House Wrap

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

Does House Wrap stop or minimize air infiltration?

Your comments please


It lets air out without letting water in, AFAIK.

Here is a link to DuPont/Tyvek…

And Owens Corning/PinkWrap data sheet…

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

Unless it is an air barrier, No.

What product are you talking about?

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.

The Tyvek or similar is what I was referring to


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.


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”.](
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.](
[FONT=Univers 45 Light]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.[/FONT]](
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.

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!!

Carl, I forgot the source from #6.

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

oops! here it is.

Thanks David!

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

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

Kinda runs the price up!


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;

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 ) :p.

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

Here are necessary readings to fully understand this system as housewraps are intended to perform more than one function:

There are more but I haven’t the time to find them now.

from the article that CBrown referred us to:

You would have to be insane to recommend a vapor permeable assembly behind a
rain wetted reservoir cladding system experiencing these kinds of drivers. Now, in fairness
to a 50 perm housewrap, it works well when it’s installed over a 1 to 2 perm OSB
sheathing behind a brick veneer. It’s another story when the 50 perm housewrap is
installed over a 15 perm fiberboard or a 25 perm gypsum sheathing. With the OSB, the
water vapor is stopped at the outside surface of the OSB and then migrates back outwards
through the housewrap into the airspace behind the brick veneer when the gradients
reverse. With the fiberboard and gypsum sheathing the water vapor blows right through
the assembly into the wall cavity where it causes mischief.
Now let’s get a little more complicated. The #30 felt doesn’t cover itself with glory
in the same application described above. It changes its permeablity as its moisture content
goes up. It is a hygroscopic material. Depending on how well vented the brick veneer
cavity is (actually, the correct phrase is depending on how poorly vented the brick veneer
cavity is), the #30 felt increases in permeablity as it picks up moisture to match the
permeability of the housewrap. So installing #30 felt over fiberboard or gypsum sheathing
is not necessarily a big improvement over installing housewrap. However, installing #30
felt over OSB works well (and so does the housewrap).

Re housewraps used under conventional stucco, and [FONT=Univers 45 Light]StuccoWrap® in particular:

'In spite of the name, the only
product StuccoWrap doesn’t seem to
work with is stucco. When the stucco
bonds to the StuccoWrap, drainage is
lost along with water repellency.
Stucco applied to StuccoWrap produced
the second worst performance
of the systems in our test (the worst
was stucco applied directly to a nonwrinkled
plastic housewrap).

But StuccoWrap was also part of the
best-performing system we tested.
When we added a cheap felt paper
over the StuccoWrap and then applied
the stucco, the system worked perfectly.
The cheap paper was a bond
break, the StuccoWrap remained free,
and then we saw tremendous drainage
in the grooves…"

[/FONT] - Joseph Lstiburek

First met Joe Lstiburek at a major building conference in 1985 in Ottawa. He was with a mentor, Gus Handegord of the Division of Building Research of Canada’s National Research Council. Gus was an early giant in building science…in Sept, 1960, he authored Canadian Building Digest #9 ( ) on vapour barriers and said in his closing line:
“The conditions to which the vapour barrier is exposed after installation are a factor, but the circumstances during application are usually of most importance. The most important general principle to be followed in both design and installation is to reduce to a minimum the number of openings in the barrier. Where such openings are necessary, special care should be taken to seal the barrier so as to approach complete continuity.”
So you see where Joe gets it from!!! Mentioning sealing the vapour barrier (to complete it as an air barrier) 48 years ago. Much of this building science theory is not new but just hauled off shelves…materials and practices are evolving fairly quickly so you have to keep reading constantly or be behind.

Have had the chance to hear Joe speak about 7-8 times as my old dept. used to bring him to Nova Scotia about every 2 years to speak at a very technical housing and energy conference (ENERHOUSE) and also to speak to carpentry and architectural students. Had the occasion to spend 3+ hours driving him between distant speaking engagements. Quite a mind!! A funny speaker…brash…entertaining…different…a maverick …always showing the future…and usually never wrong!!! If you ever have the chance to hear him, take it!!!