Proper vapor barrier?

[Carl A. Brown]

Originally Posted by cbrown1
No way should a horizontal joint be taped on any moisture barrier!
What if the top piece of sheathing membrane overlaps the lower one properly?

There is a detail I have where there is a horizontal slit is made in the housewrap over the window and the vertical leg of the drip cap/window Z flashing is inserted up behind the wrap and then the flashing/wrap joint is taped horizontally it should not be taped all the way along the flashing just a spot here and there.

When they install their flex wrap in the sills of openings it is reverse lapped on the sides.

All moisture barriers need to over lap all flashings to exit the water to the exterior of the cladding.

I have gone round and round with the reps here in town.

They have even told me if the wrap is on reverse lap just tape it and it will be fine!

[David P. Valley]

Originally Posted by Brian A. MacNeish

If it is on the outer side of the insulation, how can it be on the warm side of the building?

Well. it's pretty simple if you ask me. It doesn't take much brain matter to figure this one out.

When you purchase faced (vapor retarder) insulation blankets, the paper retarder is always on the outside of the roll. Right?

Well, when you go to insulate a building cavity, this outer vapor retarder is then placed against the warm side (inside) of the building, which is the most inner side of the studded cavities (in my area).

Sound logical? DUH....

[Brian A. MacNeish]

Originally Posted by cbrown1

Originally Posted by cbrown1
No way should a horizontal joint be taped on any moisture barrier!
What if the top piece of sheathing membrane overlaps the lower one properly?

There is a detail I have where there is a horizontal slit is made in the housewrap over the window and the vertical leg of the drip cap/window Z flashing is inserted up behind the wrap and then the flashing/wrap joint is taped horizontally it should not be taped all the way along the flashing just a spot here and there.
Why do you say that? Here, as good practice, the exterior wraps are also made into an outer air barrier to help maintain the R value in wall cavity insulation.....so every joint should be fully taped (and properly overlapped for drainage).

When they install their flex wrap in the sills of openings it is reverse lapped on the sides.
Are they installing Flexwrap up the sides of the window opening also or just the wrap? IMO, just using Flexwrap on the sills is a partial job.


All moisture barriers need to over lap all flashings to exit the water to the exterior of the cladding.

I have gone round and round with the reps here in town.

They have even told me if the wrap is on reverse lap just tape it and it will be fine!
What do they know about building science, common sense and good practice??

Unless people have seen the consequences of standard or poor practices, they will not understand what some of us are saying!

[Brian A. MacNeish]

Originally Posted by Richard A. Hetzel

The sentence is badly wriiten, but I think they mean the "outer surface" of the insulation itself, which is, of course, to be installed on the winter warm side of the wall or assembly.

Can't leave any doubt in technical writing!! Wouldn't you agree?

[Brian A. MacNeish]

Originally Posted by dvalley

Well. it's pretty simple if you ask me. It doesn't take much brain matter to figure this one out.

When you purchase faced (vapor retarder) insulation blankets, the paper retarder is always on the outside of the roll. Right?

Well, when you go to insulate a building cavity, this outer vapor retarder is then placed against the warm side (inside) of the building, which is the most inner side of the studded cavities (in my area).

Sound logical? DUH....

David:

This old style of insulation hasn't been sold in Canada sincde the late 1970's-early 80's as the kraft paper vapour retarder was virtually useless in preventing moisture movement into walls. Also, it added extra cost to the product. SO I assumed you were talking about unfaced fiberglass batts.

From your post:
A vapor barrier is a material (typically plastic), that resists passage of moisture through wall, ceiling and floor assemblies of buildings. It is used to separate an environment which is at a high vapor pressure from an adjacent one at a lower vapor pressure.

A vapor retarder is the material on the outer side of insulation. It helps control the amount of moisture passing through the insulation and collecting on exterior walls, ceilings and floors. In my area, this retarder goes on the warm side of the building. In hotter climates, this material goes on the most outer

Don't take it so hard when you make a technical gaff!! Notice how your text (I selected in in blue) says the same thing for both retarders and barriers!! You've got the concepts confused!!

Your "vapour barrier" example of plastic is simply one of the better retarders if thick enough and not a barrier!!! Vapour retarder is the more correct term for all the low permeance products,,,,,unless you have very thick foil or sheet metal......then you have vapour barrier.

Anyways, to talk about vapour retarders .....or barriers..........except as a moisture barrier over soils of crawl spaces is missing a big point....one that I have mentioned here numeous times only to have the "old paradigm " people continue to challenge new information. In walls and ceilings, the big moisture movement issue is uncontrolled air leakage.........infiltration and exfiltration. It has huge implications for energy use also.

From the reference Marcel posted today:
http://archrecord.construction.com/r...onttyvek-4.asp

"Experts estimate that the amount of moisture vapor transported by air currents can be 100 to 200 times higher than the amount transported by vapor diffusion, and can account for more than 98 percent of all water vapor movement through the building enclosure."


SO if you put an unsealed vapour barrier in a wall, it will be stopping maybe 1-2% of all moisture movement.......you may as well leave it out and try to make the gyproc or other wall finish system air tight......it'll stop way more moisture movement.......and condensation.


From a 1975 Canadian NRC Division of Building Research "Digest":
"Air leakage is now considered to be the prime cause of most condensation problems in walls and roof spaces. If, therefore, a building can be made tight against air leakage it may not need a vapour barrier, as defined. On the other hand, if there are openings that permit air to leak from the warm side to the cold side of the insulation, adding a vapour barrier (even of zero permeance [....a perfect barrier- my comment]) that does not seal off the openings will be useless."

AIR TIGHTNESS!! AIR TIGHTNESS!! AIR TIGHTNESS!!

I don't know why the US has been so slow in adopting air tightness criterea in residential codes. From the above referenced article:

"The 1995 National Building Code of Canada (NBC code) requires a continuous air barrier for all commercial (and residential; my edit) buildings. Massachusetts was the first state to adopt an energy code, in 2001, which is similar to the NBC code, and requires a continuous air barrier for commercial buildings. Wisconsin adopted an energy code in 2003. Minnesota is developing an energy code in early 2006, with similar compliance criteria as the Massachusetts energy code. In addition, as of 2003, the Envelope Design Guidelines for Federal Office Buildings and Multi-Family High Rise Residential Buildings require air barriers."

Note: The first house I tried to make air tight was in 1977.......a passive solar home for a couple of veterinarians. About 10 weeks ago, I ran into their "early 30 something" son as he was doing a blower door test as part of an ECO-action energy audit in the nearby city I work out of. Turns out the solar home and his parents green philosophy headed him towards energy conservation and efficiency. He's now a nationally certified auditor and has done well over 6000 audits in 3 different provinces.

[Carl A. Brown]

I have gone round and round with the reps here in town.

They have even told me if the wrap is on reverse lap just tape it and it will be fine!
What do they know about building science, common sense and good practice??



So it is the sales reps that are retarded?

[Brian A. MacNeish]

Originally Posted by cbrown1

I have gone round and round with the reps here in town.

They have even told me if the wrap is on reverse lap just tape it and it will be fine!
What do they know about building science, common sense and good practice??



So it is the sales reps that are retarded?

No, those that train them!! And then the sales force tell architects, contractors, and building supply dealer staff the wrong or poor info and voila......you have failing buildings.

It's gotten so I don't even like caulking as a moisture control measure. Lap everything so that water runs off it at each outer layer of the building- the siding and..... the weather resistant barrier/sheathing membrane behind the rainscreen!

I don't know if you've heard of the British Columbia "leaky condo" fiasco. In the last 15-20 years, it has cost at least $1 billion and possibly $2-3 billion in fixing badly built dwellings. BTW, the Home Warranty Program quickly went bankrupt as it only had about 35 million in its coffers. Here's a now 10 year old report: http://www.qp.gov.bc.ca/condo/letter.htm . I have since seen a short TV piece on leaky highrises in Vancouver!!

Quote from an investigating engineer:
"I think it should be called the "rotten-condo problem, not the leaky-condo problem. There is a difference. Wood does not rot because it gets wet. It rots when it stays wet."

From the report's Executive Summary:

"However, climate and economic pressures do not account for the magnitude of the problem. The residential building process and building science issues have led to a disintegration in the quality of construction.

1. The Building Process
The residential building process operates within a set of complex business relationships, statutes, and regulations. The Commission was presented with case after case of ineffective regulation regarding responsibility and accountability at each stage of the construction process. These included:

(i) an inability on the part of municipalities to effectively monitor building quality; to ensure inspectors play a meaningful role in maintaining building standards and in enforcing building codes;
(ii) a lack of provincial monitoring to ensure accurate interpretation of the building code, as well as its performance requirements;
(iii) a lack of developer, builder, and general contractor responsibility -- often facilitated through protective corporate structures;
(iv) architects who have been unable to maintain professional responsibility in translating designs into quality physical structures;
(v) engineers who have been unable to ensure their involvement in the process will lead to quality construction of the building envelope;
(vi) a lack of training, skills, and qualifications that have led to a deterioration in the quality of worker performance;
(vii) an inadequate home warranty program which, in the majority of cases, is faced with a conflict of interest between its service to the homeowner and its obligation to the developer;
(viii) a mortgage guarantee system which tends to serve the interests of the residential construction industry and financial institutions, without due regard to the consumer, who buys its services;
(ix) a lack of information from the builder to the strata council to facilitate its responsibilities; and
(x) a lack of understanding as to the roles and responsibilities of strata councils and management companies, which has often left the homeowner confused and alone.

2. Building Science
In addition to economic pressures, climatic conditions, and a systemic failure of the building process, building science also played a role in bringing about this crisis of confidence. The factors related to technology, or building science, include:

(i) a poorly interpreted building code;
(ii) municipal by-laws that can lead to inappropriate design, exacerbated by architects, who do not understand the implications of their designs;
(iii) the use of new materials without an understanding of how they will be affected by our climate;
(iv) a loss of collective memory, and lack of conventional wisdom, among inspectors, architects, engineers, developers, and contractors regarding the requirements for effective building; and
(v) ineffective communication and transfer of knowledge among the professionals and business people (who understand the issues), to others involved in the building process.



IMHO, others involved in the building process often do not want to learn new information as it requires time and money to learn/re-learn and interferes with $$$$$ making process!!

[David P. Valley]

Brian,

With the way you continuously argue your points here, I'll bet you were divorced several times in your lifetime.


You are talking Canadian terms, I'm talking East coast terms.

Also, I don't come here to argue my points. I have way too many things to do in my life than to make ridiculous comebacks and act like a child. I simply make my statements on this board and the readers of the threads can either heed them or simply argue their points like you do.

I'm done with this thread. Bye....

[Brian A. MacNeish]

Originally Posted by dvalley

Brian,

With the way you continuously argue your points here, I'll bet you were divorced several times in your lifetime.
Nope......31 years with the same mate.


You are talking Canadian terms, I'm talking East coast terms.
Canada has an east coast also...and it snows and rains here with some horizontal wind driven rain....same as Mass.


Also, I don't come here to argue my points. I have way too many things to do in my life than to make ridiculous comebacks and act like a child.
Quoting you:
"It doesn't take much brain matter to figure this one out."
"I'm done with this thread. Bye....." (I'm taking my toys and going home. I don't like this party!!)

I simply make my statements on this board and the readers of the threads can either heed them or simply argue their points like you do.
Check their correctness with building science experts like Building Science Corp of Westford, Mass. Oh right! Joe Lstiburek doesn't seem to rate in your book!

I'm done with this thread. Bye....

Bye-bye.........!!