Is there a time limit to how long building wraps (ie: Tyvak or Typar) can be left up and exposed to the elements before it needs to be removed and replaced ? We have a job that the Tyvak was left exposed over the winter, do we need to remove this and reinstall new Tyvak?
Yes, each synthetic house wrap is given an exposure rating. The sun's UV rays break it down. As for a chart there is one, However i cant recall where. Im sure you can find the makers website and it will tell you but i recall a chart either here (JLC) or FHB. Magazine or online...
Not only does the UV rays break down wraps but also wind eats the stuff like a bush hog, Dirt and grime will gather on the wrap and reduce its ability to deal with water in its intended way.
Your wrap may fall into the correct timeframe on NOT to put up new wrap, however if your wrap has come loose, shreded or frayed then its not effective as a barrier.
There was an article in Fine Homebuilding addressing this exact subject. I happened to read in Tauntun Press's book on energy efficient building techniques. Basicly the book is a collection of past FH articles. The upshot is there is a chart in this article that details the exposure time for various house wraps. As I recall, Typar had the the longest esposure rating. Sorry I can't tell you the isuue this appeared in but I hope it will get further down the road.
The article that Loy refers to is Sizing Up Housewraps by Bruce Greenlaw and was published in Taunton's Builder's Library Issue of Energy Efficient Building. It comes from the October '94 issue of FHB (Issue 91), pages 42-47. If there haven't been any major stides in formulation of these products since '94, the chart should be very useful to anyone wanting to know how much time they can safely leave these products exposed. (Personally, I'd take the time limit they state and reduce by 40% just to stay safe.)
Assuming that it is Tyvek you have and not another brand, you can only leave it exposed for 4 months (120 days) before UV exposure will cause serious performance degradation.
Here's how the chart breaks them out:
Celotex TuffWrap........3 months
Du Pont Tyvek
Simplex R-wrap..........4 months
Also do a search of the archives here for house wraps. There's some pretty good stuff here. Paul Fisette wrote a pretty good article in '99 about how extractives will affect wraps and Martin blessed us with one either last year or the year before.