Currently, I have blown-in fiberglass insulation in my attic which is not nearly what is recommended. So I need to add insulation. Recently I have read several articles promoting the use of expandable spray foam insulation. This foam is applied directly to the underside of the roof deck and to the gable ends. All attic vents(soffit and gable), are sealed and covered with foam. This process, in effect seals or "conditions" the attic. The proponents of this method say that it is superior to having the attic floor insulated as in conventional insulation methods.
Does anyone have any experience with this method of insulation? What are the pros and cons?