zone 4 specific vapor barrier dilemma

[87jeepwrangler]

in the midst of my garage addition, i have also added approx. 1000 sq foot of 2nd floor addition to my house (living space). in a recent plumbing inspection, my inspector noticed i had started putting some insulation in the ceiling that was not kraft faced (he had said i could start insulation in certain areas in a previous inspection). since i have a lot of non-faced insulation that i got for a song, i was hoping to use it in the ceiling. he and i conversed briefly about it and the different language in the various IRC books, and he said i would need some form of vapor barrier on the ceiling, probably plastic since the insulation wasn't kraft faced. we are using irc 2009 info.

after he left, i headed to the internet for some research and reading and sent him this email...

Tom,

I see the difference in wording from the 2006 to the IRC 2009 manual, however, I am still a little confused. According to the zoning map, bucks county is part of zone 4, but not part of marine zone 4. here is the map... https://energycode.pnl.gov/EnergyCodeReqs/?state=Pennsylvania

That being true, the IRC 2009 code says "R601.3 Vapor retarders. Class I or II vapor retarders are required on the interior side of frame walls in Zones 5,6, 7, 8 and Marine 4."

The code makes no mention of zone 4 (non-marine) needing vapor retarders.

What am I missing?

Thanks,
Rob

his response was...

Hi Rob,

Yes, you are required to have a vapor barrier between the heated living space and the fiberglass batt insulation in the ceilings. Do not get hung up on the limited code information that is available to you. There are many ICC code clarifications and interpretations we as code officials filter through to meet Pennsylvania’s UCC requirements. Some State energy tradeoffs that we apply come through house bills ect. You will indeed need a vapor barrier to pass the inspection.

at this point, i'm not going to argue with him, as i have no interest in making my inspector dislike me. that will only make my lift harder in the long run. so, as i see it, i have 2 options.

put up the plastic and tear it down after he leaves, or leave it up.

living in zone 4, my house (and thousands of other homes in my area) were built over 50 years ago and have never had a vapor barrier whatsoever in the ceiling.

thoughts? will the plastic hurt anything if i leave it up? will it give me problems in the long run?

 

[Gerald O]

If you have a vented attic space above the ceiling then a vapor barrier on the living space side of the ceiling will not hurt and may provide the benefit of keeping condensation from forming in the attic space during the winter. In zone 4 it's a bit borderline. The bigest problem in zone 4 is with adding a vapor barrier to walls that may already have an external vapor barrier. In that case you get a double vapor barrier situation that could do harm rather than good. You didn't state you location, so that makes it hard to give better advice.

 

[bczygan]

You need it.

You are required to have it for a reason.

You should want it.

Just do it.

 

[CNGsaves]

Do the vapor barrier that is appropriate for your area.

RE insulation . . . Don't want to add more work for you, but I'd reconsider using the insulation you got for a "song" as that may be all it's worth (if it's fiberglass).

Check out performance of fiberglass vs blown cellulose insulation. Also check out YouTube video called "The Big Truth" which shows how poorly fiberglass insulation does when actually subject to a fire. The blown cellulose (ie old newspaper ground-up with boric acid added, and fire retardent) kicks the **** out of fiberglass. Also, just for air-sealing and insulating abilities, the cellulose kicks the **** out of fiberglass. For me any new insulation I add with be blown cellulose.

 

[87jeepwrangler]

So even though the IRC book says I don't need it in my zone, the inspector is correct and I should have one?

 

[yeldogt]

The various codes can be very confusing -- but I can tell you that in new construction a vapor barrier has been required for as long as I can remember in Bucks County PA.

The vapor barrier is installed to protect the fiberglass insulation from moisture - this moisture is coming from inside the building -- human activity ... and a lot of moisture is created. Most houses leak --- and any air leaking through the wall/ ceiling will bring moisture that will eventually saturate the fiberglass.

Old houses built without insulation often had various products "blown" into walls/ ceilings -- even packed very tight they were not completely sealed. So the building could breath from both the inside and outside -- and none had plywood.

The problems with vapor barriers began when we started to seal up spaces and then trapped water inside the walls - walls made with plywood and now mostly OSB.

A properly insulated and sealed wall/ ceiling with fiberglass -- can work ... but I would never use plastic to do it. I like building to breath from both sides - with plastic it can only breath from the outside. If you don't have anything the fiberglass can become wet and will not stop air flow.

What did you do in the walls?

 

[bczygan]

So even though the IRC book says I don't need it in my zone, the inspector is correct and I should have one?

Why would you even want to question it?

It's a minor and inexpensive thing. Do you know why it is used?

BTW, unfaced with a plastic VB, properly taped and adhered is far superior to kraft facing.

At this point it is irrelevant whether the inspector is correct or not. He's the inspector.

Codes are complicated.

New ones are always coming out.

It depends on which ones your jurisdiction has currently adopted.

It depends on what changes to the codes that they have adopted, and these can be extensive.

It depends on the emphasis that your particular inspector puts on different parts of the code. No, enforcement is NOT entirely uniform. Your inspector has his own preferences.

So, use this as a learning experience. You could ask how this works to prevent moisture in the building envelope. Most inspectors are very helpful in explaining.

But getting in a discussion with him about whether it is required or not......it's required, by him. Case closed.

You do have one other choice.

Tell him you believe it isn't required and you aren't going to do it.

Then you can look for all the red tags.