said by aroberti:I've never seen a house that was 100% air-tight -- and even if it were, that would present a whole new set of challenges...
When building his house, a neighbor down the street went with Icynene insulation, and it's about as air tight as you can get without going closed cell. The downside is that it's expensive (about 3.5X the cost of fiberglass) and you are supposed to install air handlers to exchange the outside air because the home is sealed so well (or so said the salesman when quoting me a price).
I decided to go with traditional fiberglass with 2x6 exterior walls and a higher total R-value over the second floor. I just didn't want to get into additional equipment and I had heard of some buildings with interior problems because the house was sealed too well (mold, sickness, etc.) And I just thought it was simply too expensive. I don't think my heating and cooling bills are ridiculous either... 2x6 with vapor barrier has been great at maintaining interior heat and cooling.
My neighbor does like Icynene though... he recommended it and said he would use it again if he built again.