The entryway works as an airlock, keeping cold winter air from flooding into the interior of the building when the front door is opened. The double-pane, two-layers-of-Heat Mirror®, krypton-filled storm door is typical of the gas-filled superwindows found throughout the building. It insulates more than three times as well as triple glazing, or eight times as well as the wooden door inside. Indeed, on sunny winter days, the inner door can get so hot that its varnish starts to bubble! Even newer and better glass stormdoors, about four times as insulating as triple glazing (because of an additional heat-reflecting coating inside the outer lite of glass), cover the building's other three exterior doors.
A low-hanging beam just outside the front door helps save additional energy. The beam shades the door in summer, when the sun is high; in winter, when the sun is low, it allows the low winter sun to shine in. The overhang also shades the metal cooling fin that keeps refrigerated food cool without electricity for about half the year.
The dining room table serves as a workstation, a conference area, and a place to eat—often all three at once.
The overhead lamps in various locations illustrate the immense variety of compact fluorescent lamps. Each uses 20–25 percent as much electricity as an equivalent incandescent bulb, lasts 10–13 times as long (and thus pays for itself just by avoided maintenance costs, making its electric savings better than free if maintenance time is valued), and over its lifetime will keep up to a ton of carbon dioxide out of the air. In 2009, nearly all the compact fluorescents were replaced with even more efficient LEDs.
Several noteworthy devices in the kitchen save energy without compromising convenience. The hood over the stove has an air-to-air heat exchanger. Outgoing warm air heats incoming cold air, saving energy.
Until 2009, the building used a propane stove and two types of cooking vessels that save ~30–40+ percent of the fuel normally needed: an English "Simplex" copper kettle (whose heavy copper coil and rim entangle hot gas so most of the heat goes into thee water rather than escaping around the sides to heat the kitchen) and Swiss Rikon walls with insulating double walls and double lids. In 2009, the stove was replaced with a renewably powered Swiss electric cooktop whose specially integrated pot design cuts power use to ~60% less than an induction cooktop's.
The SunFrost™ refrigerator/freezer uses only about 8 percent of the energy used by a standard fridge of similar capacity. The freezer uses about 15 percent of the energy used by an ordinary freezer. The appliances' designer eliminated a number of energy-wasting elements common on standard models.
For example, standard refrigerator/freezers have their compressors, which radiate heat, on the bottom. Because heat rises, SunFrost™ designers placed the compressor on the top, making it easier to keep the unit cool.
Conventional refrigerators also have cooling fins attached to the back of the refrigerator that warm up the box. The SunFrost models' cooling tubes are instead on top. In addition, the refrigerator's liquid cooling circuit is linked by a small, gradually rising copper tube to a cooling fin on the outside wall of the entryway. When the outside air is cold, the refrigerant gas rises up, condenses back to liquid in the fin, runs back down the pipe by gravity, and keeps the compressor off. This saves about half the electricity that the refrigerator would otherwise use annually.
Conventional units have heated door seals that prevent condensation, but heat up the inside of the refrigerator and freezer. SunFrost instead employs seals of a material that repels water. This unit currently uses about 85 kilowatt-hours per year. Standard refrigerator/freezers made around the same time use about 1,200 kilowatt-hours annually.
This refrigerator/freezer also has thicker, higher-quality insulation than standard models. This gives the appliance superior performance, but it makes the units less compact overall. More advanced kinds of insulation that are more effective, yet much thinner, have since become available.
Other Energy Saving Kitchen Devices
The faucet in the island sink has at times been equipped with a device that discharges water in a laminar flow. This smooth flow enables a low volume of water to wet hands or vegetables thoroughly without bouncing off, yet still permits full flow for filling pots quickly. This reduces the amount of heated water needed. (This device is not currently in place—it was broken during a routine cleaning and has not yet replaced.) The Swedish Asko dishwasher washes and rinses only until the water comes out clean, then moves on.
This image illustrated Amory (and Judy's) books lit by the sun during a deep-winter midmorning snowstorm, thanks to daylighting distributed by Solatubes carrying light from rooftop Fresnel collectors on the opposite side of the adjacent utility room.
Underfloor radiant heating and domestic hot water are distributed by this low-friction piping, which reduces the normal pumping power by an order of magnitude. Aspen Solar Systems (Mike Tierney), Resource Engineering Group, and Alex Hill (LEAX Controls, Inc.). Steca solar controllers by SunEarth. White magnetic flowmeters by ABB.
Washer and Dryer
The ~40%-more-efficient Maytag Neptune clotheswasher was replaced in 2009 with even more efficient models made by Whirlpool. We very rarely use the dryer, thanks to the adjacent passive-solar drying clerestory.
Batteries & Inverter
Most photovoltaic systems charge a battery bank in the daytime and use the power at night. Instead of losing a fifth of the solar electricity going in and out of the batteries, we sell all surplus electricity to the grid as it's produced to displace coal-fired power plants. The 65-kWh industrial-style lead-acid batteries "float" fully charged (so they last indefinitely), and are there only to provide autonomy if the utility grid fails.
The German "Sunny Island" controller next to the batteries makes the "Sunny Boy" inverters (behind the solar hot-water panels at the north edge of the roof) able to power the building without interruption through grid blackouts, then when grid power is restored, seamlessly detect, resynchronize, and reconnect.
Sol Energy installed these controllers to enable the house to "island"—run without the grid—using the industrial lead-acid batteries (normally floating, not cycling) to ensure autonomy.