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Old 01-04-2012, 04:22 PM   #16
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EPS or XPS


Quote:
Originally Posted by Jeff0101 View Post
Just to be clear folks, the direction I've received is that the vapour barrier is to go on just before the drywall
That's what we are cringing about...there are alot of studies and scientific evidence out there supporting that this is generally considered a bad idea when address below-grade concrete/masonry walls. Above grade is a whole different animal. But, if your local official has you hog tied, then I digress...

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Old 01-04-2012, 04:55 PM   #17
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Page 59, #6.2- conclusions from an article dated ’07; ftp://ftp.cmhc-schl.gc.ca/chic-ccdh/..._Web_sept5.pdf

Check out- ‘Field study” pp. 2: http://docserver.nrca.net/pdfs/technical/317.pdf

A good read, especially “Conclusions” on pp.22; http://www.buildingscience.com/docum...ent-insulation

Jk, now they are messing with my mind………… check it out; http://www.buildingscience.com/docum...study-analysis Notice the vapor barrier and foil-faced polyiso?


Kind of shoots the whole v.b. thing in the foot, at least for me......


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Old 01-04-2012, 04:58 PM   #18
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Oh, sigh... Our city building dept still mandates visqueen above grade, much to the discomfort of a few knowledgeable builders. And then one of the local engineers claims that the HRV's are causing mold problems. Interesting. He may be right, but I can't buy it. Warn the local authorities, and in the event that you get mold/rot, sue 'em. You'll likely be OK with the visqueen, though, as it apparently is working in your environment.
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Old 01-04-2012, 06:52 PM   #19
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Gary: Thanks for the links. I will try to get more "into" them soon. As for the Canadian one, I am confused. Here is what I have to say about what I've read so far, and it does not seem to, in general, necessarily support the use of visqueen, IMO. My comments and questions are after the bullets.


Pg 6, 2.2.2: Water penetration into a wall or solar heating of saturated absorptive cladding will
increase the potential for mold growth on interior drywall finishes if the polyethylene is removed. Polyethylene has been found to protect interior drywall even where studs had rotted and corroded from water ingress. •• No kidding? Glad that sheet rock was protected! I’d hate to lose it when the house fell down. Sarcasm aside, I would wonder if the wall would maybe have dried out if the vb were not obstructing its movement.

a) Building Research Establishment, UK (1989) (As referenced in 2005 by
Derome & Huang): It was stated that removing the vapour barrier should
not be considered since summer condensation could occur behind low-permeability interior finishes. •• What am I missing here? So you want the vb to stop the water in the wall instead of at the “paint”. WTH? Again, why not let it through with low perm paint?

b).... and that the importance of proper vapour retarders as well as air barriers should not be underestimated. •• Key words; retarders, air barriers.

It is suggested that omitting polyethylene vapour barriers may result in increased condensation problems due to air leakage. This may be true unless the industry can rely on contractors to make other layers airtight. •• So, AIR seal. Duh!

e) ...where leakage led to... •• So stop the air leakage.

g) It is concluded that the internal wall must have sufficient vapour resistance to prevent
condensation and reduce risks for mold growth. •• Vapor resistance prevents mold? WTH? Or maybe the wall was permeable enough to let the vapor out? This conclusion seems like it was not necessarily arrived at scientifically, or I am just confused.

Computer modeling predicts that the removal of the vapour barrier can significantly increase the moisture content of the interior gypsum board facing. •• Why is the water coming from the outside, and why is it not passing through? I’d sure like to know if there was a ventilated rain screen and WRB on these walls. Maybe that info is in the details, and I’ll try to read more later. For now, I quit and read the Conclusions.

Conclusions: This part struck me: 6.3, Further Work: This research suggests that interior vapour control at the lower portion of the basement wall is unnecessary or inhibits drying. Code officials should be informed about the results. Changes to codes and construction practice are likely. Permeability in the below-grade portion of the basement wall can be advantageous and should be explored further.

I do not read this paper as doing much to support the use of visqueen below grade, and it leaves a lot of wiggle room for its use above grade. The references to “better air sealing” seemed to overshadow any benefit assumed to the visqueen. Further, I did not see where they demonstrated that “this well air sealed wall w/ visq outperformed this well air sealed wall w/out visq”. I think that anyone using this as a “proof” that visq is necessary, or even useful, is stretching their imagination. Sorry, but I just don’t see it, and I freely admit my bias to not liking visqueen, despite its apparently working in my own house (above grade). So, someone who is in favor of visqueen below grade read this and give us your interpretation. thanks. j
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Old 01-06-2012, 01:39 PM   #20
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One other small issue is that I have some odd angles in the basement corners, and in one corner the builder left a piece of wood, probably from the forms, embeded in the poured cement. No way I can extract it. Looks like a 1x3 or otherwise is just surface wood that stayed after the form was pulled off. I'm thinking I will just entomb it in.

As for the EPS, I will stick with it. The topical range of answers on all the blogs and chat rooms is mind boggling, and although it provides deep understanding, does not eliminate the use of EPS, the type I am using, and in many knowlegable cases, supports the use of EPS.

***Good vapour barriers, dry environment, low humidity control, great drainage outside, seem to be the overriding basics, and if they are all covered, you can use any of the consumer grade products if you construct approriately. Those are my conclusions, for what it's worth.

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Old 01-06-2012, 02:05 PM   #21
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It would be interesting to see why a vb is apparently mandated in Canada when the CHMC (CMHC? whatever) report concludes this "e) This research suggests that interior vapour control at the lower portion of
the basement wall is unnecessary or inhibits drying", which seems in agreement with the BS report. Ask a local official, if you don't mind, and report to us. There must be other information they are using to make that decision. Thanks.
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Old 01-06-2012, 02:21 PM   #22
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Yes, I will have a long discussion with the inspector when he is here on site about all this. They typically get a lot of criticism, but I have found them actually to be well informed, at least the ones I have dealt with. I haven't always liked what they said, but I haven't been able to proove any of them wrong...in the past.

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Old 01-06-2012, 02:34 PM   #23
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Good to hear they are reasonable people, being in a position of authority. Let us know what "the rest of the story" is. Thanks. john
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Old 01-06-2012, 08:18 PM   #24
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Thanks for this thread...very interesting. I'm also in ON and it's good to see advice being thrown around for our climate instead of the southern parts of the US.

I always thought 2" of XPS against the slab taped and foamed tight was recommended. Then build the wall in the normal way with no VB. This allows the wall to dry to the inside. Is this not recommended practice anymore?
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Old 01-06-2012, 08:37 PM   #25
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I'd say the floor is a different matter. But on the walls: If you use XPS of at least 1.5" you can tape it and do away with the vapour barrier, depending on two things; what other additional insulation you may be using, and what your building dept says. It is the multiple insulation products which can cause some issue. If using EPS, don't seal the joins, and do use a vapour barrier. All that being said, your specific basement environment also maters. If you have water infiltration, don't build until you have it resolved.

On the floor, I'll probably use Tyroc. Made in Canada from rubber and recycled plastic, indestructable from water, provides a thermal break, and is inorganic, which on a floor is Gold. Sold at Home Hardware stores. Both Barricade and Dricore have that sheet of OSB which is organic. It worries me. Tyroc, no worries. Tyrocinc.com.

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Old 01-06-2012, 09:13 PM   #26
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Pete: Have you done a heat loss analysis yet? That is #1 on the list. Depending on what your HDD (heating degree days) and local soil temps are, you may want to consider using a LOT more foam under your slab than 2". What is "recommended" is often tradition. Some folks up here still say 2" of foam is adequate, and I guess that depends on what "adequate" means to you. I will be using 10" under the slab, and 12" under and outside the footer (edge beam, whatever you want to call it). A very knowledgeable builder here is using 12" of eps and pouring an 8" slab on top of that, then building. Ten to twelve inches may be excessive for you, but I imagine 2" is a bare minimum (ie, code). Just a thought, but a slab is cold 365 days/year, whereas a wall gets heated part of the time. Lots of energy goes out through a slab if it is not slowed down. Just a thought.
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Old 01-06-2012, 09:27 PM   #27
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I was talking about inside between the poured wall and the studs. Maybe I misread everything in this thread
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Old 01-06-2012, 10:06 PM   #28
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pete: you're good. i misinterpreted what you said. sorry about that. it still may be worth looking at 4" inside.
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Old 01-07-2012, 09:32 PM   #29
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So, it appears none of you have looked at or read about what is behind door #3, 4, or 5? From the last one I sited...... Plastic inside, foil-faced foam inside.....

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Old 01-08-2012, 12:16 AM   #30
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Gary: I looked at options 3, 4 and 5; increasing order of "good". I saw what I saw in the Canadian study, but maybe I read too fast (or don't retain much....). Poly is not such a good idea, for one. What were you seeing in all this?

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