Does my garage need a vapor barrier? Please help

[Danhnrtz23]

Hello all, thanks for taking the time to read my question. I have been getting mixed signals all over and I need a definitive answer so I can put my last pieces of drywall up and get my garage finished before winter. I am not expert and after I got most of my drywall up and blew my fiberglass insulation, my wife's mother asks "did you put down the plastic vapor barrier?" Thanks for asking after the fact. Frantically I panicked and asked numerous people their opinions and most were different. Now I have alotttt of venting in the attic space of my garage, I put the baffles in, but I also have venting all the way up to the top of the roof and all the way across, it's vented throughout . I just have OCD and don't want to have mold form in a few years from now... I spent over 100-150 hours on my 900 sq. ft. Garage over the summer and am nearing the finish line. I have already blown the insulation and put most of the ceiling up except one piece cause I still have to install the heater. I won't be cooling the garage in the summer only heating in the winter.

My question is, do I need a vapor barrier? I live in the northern Wisconsin climate, and have been told I could use expensive mold proof primer as a kind of a vapor barrier , or is it absolutely necessary to get plastic up there and make a proper vapor barrier? I don't plan on running cars in garage either, should I put a vent up? Thoughts? Thanks for your time I am panicking here...

Dan

 

[Marctrees]

Located in N WS climate, you should definitely have put up poly directly behind your sheetrock.

Ceilings and walls.

At this point, all you can do is find somekinda Low Perm paint.

And very important to tape/ mud all joints as in house, to reduce/ eliminate air to move
into your walls/ ceiling.

And remember - Mother knows best.

https://www.google.com/webhp?source...&espv=2&ie=UTF-8#q=vapor barrier cold climate



https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=low perm paint

 

[Danhnrtz23]

I can still "technically" get a barrier in the ceiling area, I would just have to move the blown insulation as I put it up . It would absolutely **** to do it, more than anything , but if it is especially reccomended I'll do it. As for the walls I would have to take them down to do it. It ***** considering the hours and hours I put into the garage. Is there anything else I could do to further prevent any issues from arising? I am almost considering just giving up and just making it look nice but just not heating it to avoid any issues arising... Now I just don't know what to do

Dan

 

[sands35]

my wife's mother asks

Clue #1.

No, you don't need a vapor barrier. The wall needs to dry to the inside. The poly would prevent that.

Climate Zone 7?

http://www.greenbuildingadvisor.com/blogs/dept/musings/do-i-need-vapor-retarder

and

http://www.greenbuildingadvisor.com/blogs/dept/musings/vapor-retarders-and-vapor-barriers

Rose continued, “They produced prescriptive recommendations that later became code requirements, and these prescriptions embodied the incomplete and biased nature of their analysis. They supported their argument with a flawed and misleading analogy. They and their followers left a legacy of consumer fear of ill-defined moisture effects in buildings and of designers assigning excessive importance to prescriptive measures.”

Kraft faced fiberglass and latex paint is all that is needed. Seal up any air leaks and be done with it. Just caulk around any inside and outside wall penetrations. More important to prevent air leaks than anything else.

 

[Junkman]

I vote for the vapor barrier, and if you want to save some time, just put the plastic over the sheetrock, and screw another layer of 3/8" sheet rock over the plastic. It will be a lot faster, and a lot easier now, then tearing the walls apart. I doubt that you will be able to salvage the original sheet rock, and the insulation will be all over the floor, and you will have to deal with that.

 

[Marctrees]

"The wall needs to dry to the inside."

If he was like in FL, or any "hot humid"that would be correct, OP is in opposite kinda climate.

Totally false, study on it, where he is located.

Newest research makes it fuzzzy when in mixed climate.

Many places, vapor barrier is not as desired as once thought.

But not where OP is.

He is in N WS and some are recommending NO vapor barrier?

But then, recommending to "seal any leaks" ?

Those two add up to make a lower perm overall barrier.

Conflicting info.

If you say he doesnt need a barrier, but needs to seal leaks (which he does at least)
then clarify why he should not ALSO have somekinda "vapor barrier"??

Yes, it has proven to be true that holes, gaps, and similar are the worst contributors to vapor passages.

You DO NOT have to pull down rock to install poly.

Junkman above post had a better alternative, or the total taping/mud and coating.

O MY GOD, what a nightmare mess that would be.

BUT study all the info above, and dig for most current scientific info, and make your own decision, never forgetting WHERE you are Geo located makes ALL the difference in vapor barrier location in the wall, or necessity of it.

And of course, it is all moot if you are not heating the area, but your children or Wife's future husband may want to.

Open to arguments, Marc

 

[James-W]

What is the difference between insulation in a house and insulation in a garage? Why does a house need a vapor barrier but a garage doesn't? Not to have a vapor barrier in a heated garage makes no sense at all to me.

 

[Marctrees]

James-W is totally correct, but again, it ALL TOTALLY depends on the climate area.

Google is your friend. Marc

 

[Radix2]

What do you have in the walls already ? The normal kraft faced insulation is sufficient. For the ceilings go with a normal vapor retarding paint and seal any leaks around fixtures.

No one is installing any plastic films under drywall around here...

 

[Dick in Wisconsin]

I'm a little south of Dan, but not much. I didn't use drywall in my 1,000sf shop ... steel panels on the ceiling and OSB/slatwall on the walls.

Contractor (who is my neighbor) had NO question about putting vapor barrier on the walls and ceilings. He worked very hard to ensure all the air gaps were covered and caulked.

Because of the extreme temperature differential you're going to have in the winter you need to keep the warm moisture air out of the wall and ceiling cavity as much as possible or you're going to get condensation.

At this point, I like the recommendation for poly and then 3/8" drywall.

 

[theoldwizard1]

My question is, do I need a vapor barrier? I live in the northern Wisconsin climate, and have been told I could use expensive mold proof primer as a kind of a vapor barrier , or is it absolutely necessary to get plastic up there and make a proper vapor barrier? I don't plan on running cars in garage either, should I put a vent up? Thoughts? Thanks for your time I am panicking here...

The real question is, are you going to heat it ? Occasionally or continuously ? How are you going to heat it ?

Propane non-vented heaters put out HUGE amounts of water vapor. If that is your plan. then YES on the vapor barrier. If you are only going to heat it ocassionally, don't worry about it.

 

[DC73]

Read the links provided by sands35 in Post #4, then go to GreenBuildingAdvisor.com and visit their Q&A forum. The experts who hang out there can give you better advice.

Building scientists are starting to rethink true vapor barriers and now prefer vapor retarders when the climate calls for one. You might be able to get away with the right paint over the drywall.

From one of the articles linked to in post #4: "Unless you’re building in Canada, Alaska, or somewhere close to the Canadian border, you don’t want interior polyethylene . . ."

Walls need to be able to dry to one side or the other so the worst thing you can do is to have some type of vapor barrier on both sides of the wall assembly. That can potentially lead to a moisture sandwich which leads to rot.

DC

 

[Abeo]

"Unless you’re building in Canada, Alaska, or somewhere close to the Canadian border, you don’t want interior polyethylene . . ."

I live in the northern Wisconsin climate

Second on the poly over existing drywall + 3/8 drywall overaly. Would be the easiest route.