Building Wrap

[peter nap]

I was talking to a builder yesterday who is using black plastic as a building wrap. Not just around windows,doors or under the splash guard, but the entire exterior wall. I was always under the impression that the wrap, Tyvek or felt or whatever, needed to breath and if it didn't. condensation and related problems occured.

Any opinions?

[glenn kangiser]

Yes -- of course--

The black plastic will probably have the the same problems as the Tyvek.  In the case of non-condensing vapor the Tyvek may let it out, but if the vapor condenses or either of them get a hole or improper flashing, they will both cause mold and rot problems.  Water not pass through Tyvek or plastic to get out.  Holes and problems are nearly inevitable.  Many houses and apartments in the PNW have had major problems with Tyvek or house wraps and last time I was there I heard of an apartment complex that had to be torn down because of it.

Felt will wrinkle and drain or if water gets behind it for long enough it will wick then dry out and become it's good old self again.  No tear down problems with felt if the builder does a half decent job.  It is pretty forgiving.  

Sometimes the old ways are the best ways.  There is a reason they stuck with felt for so many years.  It works.   8-)

Just because corporate America comes out with a new product, pays off enough of the building bureaucracy to get their product approved, and supports it with a multi-million dollar advertising campaign, that doesn't mean it is the best.  

It just means that there are massive amounts of mioney to be taken from the unsuspecting gullible public. :-/

[peter nap]

Thanks Glenn. I figured pretty much the same.

I never used Tyvek when I was building. I worked on a few crews that used it but they would frame and wrap the house and let it sit for weeks at a time until the siding people came. The news came out about that time that it was not UV stabilized and 24 hours was all it could stand.

Lots of unhappy homeowners around then.

I'd rather use felt anyway. It's about 60.00 a roll cheaper.

[Homegrown Tomatoes]

My sister and her husband bought a brand new house which, of course, stood wrapped in Tyvek for a week or two while being built.  Within a month of moving in, they were taking kids to the doctor constantly with sinus/cold symptoms, and then visible mold started forming around the windows and on the walls.  My sister is completely germ-phobic anyway, but nothing she could do would stop the mold.  She had the builders come back 3-4 times and try to fix the problem, which was never fixed.  Finally, they gave up getting it fixed and let the bank reposses it (they refused to sell it with the problem, and the builder claimed they'd "fixed" the problem.)  Both of their kids were chronically sick while they lived in the house.  It was a $128K house (not cheap in that neck of the woods at all!)  Sometimes the newest stuff isn't at all the best... and it's another great reason to build your own... at least you know what has gone into it and you have done your best to avoid poisoning yourself.

[MountainDon]

From the reading I've done I believe most of the problems attributed to Tyvek, Typar, and the like could be traced back to other faults that allowed water to get behind the housewarap. Things like improper flashing around windows and doors and plumbing, electrical, and other wall penetrations that allow water to get behind the house wrap. The nature of the house wraps is such that only water vapor can pass through it. Water stays trapped. Building paper will absorb the water and allow the water to dry to the outside air.

So properly installed, meaning the whole wall covering process, the house wraps should be a good choice. However it is interesting to note that the Director of the University of Massachusetts Building Materials and Wood Technology Center states he would choose felt paper if he were building a new home.

Article at:  http://www.umass.edu/bmatwt/publications/articles/housewraps_feltpaper_weather_penetration_barriers.html

Long article, but interesting. Here's an interesting excerpt...

"As it happens, I have felt paper on my own home, and if I could choose between felt and housewrap and do it over again, I'd still choose felt. That's because I believe that under certain circumstances, felt outperforms housewrap. For example, an ice dam or roof leak may allow liquid water to get behind the felt or housewrap. It's also possible for the sun's heat to drive water vapor through the housewrap from the outside, where it can condense on the sheathing. In either of these cases, you now have liquid water on the wrong side of the wrap. Under these conditions, the liquid water would be trapped by the housewrap, which is permeable only to water vapor. Felt, on the other hand, will absorb the water, and more quickly dry to the outside."

Another interesting article...

http://www.buildingscienceconsulting.com/resources/walls/drainage_planes.htm

I read this one with interest as it explained why my stuccoed home has 2 complete layers of felt, one over the other. I found this out when I cut a new doorway through an exterior wall years ago.

For those who don't want to read the articles and are using wood siding materials, the authors highly favor installing the final wood product over strapping/furring strips over the weather barrier to provide a virtually foolproof drainage plane behind the wood.

"Physics shows that free drainage occurs whenever an airspace is greater than 3/8-inch. The surface tension of water will not allow water to span a gap greater than 3/8-inch. On the suction side, capillary suction will not occur with gaps greater than 1/8-inch."

One final note of possible interest. I've read somewhere and forgotten where, that building paper/felt has changed and is no longer as heavy as it used to be. It used to be rated by how much it weighed per 100 sq. ft. as in being referred to 30#, 15# etc. (the # symbol behind the numerals to signify pounds) Then back in the Carter days and the oil embargo, the product was reformulated with less asphalt. The labeling system was changing to todays #30, #15, etc. (the # symbol before the numerals to signify number not pounds. #30 is apparently closer to the old 15#. It's still referred to as 30 pound, 15 pound, but that is technically incorrect. Note that todays product labels clearly have the # symbol before the number.

As with many improvements the law of unintended consequences can and does rear its ugly head.

BTW, I'm planning on using #30 felt.  

[peter nap]

As usual Don and Glenn, you have helped work out am oddball problem. BTW Don, how do you keep all that straight in your head?

What I've been working on is unusual (so what else is new. This building will be tight and as John pointed out, it has to be to prevent condensation on  the roof. I was looking for a way to wrap on the inside of the girds to allow an airgap between the celotex and the board and baton siding. This necessitates putting the wrap on the inside of the girds and was the reason for my conversation with the builder the other day.

After reading Don's article, The one and a half inch gap between the celotex /tarpaper  and the board and baton siding is way more than enough. That was a bonus that I hadn't thought of.

[MountainDon]

BTW Don, how do you keep all that straight in your head?

In My Head???    That's a very cluttered place Peter. And not nearly as organized as I would like. It's search engine works, but runs into corrupt data more and more.  

I use other computers; my laptop and the backup file server. I have loads of bookmarks and when I find something I really like for some reason I "print" it to a PDF file, with the original URL copied as well, and file that away in folders with way too many sub folders.  :-/ At least I try to do that; sometimes I fail and those are usually the things that disappear from the web, or at least get lost to me.   :'(  Sometimes I do have trouble sorting through and finding what I want. Too much stuff to look through.  :'( Sometimes it's in a spot that seemed logical at the time of filing, but doesn't seem to "fit" later.  

[glenn kangiser]

Thanks for that experience, Homegrown.   Nice to have back up by near hands on knowledge.  Not so nice for the victims.

Don and Peter, the think that bothers me about the Tyvek style wraps is that it is almost rocket science to do them properly and even the things go wrong and they just don't work satisfactorily.  Things commonly go wrong and it is always someones fault for not doing this that or the other thing right.  

With felt you generally don't have the problem even if things weren't done perfectly -- it works as it has for over 150 years.

 

The Barrett Corp. claimed to have invented tarpaper in 1854.

I noticed the difference in 30 lb felt and #30 -- I didn't catch on to what it really was though.

[MountainDon]

Ya' gotta watch your flashing too!

[FrankInWI]

  Ok, we took the plunge....son and I returned from a week of making sticks go vertical off our slab in the country.  We learned a lot, and wish I could go back and "remodel" a bit more than we did already.  
It seems very possible we won't get it done before winter sets in.  We mostly only will have weekends now.  I may have to put timporary cover on the project.... with plywood over gaps where dormers will go, etc.  
So not only as a building wrap, but as a roof cover (temp) this is an important topic to me.  I figured on the felt on the sides, and on the top, but now.... I have to wonder about this: Synthetic Shingle Underlayment"  

"ROOF WRAPS

Synthetic roof underlayments mimic the attributes of housewraps, serving as a secondary weather barrier with better resistance to tearing, moisture, and ultraviolet rays than traditional roofing felt.

Synthetic underlayments typically weigh less than felt building paper, can be manufactured with an anti-slip surface, and can withstand exposure to the elements for six months.

After hurricanes ravaged the South in 2005, many homes required quick roof repair and "drying in" to minimize further damage due to water intrusion. With limited resources, contractors triaged homes, repairing the critical components and installing synthetic underlayments as temporary roofing. The underlayments performed better than the blue tarps handed out by the Federal Emergency Management Agency. In addition, the underlayment didn't require replacement when a roofing crew eventually arrived to install shingles.

Two manufacturers, Elk and Grace, offer a Class A or B fire-rated synthetic underlayment.
"
 What do you folks think / know?  

[MountainDon]

What do you folks think / know?  

Hmmm.  I've walked on the Interwrap UDL Titanium roof underlay.  http://interwrap.com/dev/  
It's under my homes metal roofing. It's also Class A fire rated. It's a gray textured material, easy on the eyes and non slippery to walk on. It didn't feel too bad when it started to rain. The wind blew. It got colder. Then it snowed, but by then everybody had gone home. Job completed about a week later. There are 2 thicknesses available; I have the UDL-30 (25 mil). I tried to tear it. It was very difficult to tear.

I've seen felt sit thru a winter on a roof and walls and it seemed okay. Mind you it wasn't mine and I didn't inspect it up close.

Tarps always seem to billow and blow in the wind. Mainly I think because there's nothing much holding it down as per what I have seen. Once they start flapping, they quickly fail.

[Okie_Bob]

This topic seems to rear it's ugly head every couple of months, weeks, days?! It seems that it comes down
to personal choice as much as anything else. Tarpaper or Tyvek or ? I've had the same arguments with myself
and to show how debatable it is, I ended up with tarpaper on my garage/apartment and tyvek on my house. Then
of course, there is the new hardwood flooring I just recently put in and used #15# felt under it. (now is it #15 or 15 pound?)
So far, I can't tell any difference in the garage or the house. And I must admit, I recall that the tarpaper was exposed to a lot more
UV than was the Tyvek or so it seems. One thing I do know, on one south wall in the garage, I can actually see the tarpaper..no insulation, no sheetrock and only cut-in bracing. I have Hardi Board on the outside. I have looked at that wall every time it rains or the weather changes either direction and can see no evidence of any moisture, none, nada, zilch.
So it seems to me that either could do the job and I'm not sure which is best. Could be it's a function of where you are building and the other materials you plan to use?
Okie Bob

[glenn kangiser]

My problem with Tyvek types is that they have no forgiveness.  It's perfect or nothing - not even the pros can always do it right.

So since felt - tarpaper is always at least forgiving, I choose it.  The pro's like Tyvek because they can wrap an entire house in a very short time.  Not because it is good.  Maximize the bottom line.  Time is money.  Finish that crackerbox then get onto the next one.  No time to play with 3' wide rolls of felt - even if it is better.  House those animals.  Finish those cages.  In the housing complex rush, there is not time to lose on the better method.  It's all about the minimum accepted by code and make the maximum of the almighty buck.  I know -- I plumbed 4 houses for some of the a-holes.

[skiwest]

How about the Dow product STYROFOAM WEATHERMATE Plus  as a wrap, thats what my builders wants to use.  wants to use on roof under metal also.

[John Raabe]

STYROFOAM WEATHERMATE Plus is similar to Tyvek (polyolefin) with the advantage that it is translucent and easier to staple down.

http://www.dow.com/styrofoam/na/res-us/products/weathermate_plus_housewrap.htm

I have not had any experience with this product.

[peter nap]

Anyone know the cost?

[MountainDon]

I can see that the translucency of the Dow product as an advantage if you're trying to secure to a particular spot.

[tjm73]

Went to a CSI sponsored meet & greet/product fair the other week. There was a product their that looked very promising. Unfortunately I don't have the material with me and can't remember the name.  But basically it was a fabric one way vapor barrier for housing wrapping.

The demo was an acrylic tube with about 20 ounces of water above the material and an air space under the barrier. A hand pump like a blood pressure bag was attached to the bottom of the airspace. Couple pumps pfhte hand pump and air bubbles rose through the barrier and water. Impressive. Zero water passed through the barrier.

They had a cartoon frog as the product spokes animal.

[MountainDon]

The flashy displays are cool to see, I must admit that.

When you compare all the new waterproof but water vapor permeable wraps though they are pretty much the same and have the one same fault. When (not if, when) you get water on the wrong side of it you could have a serious problem in the works. And you likely won't know about it until much later when the problem has become more serious.

[tjm73]

I remembered the name. Vapro-Shield. http://www.vaproshield.com/