Energy Conservation Systems

The three main uses of energy in a traditional house are space heating, water heating, and air conditioning. Yet a traditional design wastes a high proportion of the energy used for each purpose.

The Wentworth Project is designed to reduce the everyday waste of energy in a home. The project uses several innovative technologies to generate its own energy and use it more frugally.

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Solar Windows

A Solar4Gain widow vents the heat between the exterior and interior thermo-panes into the house, allowing the home to acquire solar gain with low-iron or conventional glass and conserve those gains with a "Low E" glazing. The window is tilted even in a vertical frame to permit better collection of sun light in winter.

The window is self regulating and requires no external controls once set (to vent or not). Venting allows the window to use a better "Low E" rating on the glass to conserve heat gains.

Window with SSEP awning.

The fixed awning is our Split Solar Energy Panel, the photovoltaic (PV) exterior skin with a glycol filled inner core divide sunlight into electric and heat energy. It doubles the energy harvest capability per square meter, prolonging PV life and the efficiency range. The underside is a concave mirrored surface to redirect reflected light into the window.

The panel keeps the interior from over-heating during the few months when the sun is high in the sky. The sunshades perform a number of tasks with the same low-tech form.

The Sun2Heat version has only two independent panes like those used in greenhouses. It does not vent but will allow tilt action to ventilate thus allowing maximum gain. Snow loads cover all but vertical surfaces in the Canadian winter, therefore an inclined window in a straight wall was designed. Angling the glass reduces reflection and refraction of light in the winter.

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Hot Water System

Water enters a conventional home at an average of 7°C (45°F) and is then heated to 60°C (140°)F in a hot water tank. Water draining from a tub or shower is on average 38°C (100°F). But none of this heat is recovered; it simply drains away in the pipes and is carried away from the house.

The Wentworth Project uses conventional copper and ABS (plastic) plumbing, but saves substantial energy in hot water heating, which is the second-largest use of energy in the typical Canadian home.

Grey Water Heat Exchangers

To reduce the amount of energy required for heating water, heat exchanges were designed to take advantage of the existing heat in grey water, e.g. waste water from baths and showers. Two simple designs for grey water heat exchangers were devised for the Wentworth Project, one tubular and one based on a drum.

Tubular Heat Exchanger Construction

The tubular unit fits between floor joists in the basement, using space that is normally wasted. It is constructed from copper tubing with pipe fasteners soldered on in the form of a cross to keep the 1/2-inch copper pipe in the center of a 2-inch ABS tube.

The copper pipe carries cold water to the water heater, while the ABS tubing is the grey water drain. In effect, the incoming cold water is "pre-heated" before it arrives at the water heater, which can be either conventional or solar.

Three lengths of copper inside ABS is an optimum design. All connections are conventional ABS, except where the copper exits through a drilled cap, which is then resealed with aquarium silicone. All copper connections are done outside the ABS tubing to prevent any chance of a leak. A small self-cleaning filter keeps debris out of the heat exchanger to prevent gumming up.

Drum Heat Exchanger Construction

The second heat exchanger design involves copper tubes suspended in the upper two-thirds of a plastic 45-gallon drum. Used plastic drums can often be found at low cost.

The gray water enters the drum via a standard 3/8-inch copper pipe, which splits into three for increased heat transfer. Three coils of copper pipe are held in place inside the drum by copper straps that act like "fins" to distribute heat to the drum.

On the exit side of the drum, the manifold is reversed so that the three copper coils are reunited into one pipe.

The grey water drains through the copper pipes and its waste heat is transferred to water in the drum. The drum stores the pre-heated water before it goes on to the water heater, which can be either conventional or solar.

Two insulated drums hooked in series will provide the best performance. Stacking the drums reduces the space required.

The Bottom Line

An entire tubular unit installed by a handyman costs less than Cdn$300. Building a single drum heat exchanger costs about Cdn$110; a two-drum unit will be twice as much.

The tubular heat exchanger is best for showers, while the drum is best for baths. In either case, the savings will be between Cdn$300 and Cdn$600 per household per year.

After passing through the heat exchanger, cooled gray water is good for washing your car or watering gardens, lawns, or orchards. Warmer water with soap residues actually promotes plant growth better than cold well water.

Gray water is safe for irrigating crops and watering lawns where pets and children play. But it is best to use cooled gray water via drip or subterranean irrigation, not a sprinkler. This eliminates the risk of aerating any pathogens from family members through a sprinkler. Sprinklers also tend to burn crops or lawns, since water drops form miniature magnifying beads on leaves.

Gray water may also be used to replenish an aquaterrium, or be use for a water garden. Water gardens are a decorative feature with several pluses: they can add security to homes by restricting access, and also give firemen a ready source of water in a worst-case scenario.

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Heat Conservation

Contemporary flue designs are not good at keeping heat in the home and allow much of the heat to escape up the chimney. The Wentworth Project uses both a thermo-wall and a geo-therm to conserve heat that would otherwise be lost.

Thermo-Wall

A thermo-wall is a thermal mass around the furnace and each wood stove that keeps the heat inside the home that would otherwise escape up the chimney flue.

In the Wentworth Project, these walls are built from cinder blocks filled with concrete. Many are faced with scrap marble tiles that were recovered before they went to landfill. Each thermo-wall contains a chimney, plumbing stacks, and electrical conduits that run out of sight between floors but still provide easy accessibility.

A thermal wall works like a "heat battery" to absorb heat from the room during warm days and release heat into the room during cool nights. This helps keep the house warm during winter and cool during summer.

(Above) Many thermal walls at Wentworth are finished with
marble tiles recovered before they were sent to landfill.

(Above) Ari describes the thermal wall construction. Each
wall includes electrical and plumbing runs, and a sprinkler
system to help keep stones cool in event of a chimney fire.

(Above) Closeup on thermal wall, showing rough stones
recovered from quarries. Anti-earthquake bolts will help
hold them in place during an earthquake. Smaller stones
and mortar will be added to finish this wall.

Geo-Therm System

A geo-therm system uses the constant temperature of the earth to regulate the temperature of a building's incoming air. This provides cooler, less humid air in summer and warmer air in winter. A geo-therm can use the mass of a foundation for heat storage.

In the Wentworth Project, the geo-therm uses the mass of the foundation of conventionally-poured concrete, a basement wall, and the back fill to raise the temperature of the air brought into the home.

An underground system of ducts run on a fraction of the energy required in a conventional heat exchanger, providing fresh air to the home in winter and eliminating the need for air conditioning (the third largest energy use in many homes).

Geo-Therm Construction

Installation is inexpensive if done before backfilling during construction.

A bottom cloth-covered drain is laid in gravel, with two more cloth-covered drains added on top. Each drain is separated by about 18 inches from one another, and the top two are at least 6 inches above the bottom drain. This ensures that water does not back up into the ducts. These ducts are covered by another 12 inches of river pebbles or crushed gravel and a final layer of sand before the backfill is added.

Air is sent into the ducts by 12-volt automobile radiator fans housed in an tower placed above grade. A bug screen and louvers keep pests out of the tower.

Once inside the ducts, air is dehumidified by the lower temperature in the tubes. The condensation drains through the duct walls, then the gravel, and finally the drain. This system provides only marginal cooling, but the outflowing air feels substantially cooler due to its lower humidity.

Excess hot air can be vented from the house in summer through roof vents with a 12-volt fan. The l2-volt fans can be run off the photovoltaic panels and batteries directly with no need for a step-up inverter.