How effective are ICFs as an air and/or vapor barrier without interior or exterior treatments/finishes, or put another way, how much do ICFs rely on interior and exterior treatments/finishes to achieve an air seal and vapor barrier?

It seems that the joints between the styrofoam ICF units would be the weak points.  Any actual testing along these lines?

How about the styrofoam/cement blocks (such as Rastra)?  It would seem that these need both an air seal and vapor barrier.

I am considering ICF for a new house in hot and humid south.

ICF Curious

well not sure how far south and humid you are. but im in orlando florida.

ICF's work as advertised. there is no air or vapor barrier needed on an icf house.

with ICF's you will not only end up with a super tight super insulated building. but it will exceed fortified ratings.

PM me if you would a link to a LEED Silver rated house in central FL. its 3500sqft. there average monthly electric bill is $100.

icf walls, low-e windows, insulated doors, sealed attic. (yes there is an erv) its takes the total package.

but if you only do the walls you will still be alot better off than with sticks, or cmu.

the heat from the day never has time to reach the inside of the house. the mass of that concrete slows the "radiation" down. easiest way i can explain it.

without going and copying some text book.

and vise versa the coolness inside never has a way to escape. and the opisite in winter time of course.

now its not the thermal mass alone or the insulation factor alone or the air and vapor barrier alone.

its combined effort that makes it work the way it does.

then from there the windows and doors are important and the roof/attic.

the entire envelope.

but icf  alone will still be 30-40% more effiecient than stick or brick.  not to mention the added side effect of it making your building have  the strength of a fortress.  :)

you can make a block or stick home tight. it will take alot more time,labor, and if it even comes close to an icf. in the end it will cost a whole lot more. and still will never be as strong. hard to beat a monolithic poured in place steal reinforced concrete. well except with an non removable insulated form. with built in furring strips.

Thanks......I guess it is time for me to do some independent research.

ICF Curious