Contractormag 1374 Ravenswoodheatpump 0

Home is designated to attain LEED Platinum, net-zero energy status

Aug. 1, 2009
When Michael Yannell decided to build a new home for himself in Ravenswood, a north side neighborhood of Chicago, he wanted his home to be revered as a sustainable residential building standard, which will most likely achieve U.S. Green Building Council LEED Platinum certification and net-zero energy status, meaning the home will produce more energy than what it consumes.

CHICAGO — When Michael Yannell decided to build a new home for himself in Ravenswood, a north side neighborhood of Chicago, he wanted his home to be revered as a sustainable residential building standard, which will most likely achieve U.S. Green Building Council LEED Platinum certification and net-zero energy status, meaning the home will produce more energy than what it consumes.

When planning the house design — the house sits on a 5,413-sq.ft. lot, is 2,675-sq.ft. and has a footprint of 1,770-sq.ft. — and mechanical systems with Farr Associates, designer, and Goldberg General Contracting Inc., Chicago, AA Service Company, heating and cooling contractor, Northbrook, Ill., and dbHMS, design and building engineer, Willow Springs, Ill., Yannell focused on using a combination of energy-producing and energy-reducing strategies.

“Obviously, HVAC is the largest area of energy consumption in a home,” said Yannell. “I wanted to minimize the home's individual contribution to carbon and other green house gas emissions, so we went with the most efficient systems possible, boosting geothermal with solar thermal for heating, solar thermal water heating, passive solar heating, natural ventilation, geothermal cooling and a 10kW PV system.”

An integral part of the closed-loop geothermal HVAC system is a 5-ton WaterFurnace Synergy Heat Pump, which produces hot water, or chilled or hot air. TekMar Tn4 thermostats control the heating and cooling in four different zones throughout the house, and the lower level, den and garage are controlled by a Tekmar 541 heat only thermostat. Three wells, located 250-ft. underground in the southwest yard provide 5 tons of capacity and are connected to the heat pump. Each well contains a closed vertical loop of HDPE (#2 plastic) piping that circulates fluid via the electric pump system.

The primary function of the heat pump in the winter season is to generate 120ºF water for the radiant floor system, which was installed throughout the entire home, including the basement. Outdoor temperature must be below 65ºF for the heat pump to generate hot water.

According to Shawn Mansfield, AA Service Company, radiant flooring was used in the house since it is a more efficient means of energy transfer.

“Small lines carry the Btus to all areas,” said Mansfield. “Conduction is used to transfer the energy into the mass, and then the mass radiates the energy to the space. The home’s mass is one of its design features, due to the home’s mass it can be used to store energy during the day and re-radiate that energy at night.”

When the thermostats’ set temperatures are not met by the radiant system, the heat pump stops providing hot water to the system, and instead, provides warm air into the ductwork system. In addition, the north walls of each wing of the house feature an interior mass wall/plenum air return system that allows heated or cooled air to pass along the front- and back-sides of the mass wall, and is then re-circulated through the house to aid in keeping the home a comfortable temperature. A forced-air cooling system is the only cooling system used in the home and works with the air-to-water heat pump during the summer months.

Solar thermal water heating panels, located on the roof, have been installed to heat domestic water that is stored in a solar storage tank. The water is then fed into the electric water heater. The electric heater will only turn on when the water drops below a minimum temperature. Also, through design integration, the water heating panels boost the radiant heating produced by the geothermal system with the use of a heat exchanger.

There is also a solar photovoltaic system, consisting of 48 solar electric panels on the roof that generates a maximum of 10kW of electricity. During the summer, any electricity that is not used will go into the city’s electrical grid. During the winter, the panels will not produce as much electricity, so the electricity sent into the city’s grid will be bought back. Over a year’s time, if the house produces more electricity than what it used, the electric utility will purchase the excess.

“When the panels are producing electricity, any excess electricity not immediately used by the home will flow into the city electrical grid,” said Yannell. “This means that the meter will turn backward when this is occurring, which is central to the zero-net energy theme.”

Also unique to the house is a rainwater collection system, low flow plumbing fixtures and a grey water collection reuse system, the first residential grey water system in Chicago, which conserves water.

“The plumbing system was designed to maximize the efficiency of the hot water heating system, by circulating the water throughout the house, and over sizing the storage of hot water, so that the system could be maximized on sunny days,” commented Yannell.

According to Kevin Lowe, K. Lowe Plumbing Inc., the plumbing systems of the house are broken down into three phases: a basic conventional plumbing system, laundry waste water and rain water, and all systems are set up with backflow preventers and solenoid valves.

The conventional plumbing system’s water is used for showers, lavatories, and kitchen and laundry facilities. Low flow plumbing fixtures installed in the home are 1.5 GPM showerheads, 1.5 GPM lavatory faucets, dual flush toilets and a 1.5 GPM kitchen faucet.

The laundry waste water is recycled and is supplied to the toilets. A lint filter removes any large dirt patches, lint or thread, and then water goes through a chlorinated tablet feeder. The water is stored in a 35-gal. cistern. An ultraviolet filter and two cartridge filters purify the waste water before the water supplies the toilets. If the cistern fills up due to low toilet usage, excess water will enter the sanitary waste system and flow out to the city sewer through an installed bypass.

Yannell also conserves water by collecting rain water through a roof drain and storing it in a 550-gal. tank in the basement. A Vortec filter removes all solids before the water enters the storage tank. The filtered water is used for the irrigation system, fountain and pond.

At the moment, the house is going through the USGBC LEED certification process and should receive LEED Platinum certification in August, receiving 114.5 points (per LEED for Homes Pilot version 1.11a) out of 128 total points, the most LEED points a house has ever received in the U.S., according to Yannell.

“When this occurs, the home will actually be the greenest house certified by the LEED program,” said Yannell. “Achieving net-zero energy status (the home will produce more energy than it consumes) assured that the home would be as energy efficient as possible.

“Many underestimate the availability and practicality of alternative energy systems in home building in colder climates,” added Yannell. “I want to change that attitude and ultimately change some building behaviors. In my mind, LEED Platinum and zero-net go hand in hand, and I will be very excited once we achieve certification and demonstrate 12 months of energy data that proves the house is a net-zero house.”

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