Can you get air-tightness without a polyethylene barrier?

[Danjoh99]

Is anyone aware of a building that has achieved the 0.6 ACH-50 rating
without using a plastic polyethylene barrier inside the wall and
roof?

We've talked about using the exterior sheathing as the air barrier
(caulking or taping every crack between panels), and using the
interior sheetrock as the air barrier (which is vulnerable to
electrical outlets, light fixtures, etc.). Do these methods, well-
executed, easily produce enclosures that meet the 0.6 ACH-50
standard? Do we have examples?

In our climate, I'd rather not use a plastic vapor barrier in order to
have an effective air barrier.

Thanks,
--Dan

[bronwynb]

Dan,

Many of the projects mentioned at the Duluth conference used the OSB
sheathing as their air-tight barrier and did not use a poly barrier.
The OSB was sealed with tape and mastic, similar to that used on
ducts. One product mentioned was: Thoroseal (www.thoroproducts.com.)
There was also some debate as to where to locate the air barrier -
some felt it had to be on the inside, while others (Marc Rosenbaum et
al) felt that the exterior worked just as well and was easier to
achieve.
This is certainly another discussion thread, but, being the window and
door sales person that I am, I would advise that you make sure the
windows and doors you spec achieve sufficient air-tightness ratings.
No point in spending hours of research and labor in getting your walls
and roof sealed if the windows and doors leak!

[George J. Nesbitt]

There is much confusion between air & vapor barriers. A good vapor
barrier is not an air barrier unless all the joints are sealed. I think
some of the moisture problems of the past have been due to good vapor
barriers reducing the ability of walls to dry, but being bad air
barriers, letting lots of moisture in.

I would prefer to not see vapor barriers in houses, unless they are in
the correct place, and are air barriers too.

I would also prefer to see an air barrier on all sides of walls! The
exterior is easier because there are less joints and penetrations than
the interior.