Air barrier between garage ceiling and living space above
LawrenceMartin
| Posted in Green Building Techniques on
I’m planning to build a “pretty-good” house in climate zone 5b, just south of Denver. My house has an unheated but well-insulated garage below a Great Room above and I am trying to figure out the air barrier. Floor design is, from top to bottom:
1) Laminate floor finish
2) OSB floor sheathing
3) 11 7/8″ TJI w/ cellulose insulation
4) 1″ EPS for thermal bridging,
5) 1/2″ drywall installed using airtight drywall technique.
If my air barrier is on the bottom, using the drywall, will the floor structure/materials allow for the floor to dry to the interior when needed? Or, is my air barrier in the wrong place?
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Replies
Lawrence,
This type of floor assembly is going to stay dry after construction is complete, so drying paths aren't very important.
But in any case, this assembly can dry downward. Most drying of this assembly is by diffusion, not ventilation drying. (Ventilation drying happens in rainscreen air gaps and vented cathedral ceilings, but not in floor assemblies.) The air barrier won't inhibit drying by diffusion, because 1 inch of EPS and drywall are somewhat vapor-permeable.
Lawrence,
One more point: For fire safety reasons, most building codes require drywall in garages to be 5/8 inch thick, not 1/2 inch thick.
Thank you, Martin, for the clarification. And, yes, I will make sure the drywall is 5/8" Thank you for the reminder.