Vapor Barrier Question - Contractor Talk - Professional Construction and Remodeling Forum

radarboy · 10-12-2009, 02:56 PM

Had a Building Inspector tell me today I need to Visqueen the ceiling if I'm useing loose fill insulation before I drywall. Does this sound right?

**genecarp** · 10-12-2009, 03:09 PM

Not neccasarily visqueen, but 4 mil plastic sounds correct. G

Ancient Rocker · 10-12-2009, 05:54 PM

I think we missed something. To hold the loose fill before drywalling, you must have something there. If he said to put plastic up, hang the drywall, then loose fill, it makes a little more sense. I have not seen plastic vapor barriers in Illinois for at least 20 years. If your local code requires it.all you can do is comply. Vapor barriers are only what they imply,to trap moisture so it can deteriorate the cavity and promote mildew,mold and water damage. I would ask for a code book before putting up ANY plastic vapor barrier.

oldrivers · 10-12-2009, 07:19 PM

Quote:

Originally Posted by radarboy

Had a Building Inspector tell me today I need to Visqueen the ceiling if I'm useing loose fill insulation before I drywall. Does this sound right?

uhhhhh yes, hes the inspector . 99% of the time he is right. sheetrock acts like a conduit of moisture so it should be covered to keep insulation dry.

jaros bros. · 10-13-2009, 07:29 AM

"Vapor barriers are only what they imply,to trap moisture so it can deteriorate the cavity and promote mildew,mold and water damage. I would ask for a code book before putting up ANY plastic vapor barrier."

Vapor barriers are only one part of the system. Without proper insulation and an air exchanger you might have those problems. Done properly this issues will never be there.

mics_54 · 10-13-2009, 10:36 AM

This is a joke post ,right? Where's the camera???

AARC Drywall · 10-25-2009, 11:29 PM

Here in BC we by code have to have 6 ml vapor barrier polly.

bwalley · 10-25-2009, 11:35 PM

Quote:

Originally Posted by radarboy

Had a Building Inspector tell me today I need to Visqueen the ceiling if I'm useing loose fill insulation before I drywall. Does this sound right?

In Florida on ceilings we don't use vapor barrier, with either loose fill or batt's.

In the attic on walls like a vaulted ceiling we will use kraft faced batts.

Have the inspector show you in the code book.

BTW where are you located?

cleveman · 10-26-2009, 07:05 PM

In Iowa this is not done, but I understand it is the norm north of here. May save on humidification in the winter. I think there are positives and negatives with this practice.

kubie · 10-26-2009, 07:13 PM

no polly needed on the ceiling in WI. some put it up, some dont

jeffatsquan · 10-26-2009, 07:40 PM

I think the theory is that warm moist air inside the home will migrate to the colder exterior side of the wall cavity, at which time the air will condense causing the the vapor to turn to liquid form and wet your insulation. You can chose not to believe this, or do like the best builders in our area do and use 12 mil. poly.Your climate my cause different scenarios

nEighter · 10-26-2009, 09:13 PM

isn't any in Kansas either.

kevjob · 10-26-2009, 09:48 PM

Here we need a vapor barrier, be it plastic, kraft faced or encapsulated R-38 for ceilings.

cleveman · 10-27-2009, 05:41 AM

I believe my hvac guy told me never to do it, unless I want the sheetrock on the ceiling rotted out. However, I would like to try it. It would be nice to keep the humididity inside in the winter.

Anyone care to comment on the potential to rot the sheetrock?

Anyone care to comment on improved humidity levels in the home in the heavy-furnace running months? I like to keep the humidity at 55%. Ice on the windows be damned. Our skin and nasal passages are more important.

mics_54 · 10-27-2009, 12:07 PM

A vapor barrier will not cause sheetrock to rot. Moisture might though. If you live in a hot humid climate with no insulation in a structure with a conditioned space you could get condensation on the inner (inside the walls or ceiling) surfaces of the drywall...with or without a vapor barrier. However that isn't real common because usually the dew point isnt reached in those conditions.

That being said ..the point of a tight house is to control the environment. In a house that has air infiltration the environment within the house cannot be controlled as effectively as in one with no air leaks.

Note I didn't say "cost effectively" I merely said "effectively" To control the environment in a tight house you must have the capability to manipulate the air characteristics. The air quality is dependent upon 3 aspects... temperature, humidity and whats floating around in it.

You can no more control these three things in a house with no impermiable membrain than you can in a house with the windows open.