Roof May Be Warmer in Winter,
Cooler in Summer
by Douglas Black, ENERSPEC
While performing energy audits on drafty old homes in Michigan, I found one common factor among all those farmhouses, bungalows, and cul-de-sac Cape Cods. The homeowners were paying to heat the outdoors all winter. This was not due to leaving the doors and windows open (although sometimes kids will do that). The attic spaces were hemorrhaging money in heating and cooling costs.
See my Snow Signals blog from a few years back!
Oak Ridge National Laboratory recently field tested a newly designed system to help reduce energy loss through the roof. I learned of this story from Gizmag, an online source for news of the technical, geeky, and cool!
I have shown countless times through computer models that heating and cooling are usually the biggest energy expense for a typical household. They can both be dramatically reduced by simply tightening the entire envelope of the home. After that is accomplished, this new system may be the thing that goes the final mile.
The new roof system design includes a passive ventilation system that pulls air that would have gone into the house from the underbelly of the attic, up into an inclined air space above the roof so it can be carried up and out. It also features controls for radiation, convection and a foiled covered polystyrene insulation. This insulation forms the heart of the system and can be fitted over and between rafters in new constructions or attached on top of an existing shingle roof system without the need to remove the old shingles.
The ORNL team says computer simulations show that poorly sealed heating, ventilation, and air conditioning (HVAC) ducts that leak conditioned air into an attic typically cost homeowners US$100 to $300 per year. Sealing the attic with spray foam can save over $460 a year, but the initial cost is around $8,000.
In comparison, ORNL claims retrofitting the new roof-and-attic design to an existing house could save homeowners around $100 a year, but for an initial cost of about $2,000. While the yearly savings aren’t as high, the significantly lower initial cost would result in close to the same number of payback years for both approaches.