House Wrap

[lolsen]

I have asked some people and have never gotten a consistent answer.

Does House Wrap stop or minimize air infiltration?

Your comments please

Thanks
Lawrence

[jkogel]

Originally Posted by lolsen

I have asked some people and have never gotten a consistent answer.

Does House Wrap stop or minimize air infiltration?

Your comments please

Thanks
Lawrence

It lets air out without letting water in, AFAIK.

[Jeffrey R. Jonas]

Here is a link to DuPont/Tyvek... http://www2.dupont.com/Tyvek_Construction/en_US/

And Owens Corning/PinkWrap data sheet... http://www.owenscorning.com/around/i...fs/19731-D.pdf

[David A. Andersen]

There are several types of barriers. Air, moisture, vapor.

Unless it is an air barrier, No.

What product are you talking about?

[lolsen]

Thanks for the replies

Looks like Tyvek claims to prevent moisture to enter the house, prevent air from going into the house and it lets out moisture.

David
The Tyvek or similar is what I was referring to

Thanks
Lawrence

[David A. Andersen]

Tyvek is NOT the product to use over OSB because the surfactants in the adhesives actually break down the surface tension of liquid water which is what in fact is what makes Tyvek 'waterproof'. Lose the surface tension of liquid water and Tyvek is really no water proofing barrier at all.

[Carl A. Brown]

David,

Where did you get the info in post #6

Thanks Carl

[Larry D. Kage]

Originally Posted by cbrown1

David,

Where did you get the info in post #6

Thanks Carl

David is correct. We studied how surfactants effect the water resistance of house wraps in the FLIR/ITC Building Science Applications IR Thermography course where Scott Wood, the instructor, discussed it. Under certain conditions the added water penetration reduces the OSB to “vertical mulch”.

http://www.umass.edu/bmatwt/publications/articles/housewraps_feltpaper_weather_penetration_barriers. html
There was speculation that surfactants (soaps) could make housewraps more water permeable. And we found this to be true. Surfactants, which break down the surface tension of water, making it flow more easily, are present in soaps and oils that can be found on the surface of construction materials and hands of installers. This may be significant since people regularly powerwash their homes, perhaps making them more likely to leak. Also, cedar and other wood sidings contain water soluble extractives that are thought to act as surfactants. Paints and stucco have surfactants as part of their formulation too. So surfactants seemed like an interesting thing to investigate.
We ran a series of hydro tests using soapy water and then another series using a cedar-extractive solution. We limited our tests to Tyvek, R-Wrap and Felt, since these were the winners of the first round of clean-water tests. Tyvek and R-Wrap lost about 10% of the soapy water column in 2 hours. Felt seemed unaffected by soap, still loosing 30% of its water. Tyvek and R-Wrap lost about 3% of the cedar-extractive mix in 2-hours, while Felt again lost 30%. It does appear that soaps and extractives do have at least some affect on the water resistance of housewraps.

http://repanet.de/Tyvek_Construction/en_US/assets/downloads/StuccoWrapFactSheet.pdf
It is important to note that in high exposure areas where severe weather and wind driven rains are a significant factor in normal weather patterns, we recommend design of wall systems that incorporate an intervening layer or airspace to maximize drainage. In these systems DuPont™ Tyvek® StuccoWrap® provides enhanced drainage over other two-layer systems. In addition, current literature indicates that inconsistencies in stucco applications and formulations, particularly inclusion of additives (which in some cases may contain surfactants), may negatively impact the water hold-out capabilities of all water-resistive barriers. Therefore, the practice of incorporating unapproved additives into stucco formulations is not advised.
http://www.henry.com/fileadmin/pdf/data/techtalk/Vapor_Perm_Air_Barriers_Tech_Talk.pdf
Also, there appears to be debate regarding the durability of spun bonded polyolefin in contact with the natural surfactants in wood and the adhesives in OSB and plywood.

[Carl A. Brown]

Thanks Larry!

I know they say it is not to come in contact with cement/mortar for the same reasons.

Stucco, brick, and stone mortar joints.


Makes a person wonder whats going to happen to all the houses that have tyvek on them that covers OSB!

Dupont does have deep pockets!!

[David A. Andersen]

Carl, I forgot the source from #6.
Sorry.

It is info I dug up after ITC BS course (not with Larry!).

oops! here it is.

http://www.bobvila.com/wwwboard/messages/230936.html

[Carl A. Brown]

Thanks David!

So this one with housewrap over OSB and stucco does not stand a chance!

http://www.badstucco.com/indexwo/indexwo.html

[Carl A. Brown]

House wrap needs a primary barrier under it if plywood or OSB are used, and a secondary over it??

Kinda runs the price up!


http://www.buildingscienceconsulting...housewraps.pdf

[William J. Decker]

Look;

One has to understand the difference between a "moisture" barrier, an "air" barrier and a "water" barrier.

Again, different areas have different climates and weather conditions and need different solutions.

In out area (midwest, Chicago) the house wrap must be able to "breath". This means that liquid water must be kept out and "moist" air (water vapor from the sheathing) must be allowed to go out.

In our area, most of the hygric buffer drying occurs during the winter, when the temps are in the single digits, and not in the hot (usually humid) summer. This works for multiple layer, structural brick (older houses and newer cinder block with brick or split block veneer) as well.

In Texas, Florida and other Gulf states, the problem is too much moisture. I am told that, in these areas, if you go away for a week during the summer, you must either run your A/C or have de-humidifiers runnng or you will have mold growth inside. Humid, hot climate.

Different areas, different reauirements.

Part of the NACHI Thermal imaging certification, (building science section) class.

Hope this helps;

[jkogel]

Originally Posted by lkage

There was speculation that surfactants (soaps) could make housewraps more water permeable. And we found this to be true. Surfactants, which break down the surface tension of water, making it flow more easily, are present in soaps and oils that can be found on the surface of construction materials and hands of installers. This may be significant since people regularly powerwash their homes, perhaps making them more likely to leak. Also, cedar and other wood sidings contain water soluble extractives that are thought to act as surfactants. Paints and stucco have surfactants as part of their formulation too. So surfactants seemed like an interesting thing to investigate.

I don't think we should condem housewrap in general, just don't rely on it for waterproofing in exposed locations, (or locations where pressure washers are readily available ) .

[David A. Andersen]

Just like Dryvit siding. There is nothing wrong with it if you use it correctly!