Hot climate, cold climate, wet or dry, windy or calm, heating or air conditioning - no matter what. Builders and building scientists know that the greatest enemy of building efficiency is air infiltration and movement of air into insulation. The enemy of building longevity is hidden moisture condensation causing mildew and decay, not to mention the threat to health and comfort caused by these agents. While conventional fiber insulation in the right conditions may achieve thermal insulation with some success, it by its nature of using the air to insulate cannot isolate the air of the two climates. Air is mixed into the fiber with each change in outdoor temperature or wind condition - compromising thermal quality.
Air contains moisture which when cooled, seeks to drop out on a surface as condensation.
This occurs at building sheathing in the heating season and at the back of sheetrock in the air-conditioning season. Efforts to solve these problems have included caulking, house wraps and sealing tape, vapor retarders, venting and foam sheathing, together endeavoring to achieve what we really need - isolation. Climate isolation is the full separation of the climates. No place for moisture.