's only needed on exterior. half the stuff he said went in one ear and out the other but he got what I needed to know answered.


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## Xtrememtnbiker (Jun 9, 2013)

Walls around here are never perfect. Lol.
It seems like the shims would just compress into the foam though. We have done them with the air space in the past and that makes it where you can level it properly.


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## greg24k (May 19, 2007)

IRC Section R322 specifies that the vapor retarder shall be installed on the warm-in-winter side of the thermal insulation for the above ground installation. 

With that said below grade basement walls differ from above-grade walls in that they are vulnerable to ground moisture wicking into the basement wall. Because of this, the important factor is to maintain the
drying potential of the wall since one never knows if the driven moisture be driven from the inside or outside outside to the inside of a basement floor. 
If foundation wall has hollow cores then air movements within
the wall will also increase the thermal and moisture movement . This is why it is recommended that a vapor barrier will not be used in a wall that is partially or fully below grade. If you got a walk out basement with foundation wall above grade level, then that wall may use a vapor barrier, and it is also depends on the climate.

I also read an interesting article a while back, about suggested airspace between the masonry wall and the stud wall insulation in order to keep the wall dry, and it said that this could actuality make matters
worse if that space exist. 
The reason for it, is that this vertical air space can lead to a convective air loop, which will increase not only the thermal but also the moisture transfer within the wall. If a full height wall is installed in addition to the masonry wall above the ground level, the stud wall is often off-set an inch or so, increasing the depth of the cavity to be insulated . The entire depth of this wall cavity should be insulated and this will also insulate the back of the studs reducing thermal bridging.

If the stud wall is placed on a partially below-grade masonry wall, the stud wall should be insulated the same way as other above-grade walls in the house.


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## Tom M (Jan 3, 2007)

Last week I thought for certain Fish oil was good for me...

Use the rigid foam and eliminate any vapor barrier......I personally think all wall systems should breath with no vapor striction. The tighter we air seal these homes the less of an issue it will be. IMOP


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## SLSTech (Sep 13, 2008)

The key to remember is that wet moves to dry & as the ground outside is essentially 100 saturated... If you manage drainage outside & got the details right, you shouldn't have an issue with moisture intrusion there, but... 

Best product is a delta dry type that goes under the bottom plate & is sealed at the top, allowing any water to drain into a French drain while not allowing any moisture to head directly up to the floor framing / rim joist area. Next best is Closed cell foam sprayed directly onto the wall - preferably you would use foam for the floor if none is under the slab, build your wall an inch or so away & then spray behind it with foam

Plastic is the worst thing you could use in the basement as you will trap the moisture between it & the wall allowing all sorts of things to grow & buildup until they can find away out


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## spartancc (Dec 4, 2011)

Tom M said:


> Well the vapor barrier is supposed to be on the warm side of the wall to prevent trapping moisture behind the drywall. If they put vapor barrier behind the studs you will be collecting moisture between the studs, add insulation and it will be even worse because of lack of air or drying space.
> 
> I like the way you do it but in this case, why not use a rigid foam against the masonry and frame with a narrower profile stud to marry flush with the framing your not changing.


Vaper lock


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## Spencer (Jul 6, 2005)

I know 2 people that actually ripped down strips of 1/2 foam and put them the whole way around the perimeter before the floor was poured and then removed them afterward. This allowed any water that could get through the wall from a crack or whatever to go straight down the wall, through the stone, and into the perimeter tile. Very unorthodox, but interesting.

I would never put fiberglass in a basement. Period. End of story. If that thing ever floods you are ripping all the drywall off because it will suck the moisture up like a wick and won't dry. With spray foam or blue board you can remove base, drill a 5/8" hole in each cavity and use fans to dry things out and you'll be fine.

Closed cell spray foaming basement walls is hands down the best approach I know of. Stud your walls 1" off foundation wall and then foam it. You get great insulation, great moisture barrier, and your stud wall is solid as a rock because it is essentially cemented in place by the foam.

I stock about about 25+ houses a year with drywall and I can't say I ever see moisture barriers in the basements before drywall. In my opinion fiberglass should be outlawed in basements. Probably the only reason it isn't is because it is more profitable to put in fiberglass than spray foam. I find it ridiculous that these insulation guys are getting elected on boards and making it code for a frickin basement to be insulated even if it isn't going to be finished in the first place.


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## The Coastal Craftsman (Jun 29, 2009)

Spencer said:


> I know 2 people that actually ripped down strips of 1/2 foam and put them the whole way around the perimeter before the floor was poured and then removed them afterward. This allowed any water that could get through the wall from a crack or whatever to go straight down the wall, through the stone, and into the perimeter tile. Very unorthodox, but interesting.
> 
> I would never put fiberglass in a basement. Period. End of story. If that thing ever floods you are ripping all the drywall off because it will suck the moisture up like a wick and won't dry. With spray foam or blue board you can remove base, drill a 5/8" hole in each cavity and use fans to dry things out and you'll be fine.
> 
> ...


Every basement I have ever worked in except for one had fiberglass insulation. Dow and OC both say its fine so I would take there advice over almost anyone else. I'm using formula on this job now though.


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## Spencer (Jul 6, 2005)

BCConstruction said:


> Every basement I have ever worked in except for one had fiberglass insulation. Dow and OC both say its fine so I would take there advice over almost anyone else. I'm using formula on this job now though.


Yes, Dow and OC are going to have a completely unbiased opinion being that they are the ones who manufacture this highly profitable product. I will give it to you, it is probably ok in most situations but have you ever delt with a flooded basement that has batts? You are screwed my friend. Get ready for the mold. Not to mention the fact that batts settle and are prone to areas of poor coverage. I have pulled off enough drywall to know what batts do in time.

Here is a little bit of truth that not many people know, the reason you see batts so often is because 

A) Any monkey can install it.
B) It takes no overhead to install it.
C) and most imortantly........it is *PROFITABLE*. 

Insulation contractors, lumber yards, and box stores all love it because there is this little thing called "high margin" when you sell the stuff. That means more profit. Ask any honest insulation contractor and they will tell you the same thing. It gets pushed because there is more money in it. 

Do you want to roll up your $75k foam rig with trained guys to insulate the basement or send out the low paid monkeys to throw the stuff up, meanwhile making money of the low wage labor and high markup material. Every insulation contractor I know of around home and online has said there is no money in spray foam.

2" blue board is a whole different subject.


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## The Coastal Craftsman (Jun 29, 2009)

Spencer said:


> Yes, Dow and OC are going to have a completely unbiased opinion being that they are the ones who manufacture this highly profitable product. I will give it to you, it is probably ok in most situations but have you ever delt with a flooded basement that has batts? You are screwed my friend. Get ready for the mold. Not to mention the fact that batts settle and are prone to areas of poor coverage. I have pulled off enough drywall to know what batts do in time.
> 
> Here is a little bit of truth that not many people know, the reason you see batts so often is because
> 
> ...


If you have a flood the least of your problems is wet insulation. The 2 lower streets to me flooded out all the house basements. They pulled out the drywall and insulation. I would leave the drywall in either even if it had spray foam behind it so taking the insulation out at the same time is easy. for the price the spray foam costs you could insulate with fiberglass 8x over lol.


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## CO762 (Feb 22, 2010)

SLSTech said:


> The key to remember is that wet moves to dry & as the ground outside is essentially 100 saturated...


It is?


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## Spencer (Jul 6, 2005)

BCConstruction said:


> If you have a flood the least of your problems is wet insulation. The 2 lower streets to me flooded out all the house basements. They pulled out the drywall and insulation. I would leave the drywall in either even if it had spray foam behind it so taking the insulation out at the same time is easy. for the price the spray foam costs you could insulate with fiberglass 8x over lol.


If you get water in the basement the greatest concern is getting things dried out before mold can develop. If the water is removed quickly enough drywall can be fine.

I do insurance work through a floor cleaning service. When a basement has water issues for whatever reason they call me, a trim carpenter. Why? Because I can pull all the baseboard off and put it back on again. When a basement gets water I go in and pop it off. Then drill 5/8 holes in the center of all the wall cavities behind the base. Carpet cleaner brings in a bunch of fans and is able to dry it out as long as no batts.

We aren't talking flooding here. 

Sump pump goes out.
Pex fitting bursts.
Wife leaves the faucet on.
Toilet over flows. 
Water spigot in utility room left on.
Sump can't keep up because of too much rain.

I did an insurance job for a family last year who actually had a basement that drained to daylight because of high elevation. No sump pump needed. Somehow there was a storm and the water wasn't draining and they couldn't scramble fast enough to get pumps. Was probably an animal that crawled up the tile and plugged it. Never did figure it out. Luckily they had blue board and no batts.

Any of the above can happen while you sleep or are away for the weekend leaving you screwed. Not worth it. Doesn't take a flood.


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## jegra45 (Aug 5, 2013)

BCConstruction said:


> He said the 2" had permeability of 1 which is more than ply or OSB from what he was saying. He said theres no need to even tape the seams when using the foam on interior situations. He said that's only needed on exterior. half the stuff he said went in one ear and out the other but he got what I needed to know answered.


actually you are right about foam board. but if I correctly remember spray foam (urethane) is a vapor lock. 
I mostly use 2 inch isofoil(brand) foam panel that have a aluminium sheet over it when I need to insulate basement. wich you need to to tape if you want it to be a vapor lock. 
in my opinion
spray foam is the best insulation for basement, but it's less cost effective ^^


I had the exact same problem (vapor lock on concrete wall with fiberglassover it) with a client 2 year ago.
I needed to prove to the client that he should not keep it like this.
I live in canada so my point was easy to prove :thumbsupyou'll understand quickly)

the temperature outside was about -25 degree celcius.(-13F)
I remove a windows trim to be able to reach behind the fiberglass
took a paper towels and pass it on the vapor lock.
the towel was soaking wet... the client was convinced.


in conclusion, the best cost-effective solution for basement insulation
is 
spray foam on the end joist and foam board on the concrete.
in my short working experience :whistling

sorry for my english, it is obviously not my first language ^^


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## Spencer (Jul 6, 2005)

jegra45 said:


> actually you are right about foam board. but if I correctly remember spray foam (urethane) is a vapor lock.
> I mostly use 2 inch isofoil(brand) foam panel that have a aluminium sheet over it when I need to insulate basement. wich you need to to tape if you want it to be a vapor lock.
> in my opinion
> spray foam is the best insulation for basement, but it's less cost effective ^^
> ...


Same thing happened to a friend of mine. Wouldn't listen. Put fiberglass in trying to save money. The very morning the drywallers were coming to start hanging the basement one of the batts falls down. They were all wet on the backside. They all got jerked out and he foamed.


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## The Coastal Craftsman (Jun 29, 2009)

Well I'm even more confused than I was before after speaking to techs from both Dow and Owens Corning. 

Here's what I have found out now 

Dow foam board 
Acts as a vapor barrier on the unconditioned side
can be used in combination with fiberglass

Owens Corning 
Does not act as a vapor barrier 
Can be used with fiberglass
needs a vapor barrier on the conditioned side

They are doing a due point analysis to finger out the best layout for what I need. 

I hoping that I can do 1" foam board, stud wall with fiberglass then drywall. This is based on Dows product. 

They both said fiberglass is ok as long as a true vapor barrier is used on the conditioned side.


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## Spencer (Jul 6, 2005)

I would be very interested if you find anything about how a dew point is moved by adding or not adding a vapor barrier.

On the above ground levels of my house I did closed cell spray foam and then blew wet cellulose. I was told by my insulation guy that if you put visqueen on the drywall side it will move the dew point to the visqueen and that if I did that he would ring my neck. 

I have no idea what is different about closed cell + fiberglass vs. closed cell + cellulose but they are recommending completely different things and I know it all comes down to dew point.


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## Tom M (Jan 3, 2007)

The code is going to tell you that a vapor barrier be used on the warm side of any construction so that advice should be consistant.

Dow has many products. If its straight up blue foam then it is still vapor permeable. If its Polyiso then its foil face is not permeable and is considered a vapor barrier. There are all kinds of triggers including conditioning the space but the main goal should be to elminate any air flow to a cold surface. Thats why R-10 is so widely advised.


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## Spencer (Jul 6, 2005)

Tom M said:


> The code is going to tell you that a vapor barrier be used on the warm side of any construction so that advice should be consistant.


IMO putting blanket statements over everything like that is a good recipe to get sued. Climates are different and the basement space is a completely different climate than the floors above it.

Put a vapor barrier on the warm side on a basement is completely different than above ground. Reason being the concrete basement wall is going to be prone to moisture penetration from the outside, number two, basement wall is going to be cool at times, thus more prone to condensation forming because the wall temperature can be lower than the dewpoint at certain times. 

In theory, with a properly installed vapor barrier you would stop the migration of moisture from the interior to the inside of the wall cavity, as well as from the wall cavity to the interior but guess what, you're screwed because all the moisture is now trapped on the inside of the cavity. Are you counting on moisture breathing to the outside? Hope not.

Best method is to stop moisture from penetrating from the outside. Whether it be from closed cell spray foam (open cell is a sponge) or blue board whether it be rated as a vapor barrier or vapor retarder. This will keep the bulk of the moisture out but the wall cavity still needs to breath to prevent mold/moisture buildup, yes it needs to breathe to the inside. Remember you have already stopped most of the moisture at the outside wall. Installing a *double* vapor barrier or retarder is a bad idea in most situations.

Fiberglass is a mold playground if there is moisture present. It might be acceptable with polystyrene behind, but if you sandwich that stuff between two vapor barriers and you are asking for it my friend. Bring on the mold.

The reason code says to put the vapor barrier on the inside is because you want to keep the barrier temp above the dewpoint. Put the barrier on the cold side and you get condensation. The rule doesn't apply to situations where there should be no barrier.

If you don't take it from me take it from the inspectors themselves...

http://www.nachi.org/forum/f18/poly-being-applied-basement-walls-26852/


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## jtmorrow (Jan 30, 2014)

I didn't see any mention of using Roxul instead of fiberglass. Water will drain right through Roxul without decreasing the R value and will not mold. I used 2" SM on the walls with 2x4 stud wall, R14 Roxul inside of that, no vapor barrier as taped SM is vapor barrier.

Spray is very expensive in my area as only 1 installer and no competition.


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## fjn (Aug 17, 2011)

This may help . I would go to Building Science Corp. web site and look at the three books they have as builders guides. One is for cold climates,one for hot, and one for intermediate. The book that is most appropriate for your zone will present the best approach for you to utilize. The reason for the three books,each climate zone has different requirements as to where the barrier goes if at all.


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## fjn (Aug 17, 2011)

Here is the most recent editorial from JLC on the subject.


http://www.jlconline.com/moisture-barriers/lessons-in-building-science_o.aspx?dfpzone=general#


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## MarkJames (Nov 25, 2012)

Spencer said:


> If you get water in the basement the greatest concern is getting things dried out before mold can develop. If the water is removed quickly enough drywall can be fine.
> 
> I do insurance work through a floor cleaning service. When a basement has water issues for whatever reason they call me, a trim carpenter. Why? Because I can pull all the baseboard off and put it back on again. When a basement gets water I go in and pop it off. Then drill 5/8 holes in the center of all the wall cavities behind the base. Carpet cleaner brings in a bunch of fans and is able to dry it out as long as no batts.
> 
> .


Those 5/8" holes and fans are enough? Sounds like it wouldn't quite dry out on the backside. How many days are the fans running? How do you check the backside for compete dryness? Thanks.


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## GettingBy (Aug 19, 2010)

This is getting pretty complex \/




"The cfm50 is a number that makes sense to analysts who work with it all the time, but when a homeowner hears that their house leaks at the rate of 4500 cfm50, for example, it usually doesn't make a lot of sense to them. Also, larger houses have more places that can leak, so you can't directly compare the cfm50 for different size houses.
So, once the auditor/rater has the cfm50, they usually do some calculations to present the results in ways that are easier to grasp and that eliminate (or at least reduce) the issue of house size. The first and most common calculation is to convert cfm (cubic feet per minute) to ACH (air changes per hour). An air change is when a volume of air equal to the volume of the house exchanges with outside air. One ACH, then, means all the air in the house exchanges once per hour.
With the Blower Door running and the house pressure at negative 50 Pascals, a typical existing home might leak at the rate of 15 air changes per hour, which is written 15 ACH50. Really tight houses can get down to 1 ACH50 or even less. In fact, the Passive House program requires a maximum infiltration rate of 0.7 ACH50."
and
"1 Pa (Pascal) = 0.000145037738 Psi (Pound Per Square Inch)"

Have fun converting this to inches of water column.


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## Spencer (Jul 6, 2005)

MarkJames said:


> Those 5/8" holes and fans are enough? Sounds like it wouldn't quite dry out on the backside. How many days are the fans running? How do you check the backside for compete dryness? Thanks.



I'd say fans run about a week normally. 

They have moisture meters they test with. I think usually they do a decent job of getting thing dried out because if they don't it's a liability for them.


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## SLSTech (Sep 13, 2008)

GettingBy - actually whoever wrote that needs to be smacked
For example Passive House is .6 ACH

ACH is an artificially created number that most houses will not deal with normally - so 15 ACH does not mean that a house will normally exchange that much air in a normal hour. Next those number conversions do nothing to eliminate the small house penalty - the only one that does some what it the ELR

As for converting Pascals to inches of water column... 25 Pa (duct testing)--- 50 Pa (air-leakage / duct testing in some North West areas) --- 75 Pa (military testing) 1 in H2O = 249 Pa0.100.200.30

Spencer - 5/8" holes, I take it they are running tubes into those to force air into the cavities? Like MarkJames I can't imagine the holes by themselves would be close to enough


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## rrk (Apr 22, 2012)

I can tell you here at least those 5/8" holes don't do squat. Servicemaster used to do that and it did not work at all. I went to install a pocket door in a room where it was done and the wall was full of mold. It was 2 years after the flood and they came back and had to remove all of the drywall. It became a huge ordeal with lawyers and hotels involved.

5/8" holes and a week is nothing.


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## Spencer (Jul 6, 2005)

SLSTech said:


> Spencer - 5/8" holes, I take it they are running tubes into those to force air into the cavities? Like MarkJames I can't imagine the holes by themselves would be close to enough





rrk said:


> I can tell you here at least those 5/8" holes don't do squat. Servicemaster used to do that and it did not work at all. I went to install a pocket door in a room where it was done and the wall was full of mold. It was 2 years after the flood and they came back and had to remove all of the drywall. It became a huge ordeal with lawyers and hotels involved.
> 
> 5/8" holes and a week is nothing.


I'm just the guy they call to take the baseboard off and put it back on. But I can tell you that is exactly what they do. Keep in mind this only applies to situations with spray foam or blue board. Fiberglass is a wick, everything gets ripped out with fiberglass.

They don't call me anymore because I'm to expensive I think. But in the past, the base is removed, then they put a boat load of carpet fans and commercial dehumidifiers down there. I think a week is a pretty normal time span.

They test everything with moisture meters before they pull their equipment out. It has to pass be under x number I assume.


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## zp6 (May 6, 2015)

*spray foam always*

I'd spray foam those walls 2-3.5 inches for r21 and then you know its sealed secure and safe. we had a massive flood here in calgary the other year and now every single house that flooded has been redone in spray foam. 
Here in our district in canada its code that the studs must be an inch off the wall, the installed batts cannot be against the walls and a vapor retarder must be in place on the warm side of the batts only.
Also here in canada we're no longer using the term vapor barrier,only vapor retarder as per the can/ulc listings. 2 inches of closed cell(2lb) spray foam gives you your vapor retarder and should never be covered with another layer of poly.


The mormons here wanted their new church/monument to last for a thousand years so we spray foamed the entire thing. It's gonna last far past that for sure. How long do you want your house to last for?


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## GettingBy (Aug 19, 2010)

zp6 said:


> How long do you want your house to last for?


Half the people move within 7 years, almost all within 14.


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## GaryEvans (May 13, 2015)

Building code in Canada requires R12 for below grade basement walls.

And like many of you have said there's different ways of doing this and at different costs.
The best is a professional spray foam installation with the studs at least 1inch off the concrete wall.
But this is very expensive, most people will not spend that much extra money.
2nd best, Rigid foam......products similar to Styrofoam SM.
But I would still install a 6mil vapor barrier on the warm side of the styrofoam. 

By far the most common is fiberglass insulation because it's much less expensive but can create problems like the ones we've been talking about.
Almost everyone has a budget for renovations, we shouldn't forget that.

If your using fiberglass then I recommend keeping the studs 1-2 inches off the concrete wall, install a breathable barrier like an exterior house wrap on the concrete side of the stud wall as your standing the walls.
This will help protect the insulation and keep it from contacting the concrete.
Install the 6mil vapour barrier on the warm side of the insulation.

And always use a treated sill plate for all the basement walls that come in contact with the concrete floor.


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