Chicago, IL -- June 9, 2009

dbHMS designed the MEP systems for the Zero Energy Home, which was featured June 7, 2009 on ABC7. The home’s mechanical electrical and plumbing systems are designed to produce more energy than it consumes making it one of the greenest homes in the country.
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The home aims to be the first fully-functional zero-net energy home in the Midwest and hopes to achieve LEED for Homes Platinum Certification. The Zero Energy Home is participating in the USGBC’s LEED for Homes pilot program and the City of Chicago Department of Environment’s Cool Roofs grant program.

Water Conservation

The home’s state-of-the-art water conservation and recycling program includes a rainwater collection and irrigation system along with a gray water collection and reuse system that employs low-flow plumbing fixtures.

A damper diverts the rainwater to a 550 gallon cistern that is located in the basement of the home. The water collected in this cistern will be constantly agitated and circulated up to a water feature fountain in the courtyard. Collected water will be used to irrigate the landscaping around the house. Should the cistern become full, the system will detect this and overflow will divert to the city sewer.

Waste water from the washing machine will be collected in a smaller, 35 gallon cistern, also in the basement, and eventually be reused to flush the two toilets in the home. Before this occurs, the water will be treated with chlorine, pass through two micro-filtration devices, and then be exposed to ultraviolet filtration.

Energy Conservation

The heating and cooling energy system, comprised of geothermal technology, solar-thermal water heating and passive solar and photovoltaic solar panels, is designed to dramatically reduce dependence upon fossil fuels. Engineers predict that every year, this energy system will generate at least as much electricity as it consumes, with an excess being fed back into Chicago's energy pool.

Photovoltaic Solar Panels

The Home will feature a 10kW Solar Photovoltaic System which will consist of 48 solar electric panels. There will also be four evacuated tube Solar Thermal Water Heating panels.

When the panels are producing electricity, any excess electricity not immediately used by the home will flow into the city electrical grid. With “net metering” this means that the meter will turn backward when this is occurring. This is central to the zero-net energy theme. During the warm months of the year, the panels will produce a significant amount of excess electricity, much of which will go directly into the city’s electrical grid. During the colder months, the panels will have a shortfall of electricity, and the electricity sent into the grid in the summer will be bought back in the winter. If the home produces more electrical energy than it uses over the year, the electric utility effectively purchases the excess (at a reduced rate, of course). This is the most efficient use of the electricity generated by the panels, and by foregoing on-site battery storage, energy losses caused by conversion and the relatively short life span of these toxic environmentally unfriendly batteries is avoided.

Solar Thermal System

The Solar Thermal Water Heating Panels are “evacuated tube collectors” covered with tempered glass. A water/food grade glycol mix is circulated up to the panels and absorbs the solar heat that has collected in the panels’ tubes. It then travels down to a heat exchanger where the heat is transferred to potable water stored in the solar storage tank. This hot water is then fed into the electric hot water heater. The electric hot water heater will only turn on when the water fed to it from the solar side drops below a minimum temperature. Amazingly, solar thermal panels are able to heat water efficiently even on cloudy days and through the winter.

The hot water generated by the system will be used for domestic hot water uses and the radiant heating system.

Geothermal System

The Geothermal system consists of an electrically driven water-source heat pump and 3 “wells” that go to a depth of 250 feet. The system is connected to a radiant floor heating/cooling array that runs through the concrete floors of the entire house (including the basement). The system does the work that is ordinarily done by a furnace and an air conditioner, is quite compact and very quiet.

Instead of burning non-renewable fossil fuels to produce heat, geothermal systems rely on the relatively constant temperature of the Earth below the frost line (about 50 degrees F). The 3 wells allow the circulating fluid to “pick up” the heat of the earth and bring it up to the heat pump where, much like a refrigeration unit, a compressor and heat exchanger in a vapor compression cycle are used to magnify this heat gain and distribute it to the radiant system.

For cooling, the process is reversed. As the fluid circulating through the radiant system draws heat from the home, that heat is transferred to the fluid circulating through the wells. The earth then acts as a heat “sink”, absorbing this heat and cooling the fluid as it runs through the loop.

Geothermal systems use less energy because they don’t have to work as hard as traditional heating and cooling appliances. It is much easier to capture heat from 50 degree soil than from the atmosphere where the air temperature may be below zero. During cooling, the relatively cool earth absorbs the home’s waste heat more easily than hot outdoor air.