The media relations group for Oak Ridge National Laboratory just released more information about recent field tests by ORNL of a new roof and attic system that keeps homes cool in the summer and prevents heat loss in the winter. The system is explained in the graphic embedded above (click to expand). In addition, I’ve included some graphics below to illustrate more of what the system looks like and how it saves energy.
The system employs a passive ventilation strategy that is expected to cost about $2,000 for a retrofit situation with savings of roughly $100 per year, yielding a payback of about 20 years.
Foil covered polystyrene insulation (with the ventilation gap) is installed over and between rafters for new construction or on top of an existing shingle system in a retrofit. With the new roof assembly, air moves from the underbelly of the attic into an inclined air space above the roof, according to an ORNL statement, so that “heat that would have gone into the house is carried up and out,” said Bill Miller of ORNL’s Building Envelope Group.
In the summer, the temperature of the attic is reduced as a result of the roof detailing and, according to observations by ORNL, the thermal load of the home is thereby reduced. Further, ORNL found improved efficiencies even if the attic floor is insufficiently insulated.
The research and findings are discussed in more detail in a paper, “Prototype Roof Deck Designed to Self-Regulate Deck Temperature and Reduce Heat Transfer,” published by the National Roofing Contractors Association. A PowerPoint of the background research can be found here [PDF].
News 10 in Sacramento, California – Many homeowners suffer from unnecessarily high utility bills, uncomfortable temperatures in the summer, musty smells on objects stored in the attic and condensation on windows and doors during the winter. According to Allan from U.S. Sunlight and Cliff from Eco Attic, these problems can be resolved by simply addressing the home’s attic space. Alan Breidenbach puts it bluntly, “If you don’t ventilate, it can cause mold, mildew and potentially health problems.” He is referring to the need for year-round attic ventilation.
The benefits of active attic ventilation are commonly linked to summer months. The Florida Solar Energy Center has analyzed 21 houses and determined 43% of air conditioning design load is based on elevated attic temperatures which frequently reach 160?F. For this reason, many homeowners quickly look to lower attic temperatures in order to alleviate air conditioning usage.
Despite popular belief, a well ventilated attic is just as important during the winter months. Most homeowners believe a hot attic in the winter months provides a heat barrier to keep the rest of the home warm. Unfortunately, a warm attic does little more in the winter months than to create the perfect environment for mold and mildew. As the warm attic air reaches the cold underside of the house roof, it creates condensation. In fact, according to the Energy Performance of Buildings Group at the Lawrence Berkeley Center, throughout the course of the winter months, a typical attic absorbs up to 220 pounds of moisture. In the spring, the building materials in the attic release the moisture back into the attic, equivalent to almost 30 gallons of water. Moisture in the attic causes these following homeowner nightmares: