Recently local natural gas supplier National Grid initiated a program to track users' energy consumption in relation to their neighbors.
Each month, consumers get a rolling 12 month summary of their usage compared to the average, and the 80th perctile, of his neighbors. Neighbors are defined as "approximately 100 occupied nearby homes that are similar in size to yours and have gas heat." On my report that average was 5,340 sq. ft.
The results for winter 2010-11 are in, and it appears that the Energy Tab house is among the most efficient -- and quite possibly the most efficient -- in the 'hood. For the period December through February, consumption of fuel is below. (I've pro-rated our usage to adjust for our size differential vs. the average home.)
- Average home: 1,545 therms
- 80th percentile home: 1,134 therms (73% of average)
- Energy Tab home: 695 therms (45% of average)
Besides thanking the Academy, I'd attribute our success, in rough order of contribution, to the following design elements:
- 7-to-10 inches of styrofoam insulation, in the form of construciton with Structural Insulated Panels (SIPS), as well as EIFS cladding.
- A high-efficiency condensing boiler.
- Modern windows. In our case these are European-style windows with a value of R-5, which slightly better than U.S. norms, or code.
- Lots of south-facing windows, providing plenty of solar gain -- but an energy liability in the summer.
- An Energy Recovery Ventilation System, which also serves to vent the bathrooms.
- In-floor radiant heating. Honestly, I have no data to support the notion that heat delivered to the floors is more effienct that that delivered elsewhere, but I expect it helps.
Yet jealosy can take root even among the winners.
My window supplier tells me that they now make European style triple-pane windows delivering R-10+ performance for a price premium only 12% more than their double-pane standard. Windows like that probably provide more insulation than the walls in the average old New England home.
And a new line of hydronic pumps has just come out promising 66% reduction in the electricity needed to push all that warm water through radiant floors. I don't know of those pumps use a lot of juice or not, but 2/3 reduction is a huge gain.