Isynene in rafter bays – vapor or not
Woodside
| Posted in Energy, Heating & Insulation on
I’ve read a few messages regarding isynene. I plan to install it in rafter bays and sheetrock to make a cathedrial ceiling for a 3rd floor office. The 3rd floor joists are already strong enough, and the heating to the 3rd floor is roughed in. The question is: Do I need a vapor barrier under the sheetrock if the icynene is sprayed agains the roof sheithing?
Thanks
Joe
Replies
will all of the wood be covered up?
if any wood is exposed that will be where you'll find the start of rot. . vapor doesn't care where it goes, just so long as it can go someplace.. if it's path is thriought the joists, that is where it will go.. get wood damp enough, long enough and it will rot..
sure it's better than fiberglas and celluliose but you need to anderstand it's properties.. used properly with no vapor path and it's the best ting since sliced bread. leave a vapor path .....
There are some areas that will not be covered. For example, behind the knee walls. I get you're point. Know the system and act accordingly.
Thank you!
NO! No VB required, Frenchy is wrong but won't admit it.
Frenchy has no clue what is causing his own moisture problem, don't listen to him.
If you need a forklift, he's your guy.
Joe H
Thanks for the reply. Just so I'm clear. I have a 3rd floor. Rafter bays sprayed with Icynene. Gable walls with fiberglass. both walls and rafter bays sheetrocked. No barrier required?
Thanks again.
Joe
Yup, no VB. See this thread also, same subject again, twice.
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=38437.1&maxT=6
Joe H
I would go ahead and install a vapor barrier. You'll need one on the areas that have fiberglass insulation. I worked with icynene for the first time this past summer. The installer was adamant that we didn't need a vapor barrier. I looked closely at the specs for icynene: "icynene is water vapor permeable". The specs also say that if the climate you live in is as cold as or colder than Madison, WI. then you need a vapor barrier. How much does a roll of plastic cost anyway? If you dont' put in the vapor barrier and end up with moisture problems, the cost to repair could be very high indeed. If you put up a few rolls of plastic it's cheap insurance.
After you have sprayed the Icynene into the cavities, spraypaint the entire area with a good latex paint before you install the drywall and you will have no problems with moisture damage.
Gabe