“If you want the most comfortable and efficient home possible, you have to start by studying our planetary home, the Earth,” he said. “How is the Earth heated and cooled? Next study how the human body gains and loses heat. It’s surprising how simple and elegant an HVAC system can be when we copy the master.”

Sustainable Installation

After learning about energy efficiency incentives through New York State Energy Research and Development Authority’s (NYSERDA) Energy Star Labeled Homes program, Rowe approached Norwalk, Conn.-based Steven Winter Associates Inc. (SWA) for guidance.

SWA officials determined his home improvement goals aligned with the LEED for Homes program through material and resource efficiency, sustainable sites, water efficiency, and IAQ.

Integral to sustainable design, the home’s efficient thermal envelope includes R26 insulated concrete forms (ICFs) below grade on an R10 slab. R26 ICFs continue above grade to the framed R54 roof sprayed with 3 inches of closed cell and 6 inches of open cell insulation. A thermal imager was used to verify insulation, and to identify weaknesses in the envelope for repair.

The home’s efficiency is furthered through water-to-water GeoComfort ground-source heat pumps by Enertech Manufacturing for radiant floor heating and an Uponor radiant cooling system. The heat pumps are fitted with a desuperheater, which reclaims energy for domestic hot water storage and dehumidification reheat.

A RenewAire EV450IN ERV provides whole-house ventilation and central bathroom exhaust. A Unico System M Series high-velocity air-handling unit maintains whole-house humidity control through a MERV 10 filter, ECM motor, chilled water coil, heating coil in reheat position, and connected Nortec humidifier.

Triangle Tube’s 95 percent efficient condensing boiler is included as a heating backup with domestic hot-water production provided by Triangle Tube’s smart indirect-fired water heater. The domestic well utilizes an energy-efficient and constant-pressure variable-speed submersible pump made by Grundfos. The water and geothermal vertical wells were drilled by Boyd Artesian Well Co. of Carmel, N.Y. A low-emitting Renaissance Rumford wood-burning fireplace features a fully sealed, gasketed door and ducted combustion air.

Energy-Efficient Operation

To optimize energy efficiency, the hydronic circulators used in conjunction with the ground-source heat pumps provide heating and cooling by pulse width modulation duty cycle and variable speed control. The first four circulators are 15-58FC zone pumps, operating on medium speed at 60-80 W with a 50 percent duty cycle for December through February, and July through August; and a 25 percent duty cycle for other months. The next circulator is also a 15-58FC pump that is controlled as a variable-speed injection pump operating at a 20-60 W maximum. Another circulator is boiler heat backup, 15-58FC, on medium speed at 80 W, only running about 20 percent duty cycle January through February. A final pump, 26-99FC, operates on medium speed 179 W and is for direct-coupled ground-source radiant cooling only operating in the summer at 50 percent duty cycle. This combination heat pump flow control uses about 480 W to heat and cool the structure.

Rowe’s home also features in-floor radiant heating and cooling. The system is embedded in concrete for each floor, as the basement is slab on grade, and the second and third floors are poured concrete over ICF decking. The concrete thermal mass construction acts as a thermal energy flywheel to offset overnight peak loads, so the mass stores energy and regulates temperature fluctuations.

“Bill Cotton, of Cotton’s Concrete in Athens, Pennsylvania, and his team had to work very closely with Aaron on the installation of the tubing into the LiteDeck floor slabs,” said Rowe. “It was a pleasure working with some great contractors who I knew I could trust, and they did not let me down.”

The home’s swimming pool is also a key component, acting as another geothermal heating/cooling source. When the heat pump is operating for air conditioning, and the pool is in heating mode, controls divert the energy normally transferred from the home to the Earth, instead from the home to the pool. Geothermal heat exchange efficiency is somewhat less going to 80˚F pool water rather than 55˚F ground; however, the compromise is beneficial as the pool heating becomes a byproduct of air conditioning. When the pool heat is off, controls divert back to using the vertical ground loops as needed for air conditioning. This design required a properly sized close approach flat plate heat exchanger made of titanium to endure the saltwater pool treatment system.

For radiant cooling, the ground-source heat pump system reverses from heating mode to cooling, charging the 120-gallon buffer tank with chilled water instead of hot water. A variable-speed mixing pump controls the water temperature from the buffer tank to the radiant floor cooling system.

The ERV provides 253 cfm intermittently (11 hours/day) to meet ASHRAE Standard 62.2. With sensible recovery efficiency of 67 percent and total-recovery efficiency of 46 percent, the energy recovery ventilator is in line with most equipment efficiencies, but uses a significant 490 W during run time; fortunately, it also doubles as a bathroom local exhaust.

The home is monitored and controlled via an Automated Logic building automation system, which can access all 16 zones through remote sensors that are Internet accessible.

“Aaron has a rare passion for technology and all things involving HVAC,” said Rowe. “He guided me through our joint vision for a highly energy-efficient house comprising a geothermal energy source, radiant heating and cooling, insulating spray foam, and web-enabled monitoring and control systems. I had to trust him, and it paid off.”

Publication date: 05/14/2012