The primary function of this beautiful new home, at 8,500 feet in the Colorado sky, is to serve as an entertainment getaway for family, friends, and business associates of the owners, Dean and Kathy Buysee. The Buysees are successful turkey farmers from Minnesota, who commissioned this home to be built in Woodland Park, CO, overlooking Pike’s Peak, one of the most celebrated of U.S. landmarks.

The Buysees had installed a geothermal system in a farm shop business, and were familiar with geothermal’s capabilities and benefits. Fortunately, as they scouted for a Colorado-based contractor, they became acquainted with someone with a grasp of geothermal concepts, and an understanding of how to leverage them for absolute efficiency: Al Wallace, president and principal owner of Energy Environmental Corporation (EEC) of nearby Centennial, CO.

Wallace and EEC had been designing and installing high-performance, integrated HVAC and renewable energy systems for 10 years, for projects of many sizes. From stand-alone ground source heat pumps to fully integrated hydronic and air systems with BACnet controls, EEC has been there, done that. Al Wallace knew what the Buysees wanted, and he knew how to make it a reality.

“We toured EEC on an extremely hot day, and it was the type of cool, air conditioned comfort we wanted, without any air movement,” Dean Buysee recalls. Kathy Buysee also appreciates the elimination of dust in the air, for a home that’s easy to keep clean.

Comfortable, Efficient, Durable
At an altitude of 8,500 feet in a dry climate, there was concern over maintaining a comfortable level of indoor humidity. In addition, without access to natural gas and rising propane costs, the homeowners wanted high energy efficiency to reduce utility costs. Durability was a concern as this home was intended for occupancy on an irregular basis, and subject to severe weather.

While the Buysees didn’t desire Leadership in Energy & Environmental Design (LEED) or Energy Star certification for the home, EEC consulted with the owners and their designer — Jerrod Nelson, Nelson Design Service — to implement elements of both LEED and Energy Star. Of first priority was a tight, well insulated, high mass building envelope incorporating energy recovery ventilation. The home is built using an insulated concrete form (ICF) structure, for superior energy efficiency.

“Dean Buysee was very conscientious about having a tight building envelope, and it’s performing better than off-the-shelf homes,” explains Wallace. “The home has 10-in. walls on the first floor, and 8-in. walls on the second, for an oversized thermal mass. We’ve been able to take advantage of the improved building envelope to lower compressor speed, which provides higher efficiency operation.”

The integrated systems design provides heating and cooling through a 120/MBTUH ground source heat pump with reversing valves to provide hot or chilled water to dedicated heating and cooling buffer tanks. Water is distributed through half-inch diameter Uponor AquaPEX-A hydronic distribution piping at six inches on-center, a critical measurement.

“With radiant floor cooling you have to put the tubing six inches on center, which is a higher density than any heating recommendation you’d ever find elsewhere,” says Wallace. “By installing the tubing six-inches on center, it allows you to deliver as much heat as you need to any zone. So if you have a small bathroom, with tubing six inches on center, you’re able to provide any heat response to the room that’s required. Once we designed the system for radiant floor cooling, we didn’t worry about the spacing of tubing in heating mode because we knew we had far more capacity than we needed. We only had to determine the flow rates for each zone and sizing our supply and return manifolds to support that.

“Larger piping also makes the system more efficient, because the pump pressures are a lot lower when you’re circulating the supply and return,” Wallace says.

The home’s geothermal heat pump (GHP) has the capacity to heat domestic hot water (DHW) through a heat exchanger. A wine cellar is cooled via radiant floor cooling and a chilled water hydronic fan coil.

Precise Radiant Zone Control
The home’s BACnet control system used commercial off-the-shelf control modules from an Uponor Climate Control System. Additional BACnet programming was required to support the radiant floor cooling.

The home was divided into 19 individually-operated radiant zones. Five snowmelt zones, including the garage zones, operate separately, and are freeze protected with propylene glycol.

All bathrooms are zoned separately from adjacent living spaces. Bathrooms are enabled for heating only (no cooling), due to the possibility of condensation when cooling, from the rapid rise in humidity from showers.

The Buysee’s desire to have remote access was especially challenging.

“In that regard, you have to look at the systems from the point of view of what will happen should one system fail and another system has to pick up the load,” Wallace explains. “You have to consider multiple ‘layers’ of comfort but also layers of reliability. The biggest challenge for us was designing the system so you had automatic roll over. Because, if the system froze up, there could be severe issues. If the heat pump fails, the boiler has to kick on. If the boiler fails the electric heating element has to kick on. We fused those elements together and staged them to activate in the right order, based on energy efficiency. The geothermal ground loop consisted of 3,600 ft. of piping in solid granite, “which provides the best thermal connectivity you can get,” Wallace says. Six wells were drilled, 300 ft. below the surface.

Control Benefits of Radiant Systems
EEC’s design eliminates many of the inherent balancing and comfort issues prevalent in air systems, such as hot and cold spots, and zoning control. Wallace truly appreciates radiant’s simplistic efficiency.

“It’s hard to get an air molecule to go where you want it to go, or to get the right volume of air to go off of a branch duct. A radiant system doesn’t require any of that math. It’s a pipe that carries water. Hot is left, cold is right. Because of the type of hydronic technology that’s available today, we can deliver energy to a zone or room much more easily,” Wallace says.

Each zone contains an Uponor Climate Control Network (CCN)-compatible thermostat. The thermostat has an air temperature sensor, an infrared floor temperature sensor, connections for an in-slab temperature sensor and a humidity sensor. These intelligent devices communicate with the CCN control system to determine radiant supply temperatures to the home. In heating mode, the supply temperature uses outdoor reset control to maintain the lowest temperature required to meet heating demand. The GHP maintains the heating buffer tank at this temperature. With PEX-A tubing installed at six inches on-center to accommodate RFC, the system operates at a lower operating temperature than when tubing is installed more typically at 8- or 12-in. on-center. The extra capacity provides some insurance to the contractor when two zones have different entering water temperature requirements.

In cooling mode, the CCN calculates dew point and sets the cold tank temperature below dew point, to provide chilled water to fan coils in-line with the ERVs. At the same time, a three-way thermostatic mixing valve provides the supply temperature to the radiant manifolds at an offset temperature above the dew point (usually 4- to 5-degrees) to prevent condensation in the floors. When outside humidity is below 50% (the normal Colorado climate), the ERVs operate without the chilled water fan coils in operation. However, when outside humidity increases substantially (as will happen during summer thunderstorms), the chilled water is circulated in the fan coils to dehumidify the indoor air below 50% so that the radiant floor system maintains its effectiveness.

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Unlike an air system, the hydronic system as designed by EEC is almost self-balancing. Each zone has a dedicated multi-temperature sensor, and individual control with a dedicated zone valve, making every room a micro-climate in the overall heating and cooling envelope.

Commissioning involves confirming that the zone valves are responding to the control inputs, and overall system set points for the hot and cold buffer tanks, and DHW tank, are maintained by the geothermal heat pump. When the GHP is turned off, boiler operation is confirmed to meet heating set point in the hot buffer and DHW tanks. When the GHP and boilers are manually de-activated, the electrical heating elements in the DHW tanks are tested to maintain the minimum set point manually established on each tank.

Commissioning Challenge With ICF Design
A challenge was found in modeling and performing Manual J calculations on the true thermal envelope with the ICF structure. On several retrofit applications involving ICF homes, EEC has found that the building envelope didn’t perform to the ICF manufacturer R-value claims. According to Wallace, there’s an “art” to working with the science of ICF high mass systems.

EEC performed Manual J calculations using RightSuite universal 8.0.18 software based on the ICF manufacturer’s specifications. Incorporating a DHW demand of 20 MBTUH (as calculated by Water Furnace GeoLink software), the GHP sizing was 120 MBTUH, using a 100% runtime at 0F outside air design temp. The Uponor Manual J calculations were 165 MBTUH total radiant heating load, an increase of 65%. Since backup boiler capacity was available, the GHP was sized based on 120 MBTUH. This is an acceptable value-engineering approach in heating dominated climates. Reducing the size of the GHP system reduces overall system first costs by reducing the ground heat exchanger (GHEX) “ground loop” expense.

Worry-free, Comfort-filled Escape Zone
Dean Buysee says the home’s comfort system is performing better than he anticipated it would.

“It’s performing well below where I expected it to be for energy consumption,” he says. “It’s already paying back in energy savings.”

Additionally, the system’s comfort benefits are a pleasant reminder of the Buysee’s wise decision to go with a geothermal system installed by Energy Environmental Corporation.

And when you travel 1,000 miles to enjoy your Colorado getaway, that’s what you want to take back home with you: sweet memories of cozy comfort.

PRODUCTS KEY TO SUCCESS

  • Uponor Climate Control Network (CCN)
  • Enertech GeoComfort Comfort Series heat pump
  • Grundfos pumps
  • Triangle Tube Prestige condensing boilers
  • Ultimate Aire 200DX energy recovery ventilator
  • Ultimate Aire water-to-air coil
  • Enertech Hydronic fan coil
  • Wilo Stratus VFD circulators
  • Grundfos circulators with Webstone flanges
  • Rheem Marathon hot water tank
  • Lochinvar Squire storage tank
  • Flat Plate heat exchanger
  • Triangle Tube MaxiFlo heat exchanger
  • Spirotherm air eliminators