*
Now that I’ve completely gutted my 100-year-old Settle home what better time to insulate and add a vapor barrier, right? My question is weather a vapor barrier will create more problems that it may solve.
Here’s why: The house is two stories with the second floor rooms entirely within the gable. I’m worried about a vapor barrier because 1.)it may be impossible to really make it airtight, thus creating avenues of high-water content, rot-producing air leaks in the winter and 2.) it will funnel all the water vapor up into the attic where — as of yet — there are no attic vents.
In Settle, where a lengthy freeze is a rare thing, why bother? Why not just let it disperse evenly out the walls?
Replies
*
Ya you do that.
After all, what do we know.
Gabe
*Yo, Dumb as it may sound, it was a serious question. I don't think vapor barriers are even required here. The house survived for 100 years without one.
*Only if you restore it back to the 19th century and live the same lifestyle.If you gut and modernize then you do it right.A vapour barrier that isn't install properly is not a vapour barrier, it is a piece of plastic caught between your components. If you take the time to do it right and seal all the penetrations, it will save you money and make your house easier to heat, cool and maintain.choice is yours of course, but if it were mine....Gabe
*This is an excellent question, and one that deserves more attention here in Western Washington. As a third Generation contractor in Tacoma, WA. we have found more problems from vapor barriers than benefits in most cases. Retrofit vapor barriers tend to seal in moisture here. With a relative humidity at 100% for much of the year,the wood structure is going to raise it's moisture content. When this wood cannot expel this moisture, problems arise. I know this seems to fly in the face of current trends, but time and experience has proven it out. Probably in many parts of the country, the retro vapor barrier you describe may be usefull, but here, we have seen numerous problems. As an example, you may recall the " Super Good Cents" homes from a few years past. The walls and ceilings were wrapped in a tight poly vapor barrier. We are making a pretty good living off replacing the dry rotted wood members in those homes, though only fifteen or twenty years old. Wood needs to breathe. It is an unmutable fact of life. We as builders try to change the carachteristict of the wood to better suit our needs. But asking wood not to raise in moisture content, at least here in the soggy N.W., is like asking wood not to expand and contract. It is going to happen, and the best thing we can do is to controll it, and accommodate it. Now for your home, the best thing you can do is provide plenty of good ventilation in the crawl space, and plenty of good ventilation in the attic. The average home in Western Wa. passes three hundred gallons og water through it every year. This is an industry accecpted fact, even in new homes with extraordinary vapor barriers. In my humble opinion, we, as builders and remodelers, need to stop trying to change the laws of nature, and find better ways of dealing with it on it's own terms. Good Luck
*Concur 100% with Kevin. Venting is everything here. Had to retrofit a roof over cathedral ceiling (Renton, WA) with continuous ridge vent to keep the wood dry, the ceiling had adhesive sealed poly barrier. Reroofed a rental house (Kent, WA) that had eave vents only every other 2ft. truss span and had to replace sheathing (built 1970), added additional eave and roof vents in addition to existing 2 sq ft. (>code)end gables vents.
*Kevin,Before you condemn VB you should know 2 things.1. How to install it properly, so that it doesn't fail.2. Appreciate the fact that you've only worked on houses that didn't have it installed properly.Time for the next generation to join the 21st century.Gabe
*I believe Gabe is correct and I believe Kevin is correct, depending what your goals are for the home and what ability you may have to reach those goals.If you want the home to last another 100 years and you do not care what it costs to heat and cool, or how comfortable it is, then do not insulate or tighten the envelope in any way. If you want a comfortable home that is economucal to operate then tighten and insulate, if it is possible. It may not be possible due to the condition of the home or your resources. If you do tighten and insulate, you must do a near perfect job of air sealing. Stoping all air movement through the envelope will prevent 99% of moisture movement through the envelope. The mechanical systems must be designed to condition the air 100% of the time and create the correct pressure differentials for your situation. A good source for information on home tightening and controlling moisture flow is the "Builders Field Guide" by Joe Lstiburek.
*Hi Jim, I am a remodel contractor in Seattle and I've seen people do it different ways. Kraft face insulation gives a vapor barrier. Some use the 4 or 6 mil plastic over unfaced batts. One of the Seattle DCLU inspectors told us a couple of years ago to just roll on two coats of PVA drywall primer and that does the job. That is what I now do and I put the insulation in or have someone blow in cellulose or fiberglass and then I do the two coats. Plastic seems too extreme, let 'em breath a bit I say.Bob
*Jim, I think you are wise to consider the breathability of your construction. There have been many studies in British Columbia about why so many of their wood buildings have rotted over the past ten years, and many there have concluded that the use of polyethylene vapor barriers had a lot to do with the damage. Not the primary cause of the rotting problem ("it's the leaks, stupid!") but, yes, a contributing factor. The walls could not dry out because the sealed plastic did not allow drying to the interior. You might be interested to know the Seattle building department is researching the vapor barrier issue in depth with Oak Ridge National Laboratory. You might contact them.
*Thanks Robert and Mike and all the others who weighed in. I'm settling on kraft-faced batts and vapor barrier rated paint. It's easy, seems thourough if applied right and the city tells me that will work. Thanks again for the good information.
*
Now that I've completely gutted my 100-year-old Settle home what better time to insulate and add a vapor barrier, right? My question is weather a vapor barrier will create more problems that it may solve.
Here's why: The house is two stories with the second floor rooms entirely within the gable. I'm worried about a vapor barrier because 1.)it may be impossible to really make it airtight, thus creating avenues of high-water content, rot-producing air leaks in the winter and 2.) it will funnel all the water vapor up into the attic where -- as of yet -- there are no attic vents.
In Settle, where a lengthy freeze is a rare thing, why bother? Why not just let it disperse evenly out the walls?