The REHAU MONTANA ecosmart house is a living laboratory for green heating and cooling technologies.

Cal Sampson (left) and Tyler Sampson of Bridger Drilling install prefabbed REHAU Helix probes in 20-foot-deep wells, in addition to the four 300-foot-deep wells for conventional geothermal piping. (Photo credit: REHAU Construction.)


One of the drawbacks of trying to sell homeowners on the advantages of installing an energy-efficient heating system using radiant, geothermal or solar thermal technologies is the lack of real numbers to back up performance claims. Most energy performance numbers are based on computer modeling of how building occupants will use the systems.

Those numbers rarely come close to how human beings actually use their heating and cooling systems.

Researchers at Montana State University in Bozeman, along with sponsor REHAU, are about to change that perception. The REHAU MONTANA ecosmart house, currently under construction in Bozeman, will feature the latest sustainable building products and systems. This living laboratory will study over a four-year period how these various building systems can best be integrated for optimal energy consumption, comfort and life-cycle costs.

The 3,800-square-foot, three-bedroom home is the brainchild of Bill Hoy, director of strategic building development at REHAU. Hoy, an architecture graduate of Montana State, helped start the MSU College of Arts and Architecture’s Creative Research Lab (www.montana.edu/crlab), which is overseeing the project. Hoy and his family will move into the home after the initial two-year research period. The home is expected to be completed later this year.

Hoy had purchased the land before he went to work for REHAU. In 2008, he approached Terry Beaubois, director of the CRLab and ecosmart project manager, with the  concept of building a house to research and identify the most cost-effective, energy-efficient heating and cooling systems, yet still provide a high level of comfort for residents. Beaubois was intrigued with the idea.

When the time came to obtain a corporate sponsor for the project, they met with Dr. Kitty Saylor, CEO of REHAU North America, about installing the company’s energy-efficient products in the home. Saylor agreed and, in return, REHAU was given naming rights for the house.

In 2009, Hoy was laid off from Washington, D.C., real estate firm B.F. Saul Co., where he was senior vice president of construction. During the Bozeman project meeting with Saylor, she offered Hoy a job. He started at REHAU in August 2010 and moved his family to Montana.

During the first two years, CRLab researchers will study the different heating and cooling systems in the unoccupied home. They will also compare international sustainable building standards with their residential model, thus helping determine the best approach for homeowners to attain certification for LEED For Homes, Energy Star homes and National Association of Home Builders’ National Green Building Standard.

Once the homeowners move in, another two years of research will examine how the family is interacting with the heating and cooling systems and compare those findings with the energy-usage performance model. The CRLab will submit a post-occupancy evaluation and real-time data results will be published on the home’s website - www.montanaecosmart.com.

Excess solar energy will be redirected to a heat sink buried 10 feet under the front patio concrete slab during the summer. The heat sink - four zones of 1-inch PEX looped in 400-foot runs over sheet foil insulation - was designed by Patrick McMullen of PJ’s Plumbing and Heating. (Photo credit: PJ's Plumbing & Heating.)

Sustainable Smorgasbord

As the primary sponsor of the ecosmart house, REHAU is providing many of the sustainable heating and cooling systems’ components:

  • Geothermal ground loop heat exchange. RAUGEO PEXa pipe is installed in four 300-foot-deep vertical wells with 1-inch-diameter double U-bend in each for optimal energy extraction. Ground loops are connected to a combination heat pump (water-to-water and water-to-air) to handle the radiant floor heating system and the forced-air ventilation system.

    In addition, prefabbed Helix probe prototypes (130 feet of 1-inch PEXa pipe configured in a 15-inch-diameter spiral) were installed in shallow, 20-foot wells to see if this type of system would be feasible in areas where deep wells are not practical, Hoy explains.

  • Ground-air heat exchange. The ECOAIR system is the primary supplier of fresh air to the home. Outdoor air is pulled into a 6-foot, stainless-steel inlet tower - outfitted with an electrostatic/HEPA filter - then pulled underground, around the perimeter of the house, through 8-inch ECOAIR PVC pipes with a silver-lined antimicrobial layer. Air is ducted throughout various zones in the house.

    Ecosmart has two duplicate systems to compare performance. One system is installed 7-feet deep outside and the other 6 feet below the basement’s concrete slab.

  • Radiant heating and cooling. This system circulates heat transfer fluid through 1/2-inch RAUPEX PEXa tubing embedded in concrete in the basement and suspended wood floors. Tubing is connected to the geothermal system to provide warm or chilled water.

    The RAUPEX tubing is tied to mesh on 6-, 9- and 12-inch centers on the lower-level slab, and rebar on 8- and 12-inch centers on the upper level, says Patrick McMullen, owner of Belgrade, Mont.-based PJ’s Plumbing and Heating, the installer for the radiant heat, snow melt and solar thermal systems. Tubing is connected to REHAU PRO-BALANCE manifolds. Each floor took the three-man crew from PJ’s one day each to install about 5,000 lineal feet of 1/2-inch radiant tubing.

    In addition, REHAU radiant cooling panels are used to lower the surrounding air temperature.

  • Snow and ice melting. REHAU’s snow- and ice-melting system is installed in a section of the driveway and the front porch and heated by the geothermal system. It is sized to minimize the safety hazards of icing and modest snowfall to conserve energy. About 900 lineal feet of tubing for 600 square feet is used for this system, McMullen says.

  • Solar thermal system. Domestic hot water and supplemental radiant heat are provided by three REHAU solar thermal panels. The roof collectors are connected to a solar storage tank by way of a pressurized glycol-filled loop. The heat exchanger circulates domestic cold water through the storage tank before supplying the water heater. Excess solar energy will be redirected to the snow-melt system in the winter or a heat sink buried 10 feet under the front patio concrete slab during the summer.


  • The heat sink - four zones of 1-inch PEX looped in 400-foot runs over sheet foil insulation - was designed by McMullen, who first heard about the project from one of his wholesale distributors, Keller Supply.

    “I was at a geothermal training class in Seattle and became interested in the project,” he recalls. “I put my name in the hat and met Bill Johansen from REHAU and the folks at MSU. They invited me to look at the project.”

    Other sustainable technologies that contribute to the building envelope’s energy efficiency are: AAON heating and air-conditioning equipment, which operates the geothermal, heating and cooling systems of the house; Amvic insulating concrete forms (each block used in the ecosmart house consists of 60 percent recycled materials); prefabbed structural insulated panels by Big Sky Insulations; and thermal efficient and durable REHAU vinyl windows and doors.

    Easy-to-use Web-based REHAU smart controls will allow researchers, and later the Hoys, to manage the heating and cooling systems to achieve comfort while using the lowest amount of energy, as well as monitor systems for functionality. Interfacing with weather services allows the controls system to automatically adjust settings before the weather changes.

    The mechanical room houses the Triangle Tube gas boiler and storage tank, and Grundfos pumps and fans. A REHAU FIREPEX stand-alone residential fire protection system is installed throughout the home with concealed sprinkler heads.

    The 3,800-square-foot, three-bedroom REHAU MONTANA ecosmart house includes a smorgasbordof sustainable construction features, such as geothermal heating and cooling, radiant heating andcooling, snow melting, solar hot water heating, and water-to-air heat pumps. (Photo credit: REHAU Construction.)

    Monitoring And Measuring

    Students in MSU’s mechanical engineering department placed more than 350 sensors throughout the ecosmart house and with its underground systems to record temperature and energy data, says Kevin Amende, adjunct assistant professor in mechanical engineering technology at Montana State. Amende oversees an HVAC testing facility at the university, which is how he came to Beaubois’ attention.

    “The sensors will help determine how each individual component in the house is performing,” Amende states. “We’ll also be running tests to see how one system performs against another - radiant, forced air, heat recovery ventilation system and ground-air heat exchange.”

    Energy data will be recorded and analyzed to verify each system as a residential sustainable technology.

    Amende has assigned students to ecosmart for the last two years. In the preliminary design phase, mechanical engineering students came up with alternatives for cost-analysis of construction materials and their thermal performance. Some students were involved in the energy performance modeling program. That information was passed on to business students on the project; they crunched the numbers and determined the point where it was not economical to add more energy-reducing systems to a structure.

    Most recently, a group of students helped to  create a software program to measure temperature, flow rates and other data in order to give an accurate picture of the home’s energy usage. At the end of the research period, information is to be gathered and disseminated to the heating and cooling industry, as well as the general public.

    “We want this house to be a learning tool,” Hoy says. “We want to extrapolate this data and scale it down for affordable housing. For a 1,200-square-foot home, which system will give homeowners the best return on their investment?”

    Amende adds, “We’re researching which systems are more optimal in different seasons.”

    PJ's Plumbing and Heating radiant installers Eric Chidester (left) and Tim Rogers install some of the 5,000 lineal feet of 1/2-inch radiant tubing in the ecosmart house. An additional 900 lineal feet of tubing is instaled for the snow-melt system. (Photo credit: Meg McWhinney/MSU-CRLab.)

    Interdisciplinary Collaboration

    For Beaubois, ecosmart is more than just learning about sustainable construction. It’s about colloboration and working together successfully within the team - a lesson he hopes his students learn.

    MSU business, engineering and architectural students worked together not only to design systems but to determine real life-cycle costs. The various contractors, REHAU representatives and the owner were all involved early on, which streamlined workflow and avoided misunderstandings. Structural engineering firm Nishkian Monks, general contractor Tollefson Builders and Energy 1 (which provided the drawings) completed the team.

    “Having that early input from everyone allowed us to shape the project,” Beaubois notes. “I want students to realize this type of collaboration is what makes successful projects in the real world. It doesn’t make it easier, but it does make the project better.”

    Amende and Beaubois intend to take the research results from ecosmart and turn them into curriculum for their students.

    “We’re going to create some building industry case studies,” Beaubois explains. “We need to be as transparent as possible. We may consider four or five technologies and select one, but we won’t say that is the one others should select. We’ll explain why we picked that technology and why we didn’t pick the others. They may be in an area where the temperature and humidity is different, and so the conclusion they reach may be different.

    “A researcher’s report isn’t about anticipating a result and reporting that conclusion. We’re not trying to predict the outcome.”

    REHAU and the MSU Creative Research Lab held an open house in mid-August at the ecosmart site.  Construction on the home is expected to be completed later this year. Pictured are future occupants Wanda Hoy (right) and Jenny Hoy, who helped the lab with the 'human sustainable' design aspects of the home. (Photo credit: David Hoy/MSU-CRLab.)

    'Human Sustainability'

    In addition to addressing sustainability issues, the home is designed to accommodate Hoy’s daughter, Jenny Hoy, who is in a wheelchair. There is a separate area in the home for her, complete with kitchen. Beaubois hired her for two weeks to research disability design in the house. She found potential obstacles that someone not in a wheelchair wouldn’t have considered and came up with creative solutions.

    “It’s not just about the sustainability of the materials,” Beaubois notes. “We need to look at human sustainability as part of the (overall) sustainability when we’re looking at materials. It’s not a separate thing; you need to take the people into consideration right away.”

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