Earth-Berm Construction: House is bermed on the north, and partly on the east and west sides, with poured concrete used only in slab and walls underground. Berming provides cool surfaces for the bottom floor in summer, less heat loss in winter, and a cold storage area for food.
Superinsulated Tight Construction: The house is built with high R values (R = 40 in roof R = 27 in walls; R = 3.3 for windows (Anderson HP windows); R = 16 under the slab; R. 6 for doors). Six inch studs with 6 inches of fiberglass plus one inch of foam insulation on the outside of the house provides R = 27. Sealing, weatherstripping, a vestibule, and casement windows provide a very tight envelope estimated at n = 0.03. Attic entryway is sealed and insulated. Sealed Tyvek is used over the insulation in the attic. The heat loss value for the house is about 3 Btu/ft2/DD, about 1/3 the heat loss of an average house. Envelope loss is about 45 million Btu's.
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Passive Solar Design: South Window Glazing Every major room on the south side has large 5 ft x 8 ft casement windows. The house has 200 sq. ft. of south facing windows, excluding the greenhouse. This represents about 8% of the total floor area of 2400 sq ft. E (29 sq ft.), W (20 sq ft.) and N (17 sq ft.) sides have much smaller window areas. The south-facing windows provide 20 million Btu or about half of the remaining heating load over the winter. |
Daylighting: All rooms except the bathrooms have natural lighting from 2 directions. Rooms used in the daytime have south-facing windows, providing ample natural light even on fairly cloudy days. Semi-open design allows light transfer and air movement between spaces. Efficient Lighting: Most fixtures use highly efficient fluorescent or CF bulbs. Efficient fluorescent valence lighting is designed into the living room, dining room, and rooms downstairs. Task lighting used at desks and workplaces. Passive Cooling: Two-foot overhangs (roof overhang and cantilevered overhang) provide shading over all south windows. An east side screened porch roof provides shading for the 15 sq ft. of glass on the door to the porch. Reflective barriers are used on the west windows as needed until deciduous trees planted on the west side shade the windows in summer. Attic is vented by continuous cave and roof vents. House foundation is bermed fully on the north and partly on east and west sides, keeping the downstairs very comfortable even in the hottest weather. Openable casement windows allow large openings to provide substantial area for ventilation. Two double-hung windows (one upstairs and one downstairs) are designed to be used with sealed window fans.
Efficient Spatial Design: House is relatively small in size (2400 sq ft. total, 1800 sq ft. in livable space with 600 sq ft. in furnace room and basement storage areas). Design provides for rooms used in the daytime to have natural lighting and efficient flow patterns (washer/dryer next to bathroom adjacent to bedroom; hallways for movement between rooms; vestibule with entry closet, easy access to porch and deck dining, carport and entrance convenient to kitchen, greenhouse convenient to workroom and garden, etc).
Efficient Appliances: Appliances (refrigerator, freezer, clothes washer, clothes dryer, dishwasher) are relatively new and energy efficient. There is a solar clothes dryer (clothes line) outside, and an inside line in the furnace room. The electric clothes dryer is rarely used. The total electricity usage averages 300 kw-hr per month, about half the average household.
Active Cooling: There is no use of or need for air-conditioning. Two double-hung windows (one upstairs and one downstairs) provide for sealed-opening window fans. Only the upstairs fan is installed in the summer, and it is needed only during prolonged hot spells.
Green Material Use: Recycled plastic flooring (TREX) used for deck construction. No lead used in solder, no lead paint used, low VOC caulks and paint used. Environmentally sound products used for washing/cleaning. Half of concrete typically used in basement eliminated by design. No asphalt used (gravel driveway, mulched walkways). Sealed combustion furnace eliminates materials for chimney. Carport eliminates need for materials for enclosed garage. No carpets.
Energy Management: Temperature reduction to 60 degrees at night, 68 degrees in daytime, and lowered temperatures when no one is home. Zoned temperature settings (5 thermostats). Minimal use of electric clothes dryer and dishwasher. Cold water clothes washing detergents used. CF, fluorescent and task lighting used extensively. Night venting with window fan, and day close up for very hot weather. Reflective foil barriers used on west windows for summer hot days.
Downstairs Storage Room:
Heat Recovery Ventilator (Air.to-Air Heat Exchanger): Provides about 80% heat recovery of the thermal energy in outgoing warm air to preheat the incoming cold air. Provides an air exchange rate of about 0.3-0.5 air changes per hour. Outgoing stale air is vented from the bathrooms, eliminating the need for bathroom fans. Indoor air pollution and humidity are controlled by low, high and intermittent fan settings, as well as a humidity set point.
Thermal Mass: The existing basement slab (insulated) plus tile provides additional thermal mass to store daytime solar gains and release the heat at night. Existing furnishings, sheetrock, etc. also provides substantial thermal mass to prevent overheating during sunny days and to store the energy for later use at night. Daytime highs never exceed 75 degrees. Nightime temperatures seldom drop to the thermostat set point of 60 degrees; often it drops 3 degrees even if freezing.
Food Storage: An extended production season minimizes storage need. Isolated basement room provides root cellar for cold storage of squash, potatoes, sweet potatoes, onions, shallots, garlic, apples and tomatoes throughout the winter. Freezer provides storage for fruits and vegetables. Food dryer provides for long-term storage of dried tomatoes and fruits.
| Photovoltaic Solar Electric System: A 2.5 kW system (about 240 sq ft.) of Evergreen polyciystalline solar cells (12% efficiency) provides DC electricity to an inverter and then to a Net Metering system. Meter runs forward and backward. System sized to provide about 3600 kWh per year, providing 100% of yearly electrical load. The inverter and DC disconnect is seen in the food storage room. The system cost $8900 including a monitoring system after rebate and tax credit. Check webpages in NY www.nyserda.org/energyresources/photovoltaics.html or the NJ BPU's website (www.njcleanenergy.com/ ) for details about rebates and list of approved installers. A Green Tag program now provides an additional rebate based on kw-hr production. (Current rates in NJ are about 15 cents per kWh of solar electric production -- see www.njcep.com/srec/ for current information). |
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Downstairs: Workroom and Greenhouse
Attached South-Facing Greenhouse: A 8 ft x 12 ft attached solar greenhouse (unheated) provides additional heat gain on cold, sunny days, as well as the option to vent unwanted beat gain on warmer days. 240 gallons of water storage and insulated slab provides heat storage that typically keeps GH 20 degrees above minimum ambient temperature. The additional south glazing area of about 100 ft2 brings the south-collecting area up to 12% of floor area. Useful heat gain over the winter is estimated at about 5-7 million Btu. The greenhouse is used for vegetable and herb production in the fall, winter and spring. Greens are grown in the winter. For passive solar gains, it is especially useful in late winter and spring when the 2 ft overhangs over the windows blocks a lot of sunshine. A small fan on a timer enhances the heat transfer into the house.
Downstairs: Furnace Room
Efficient Backup Boiler: A 90% efficient oil-fired boiler provides backup heating for space and water heating. The system is a sealed-combustion unit, with no chimney needed and no potential for downdrafting combustion gases and carbon monoxide poisoning. The unit vents through the basement wall to the N side of the house. Burnham and Energy Kinetics (System 2000) make the two highest efficiency small oil burners (See www.aceee.org for efficiency ratings).
Efficient Heat Distribution and Controls: Pumps distribute furnace heat to the hot water tank, to the radiant heating tank, and to the upstairs baseboard heating system. A 40 gallon radiant heating tank provides low temperature (100-105 F) water to a radiant heating system imbedded in an insulated slab in the basement and to the upstairs bathroom. The rest of the upper floor uses hot water baseboard heat. There are a total of 5 heating zones in the house run by separate thermostats (3 upstairs and 2 downstairs).
Solar Hot Water Heater: The propylene glycol solution in the two 4 ft x 8 ft panels is circulated by a small 12 volt DC pump with electricity provided by a small 15 watt PV panel. A small heat exchanger circulates the heat from the glycol to an 80 gallon tank by natural thermosyphoning where it then feeds the regular 40 gallon hot water heater. The system provides 10 million Btu's per year, about 75% of the hot water load for the year. Provision is made to bypass the regular tank entirely if desired (used in summer operation). System is made in Canada by Thermodynamics and sold in the U.S. by distributors (Solar Works is one distributor in the NE). There are other manufacturers of similar systems such as Heliodyne.
Indoor Air Pollution: The house has radon collection pipes in gravel below slab and a passive vent stack to the roof., giving ambient radon readings. The AAHE reduces excess humidity and indoor air pollution. No combustion appliances used in the house (no carbon monoxide downdrafting possible) No indoor carpeting is used (wood and tile floor surfaces). Source reduction - no toxic cleaners or materials used. Kitchen fan vents as needed (window opened)
Bathtub Heat Recovery/Beat Exchanger: Used warm bathtub water is routed and stored in a 40 gallon heat exchanger where incoming cold water to the solar tank is preheated whenever hot water is used. The heat lost from the heat exchanger to the basement helps to heat the house in the heating season. Water can be diverted for outside uses in the summer (graywater reuse) if desired.