tyvek – is it worth it? How is it used?
| Posted in Energy, Heating & Insulation on
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I am a cabinetmaker by trade, but am currently building an extensio0n onto my shop. I notice Tyvek on all the construction site these days, but don’t know how well it works, nor how to use it.
A visit to the Tyvek website was helpful,. but of course they hae an interest in selling the stuff…
my questions:
What does it do? Help with?
Is it used in conjunction with poly VB?
thanks,
J
Replies
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john.. lots of opinions.. lots of discussions..
bottom line consensus seems to be .. stick with 15# felt...
the purpose is the same as stated by Tyvek.. to provide a breatheable rainscreen and wind barrier..
*Mike-I just saw your reply regarding the use of Tyvek. I work at a lumberyard and am currently building a custom home. My uncle is a custome builder and is advising against Tyvek. He says that he has seen large holes develop around nails from siding caused by expansion and contraction of sheathing. My builder is trying to talk me into Tyvek, where can I get more opinions, info, etc...Thanks, Bryan
*go to the panel below and click on "search".. enter the word "tyvek"....then read to your heart's content
*Bryan and John,Be aware that the recommended method of installing siding over tyvek these days is to add a layer of vertical furring strips over top of the tyvek to keep the siding off of it and provide a drainage plane. Cedar siding against tyvek will cause it to break down and become an absorbant rag. After that you'll never be able to keep paint on the siding. I've seen it happen personally as well as read about it in JLC.The furring detail would be a good idea even over #15 felt, since the siding they sell now is so crappy. Anything to keep it dryer is a good idea.Steve
*Steve, you've also read about it in FHB. Issue 137 if memory serves this early.Andy
*Andy,I thought so but wasn't sure. You're on the ball today! BTW, I sure wish we had gotten to meet when I came through the Taunton a couple of years ago.Steve
*Steve, I forget why I wasn't there -- I think I was on a photo shoot, but I regret missing that chance as well. Andy
*"I've seen it happen personally as well as read about it in JLC."What issue was that, Steve? I read, very, very extensively, through every JLC issue, at Andy's suggestion, about this situation and didn't find any information from that magazine to support this. Also, although I found Joe's information in FHB #137 to be very informative, it still seemed to be very biased against manufacturers of these materials. If I missed something, fill me in.Got any pictures?
*Jason,The only thing I could find in my stack of JLC's was a report in the notebook section of the February 2000 issue that detailed the results of some testing by Paul Fissette. That particular item also made reference to an earlier article, again about some testing by Fissette, that I remember reading in JLC as well, that was about the tannin issue. I think that was in the notebook section as well, but was quite some time ago...before I started saving my copies of JLC.I think the story I really had in my mind was the FHB #137 story. That'll teach me to speak from memory. Getting too old and feeble in the brain. I just re-read the FHB story and fail to see any bias against any manufacturer. What I do see is a pretty obvious and extensive example of housewrap that has turned to rags and is soaking wet. Why this happened is purported to be the tannins in the cedar degrading the water repellency of the tyvek. I don't have pictures of the cases that I personally came across, but there was extensive peeling on the windward side on one part of the building and not on another part that had the same windward exposure. The most recent paint job was from the same time on both parts of the building. The part that was failing was un-backprimed cedar. The part that was not failing was backprimed. Not that this proves anything.In another example I peeled open, behind an un-backprimed cedar sided wall that had a flashing problem and was subjected to frequent wetting the tvek exhibited the same rag-like texture and tea-colored staining that you see in the FHB article. Whether this would have happened without the flashing problem is anyone's guess.I think tyvek's most useful function is for temporary siding...the contemporary version of the "tar-paper shack". A couple hundred bucks and you are good to go for a couple of years at minimum. Then when you scrape up the money to do the real siding, you just cut away the tyvek as you go, replacing with asphalt felt as you work your way up the building...Steve
*Those were the articles that I had in mind. Believe me, FHB didn't intend to be biased against the manufacturer. We just reported one example and offered up Joe Lstiburek's (a well-known building scientist)explanation. While that didn't come up roses for the manufacuturer, if pressed, Joe will admit to having Tyvek on his own house. I believe that if you read the JLC article, you'll find that Tyvek fared the best of the plastic housewraps (Still not the equal of #15 felt). My point here is that we need to be careful when using generic references -- Tyvek isn't Typar.Wrapped in felt,Andy
*I went and looked up Paul's research on housewrap and felt, which I believe is at this site:http://www.umass.edu/bmatwt/weather_barriers.html.Here's his quote at the end:"...housewrap or felt? The truth is, there's not million dollar answer. In general, I don't think it matters a whole lot. If you get the flashing details right, and are careful installing the building paper, you will prevent 99% of the moisture problems caused by wind-driven rain and snow. Either product, housewrap or felt, will provide an adequate secondary drainage plane. And either product is permeable enough to allow interior moisture to escape." He says he PREFERS felt because he feels it does a better job at repelling intrusive water, but certainly doesn't say that housewraps are inferior or damaging. Please don't get me wrong, I'm not trying to start an argument or try to say I think one method is better, but I do want to do the right thing with long-term interests in mind for my customers. That being said, it kind of drives me up the wall to see products or methods demonized based on, in many cases (hats off to you, Steve), very little if any information, particularly when people don't have first-hand information on it. Thanks again for posting.
*Jason,Did you read the follow-up study at this link:http://www.umass.edu/bmatwt/housewraps.htmlHe is even more positive about housewraps in that one. Here is the nut of it:"Use a housewrap as a secondary weather barrier under all siding. For my money, I'll choose a housewrap that shows the most promise. Test results narrow my field of potential candidates to Tyvek, Rwrap and 15-pound felt. Felt paper leaked after 30 minutes in the column test, but still makes my list as a strong candidate.I think that felt paper blocks the flow of liquid water under pressure (column) for a respectable length of time. When it leaks under pressure, it seams to leak very slowly. It blocks capillary flow for days. Felt is inexpensive. What is also appealing isthat felt is forgiving. If water gets on the wrong side of a felt-wrapped wall, the felt can absorb the water and over time allow drying to the outside of the structure. Plastic housewraps don't move water this way. Plastic wraps are non absorbent. They rely on vapor diffusion to move water that gets on the wrong side of the wrap. Diffusion is a slow and weak force. The perm rating of felt is much lower (less permeable) than the plastic housewraps when it is dry. But this does not mean that it traps water vapor in the wall cavity. As the relative humidity rises, the perm rating of felt rises too- eventually above that ofTyvek. Felt is dynamic. Having said that I also like Tyvek and Rwrap. They cost more than felt, but these products stand out to me as being very strong products. They roll out as large continuous sheets. They have shown an ability to reduce air exchangeand energy consumption in some studies. And they have demonstrated to me that they can block the flow of liquid water, while allowing diffusion of vapor."Steve
*I thought the purpose of a "house wrap" was to reduce air infiltration not be a moisture barrier. Overlapped felt paper does little for air infiltration.
*Tim,I've always considered its main purpose to be that it keeps bulk water from passing (ie: wind driven rain, etc) while still allowing water vapor to pass out from the inside. Blocking air infiltration is an added bonus.Steve
*tim.. house -wrap may be marketed as an air infiltration barrier.. but it also has to function as a water barrier..what do base this statement on ?...<<>>not my experience.. nor the experience of most of the recent testing in the last two years......i could be wrong....b but hey, whadda i no ?
*Seems to me the prime air barrier is correctly nailed sheathing...Andy
*what about using tyvek housewrap underneath felt, would this work. relative to our normal method of building, stick-framing is cheap here in ireland. that is why i'm doing it. so if there is no problem with this method, i'll use both. IS THERE ANY PROBLEMS WITH THIS METHOD?
*eddie....Pick one to use...Using both could cause more moisture problems than it stops.near the eddie..in the stream,aj
*why so aj?
*Eddie....when one comes to you with the knowledge...it is sometimes wise to go forth with faith...leave your backwater swirl behind eddie...time to enter...the stream,.know that one is better than two...that proper torque is better than overtorque...or no torque...Moderation...seek the middle eddie as the eddie in you does so naturally...now go forth.
*Mike, I based that statement on nothing scientific, such as testing or the like, seems as if its wrong. Seems to me, that there would be no seal, course to couse, for the felt paper to keep out air.Properly nailed sheathing, over the whole exterior of a house? Andy, that sounds great, but the 2 houses that have owned didn't have it. Wind bracing on the corners only of the 1971 house. 1x4 nailers on 4' centers for the vertical sididng and armstrong stuck between. The 1903 house had 1x4's with 1/2" spaces for "sheathing", under stucco. Obviously, niether of these meet current standards.
*I'm not sure how to help an old house like you describe, except to dense-pack the bugger with cellulose. In a new house though, properly-nailed sheathing doesn't seem like much to ask for. In fact, I've always demanded it. Andy
*Don't know where you live, but in N. Michigan everyone I know has stopped using tyvek especially around the bottom layer of the house. They are all going back to felt. Why? The builder I fill in for on occasion told me they recently pulled back the tyvek and found the entire sill rotten on 5yr old home. Why? tyvek is damn near perfect barrier, houses produce moisture-breathing, plants, basements, heaters, washers. Where does the water go if you wrap your house in plastic. nowhere it stays in the walls and rots the framing. I'm no expert but tar is meant to keep a volume of water from the sheeting. Not to create a perfect seal. Especially in cold climates I understand the vapor barrier needs to be on the warm side not the cold side. However, ask 20 builders and you're probably going to get 20 different answers. I know I have. Bottom line- new products can be great, but they're new I'm waitng ten years when people start remodeling homes wrapped in tyvek to see what the walls look like. We tore the back off our 100 year old inn and found tar paper in near perfect condition.
Tom,
You have your moisture dynamics confused. Yes, Tyvek is an outstanding barrier to air and bulk water. It is however, a highly permeable product, it breathes much the same way as Gore Tex. The situation you decribe could not be caused by moisture build up due to moisture vapor escaping through the walls. The quantity of water and degree and location of the damage would indicate a leak. The reason most damage is visible on the first floor is water enters at a higher point on the wall. Windows and door are notoriously improperly flashed if at all. Rot is caused by wood being saturated over a long period of time. Windows can act as a funnel to direct water to a localized point in the wall. Care needs to betaken when the window and flashing are installed to direct that water away from the structure and towards daylight.
With regards to you 100 year old inn. Old structures are very leaky to air. This means that a sufficient amount of air circulated throught the wall cavity in order for the drying rate of the structure to be greater than the wetting rate. The cavities were void of insulation which allowed free flow of air throughout the exterior walls. In addition, balloon framing techniques(long studs from sill to top plate) were common. we don't utilize this now due to code for fire stopping.
buck.. tell us some more about yourself... you seem to be advocating very strongly for tyvek...what else would you like to share ?Mike Smith Rhode Island : Design / Build / Repair / Restore