Worth the quick read too see what the DOE and Building America are saying...
Looking for smart public policy to build (or rebuild) energy-efficient and resilient houses? Look no further than the unvented attic! Don't just take my word for it. Here is what the Department of Energy has to say: Insulating and air sealing along the roof line offers several advantages over insulating along the ceiling deck: ? Energy Savings - An unvented attic is warmer in winter and cooler in summer, reducing the HVAC load. The equipment will be more durable and more efficient, especially if ductwork is in the attic (Rudd 2005). ? Moisture Resistance - The attic will stay dry, avoiding problems with mold and wood rot, and thus can serve as living or storage space. ? Disaster Resistance - Roofs over unvented attics are less likely to be blown off in high winds because the wind cannot readily enter the attic. In addition, a house in wildfire zones is less likely to catch fire from floating embers since there are no soffit vents for the embers to enter. In coastal areas, an unvented roof keeps out wind-driven rain and better protects metal connectors in the roof assembly against salt spray and corrosion (Lstiburek 2006). Unvented, conditioned attics and their advantages have been extensively documented with Building America field tests in numerous states including Minnesota, Massachusetts, and California (Rudd 2005). In the process, builders have worked with researchers to identify combinations of materials that perform well in all climate zones.