Solar Haven is a three bedroom contemporary with an open floor plan. The house's total footprint as measured by the ANSI Z768 standard is 2,938 square feet, of which approximately 2,500 is finished area. The owners occupy the house's Upper Level comprising: Atrium, Master Bedroom suite, Kitchen, Living Room, and Mudroom. The house's Lower Level will be a Bed and Breakfast guest area containing two bedrooms, an office, and a Family Room. The two utility rooms, storage, and a root cellar occupy the remaining square footage.
Beginning in 2Q'2009, Green Build Science will offer B&B lodging to its clients. Guests will be able to experience first hand the benefits of living in an energy efficient, green built home. During their stay, clients will work with Green Build Science to develop their own personalized "green build" plans for either the renovation or new construction of their own residence.
Exceptionally air tight construction: The objective is to have less than 5% of the interior air volume leak per hour to the outside. In typical homes, it is common to see 30% or more of the interior air volume escape to outside every hour.
Passive solar: The house's longest wall surface faces due South. Over 70% of the window area is on the South side. The computer modeling phase searched for the right balance between the window's solar aperture area, window glazing technology, roof overhang, and house's thermal mass. All of these components were optimized to achieve the maximum passive solar heat gain without incurring overheating spikes.
High performance windows: The windows are all triple glazed, filled with argon gas, fiberglass frames, and have insulative performance in the range of R-4 to R-6. The South facing windows are custom built with a low-emissivity thin film coating that maximizes the passive solar heat gain while reflecting the interior's heat back to inside.
Earth bermed: The house's Lower Level floor is a walk out basement, bermed into a South facing hillside. Earth berming saves energy because the heating plant only has to raise the room's temperature relative to the Earth's constant 45 degree temperature rather than the exterior's temperature and wind.
Insulated Concrete Form (ICF) foundation: R-22 insulation
Insulated slab: 4" of rigid board foam underneath the concrete slab
Masonry heater: Solar Haven's primary backup heating system for the nighttime and cloudy days is a wood-burning masonry heater. Unlike a conventional wood-burning stove, a masonry heater is built from several tons of firebrick. A fast burning fire is lite within the firebox and the exhaust gases heat up the brickwork. Long after the fire burns out, the masonry heater slowly radiates its heat over a period of 8 to 16 hours. The masonry heater is expected to provide 70% to 90% of the household's heat during Vermont's most cloudy Winter season, November through January. The firewood is sustainably harvested from the Solar Haven lot's wooded acreage. The total firewood used per heating season is expected to be a little over one cord.
Radiant heated slab floor: The secondary backup heating system is a conventional propane-fueled boiler, delivering heat to the Lower Level's radiant heated slab floor.
After space heating, Domestic Hot Water (DHW) is a household's largest energy consumer. In a typical household, it represents about 30% to 40% of the energy usage. At Solar Haven, the DHW usage has been minimized by installing best in class appliances and fixtures that achieve their tasks yet use the minimum amount of hot water: a front-loading clothes washer, a dishwasher that uses 6 gallons of DHW per use, and low-flow shower heads and faucet fixtures. The solar hot water system pre-heats the hot water before the on-demand propane-fueled combi-boiler raises the temperature, if needed, to its set point of 125 degrees. There are two 4'x10' solar hot water collector panels mounted on the South-facing roof. The solar hot water system has been sized to provide approximately 2/3rds of Solar Haven's annual DHW energy.
Finally, at Solar Haven the electrical energy usage has been dramatically reduced from the typical household's 25 Kilo-Watt-hours (KW-h) per day to less than 12 KW-h per day. Similar as was done for space heating, a variety of energy conservation techniques are applied to reduce the electrical energy consumption to a level that allows the renewable energy system to cost effectively provide the majority of the household's energy needs. With solar photovoltaic systems costing $8 to $10 per "peak watt", an aggressive conservation strategy will save tens of thousands of dollars. The Solar Haven solar photovoltaic system will produce approximately 3,000 KW-h per year, covering about 2/3 of the annual electrical energy budget. In contrast, without applying energy conservation, the 3,000 KW-h solar photovoltaic system output would provide only about 1/3 of the electrical energy budget. Solar Haven's solar photovoltaic system is connected to the national electrical power grid. Consequently, when the system produces more electrical power than the household needs, the power is "net metered" into the grid and credited to the monthly bill. For those times when the system's solar panels are not producing power, the power is drawn from the electrical grid. In the event of a grid black out, the solar photovoltaic system has a three day supply of "critical load" electrical power stored in an array of 16 huge lead-acid batteries. The battery back up allows the household to continue minimal operation of essential components, such as the water well pump, the boiler controls, refrigerator, the kitchen appliances, and the lighting for the high usage areas.
In principle, the solar photovoltaic system could be expanded to achieve an annual net-zero balance. Although in the future price/performance breakthroughs are inevitable, as of today producing 100% of one's electrical needs is not cost effective with the available technologies. Instead, the system was sized to meet the household's critical loads when the grid is offline.
Today, over 110 million houses in America are built on the dysfunctional assumption that energy is cheap and reliable. Until gasoline reached $4 per gallon, few understood that the laws of economics are not kind: when supply can not meet demand the price increases exponentially. The age of the cheap energy is gone. Although Solar Haven is at the cutting edge in building science, there is no technical barrier to having every new home built to the same high performance level as it has achieved. These extra upfront investments pay for themselves in 3 to 10 years, depending on what assumptions you make about the future energy costs. Even in existing homes, it is feasible to apply these techniques within the constraints of the original house design.
Beyond the economics, there is the fundamental satisfaction of becoming energy independent, of having your home secure against the world's forthcoming chaotic events, which in my view are likely to disrupt the nation's energy supply for weeks, months, or even years. You still have time to act, however, all of the signposts that I see suggest that the window is closing. "
George offers a variety of energy related consulting services through his firm, Green Build Science and can be contacted at firstname.lastname@example.org. Lastly, thanks to George for a great dinner!
Photos: The view from the Gross home, front view of the house, George by one set of solar panels, a portion of the power management system, George finds that a cyclocross bike is useful in Vermont