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vapor barrier
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Author:  Jason Hall [ Fri Mar 19, 2010 7:20 pm ]
Post subject:  vapor barrier

Should I put plastic behind all the walls and ceiling of my RH controlled room as well as the floor? I know vapor protecting the concrete floor is important.. but is doing it to the whole room subject to diminishing returns?

Author:  gozierdt [ Fri Mar 19, 2010 7:43 pm ]
Post subject:  Re: vapor barrier

I believe it will help you control the RH more easily. What are the walls- are they raw studs
now, or already covered with wallboard. And are any of the walls on the outside of the building,
if so, you'll want to insulate them to help with temp control.

Author:  Jason Hall [ Fri Mar 19, 2010 9:09 pm ]
Post subject:  Re: vapor barrier

It's a stud wall built inside my garage, actually halves the total size (about 320sq. ft.) of the garage. So 3 walls are to the outside, and the one I build is inside. On the outside of the stud wall I built, is 7/16 osb, I'm not sure if I should have drywall on the inside, or some kind of wood.. any opinions on that folks? One of the garage walls already had insulation in it.. It was like they had some insulation leftover from when they put the upper level of my house on (before I bought the place). I got the same stuff they used, and insulated the rest of the walls including the one I put up. I'm just trying to decide if "encasing" the entire room in plastic will gain me much as far as temp and RH control. It makes sense that it would... but will it make enough of a difference to justify buying more and doing the extra work.

Author:  JohnAbercrombie [ Fri Mar 19, 2010 10:51 pm ]
Post subject:  Re: vapor barrier

Jason-
Any time there is a temperature difference between the two sides of a wall, you should put a vapor barrier on the warm side of the wall. The purpose is to prevent warm moist air from cooling inside the wall cavity and causing condensation, which will lead to mold growth and rot.
If you put a wood floor on sleepers over concrete, the vapor barrier should be just under the floor, over the sleepers (and hopefully insulation) and concrete.
And if you are going to leave the (leaky) garage door in place, you definitely want to have vapor barrier on the warm side of the dividing wall.
The vapor barrier also keeps the inside warmer since it prevents warm air from leaking through the walls.
The vent fan that Hesh recommends is a good idea.

Cheers
John

Author:  Chuck [ Sat Mar 20, 2010 9:29 am ]
Post subject:  Re: vapor barrier

I decided to insulate the inside of my garage as I was putting a gas heater in the garage so I could go out and work in the winter. I used a vapor barrier on the inside of all the walls and ceiling. I was not really sure if I needed to do this or not but having lived in some very cold weather I thought it was a good idea to put the vapor barrier in. I have been glad that I did this.
Chuck

Author:  Jason Hall [ Sat Mar 20, 2010 9:44 am ]
Post subject:  Re: vapor barrier

Thanks guys.. that's decided me. What kind of insulation should be used on the floor? If the plastic is supposed to be just under the floor, then the wood strips and insulation will be subject to the effects of moisture. Not sure how to go about that.

Author:  JohnAbercrombie [ Sat Mar 20, 2010 11:25 am ]
Post subject:  Re: vapor barrier

Jason-
I think I was incorrect in my advice about the floor treatment.
Some quick research showed that you do in fact need to put the plastic right on the concrete, and that insulating the floor is probably not very necessary.
(Having a non-concrete shop floor has a lot of benefits - one will be obvious the first time you drop a chisel.)
Cheers
John

Author:  Howard Klepper [ Sat Mar 20, 2010 1:20 pm ]
Post subject:  Re: vapor barrier

Read the articles listed on the right side of this page. Very helpful.

http://www.askthebuilder.com/VaporBarrier.shtml

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