Article No: 126

2006-05-02 13:02:44
LEEDing Yellowstone to a 'greener' future
By: Carole McMichael


 Photo courtesy of Xanterra Parks & Recreation

The natural beauty of Yellowstone National Park makes it the perfect site for building environmentally friendly homes and a perfect fit for the LEED standard of "green" construction. LEED is Leadership in Energy and Environmental Design, a point system developed by the United States Green Building Council (USGBC).

One of the major initiatives of the Yellowstone National Park Service is that its primary concessioner, Xanterra Parks and Resorts, operates in a way that minimizes any possible negative environmental effect from its hotels, lodges and guest activities. Jim Hanna, Xanterra's director of environmental affairs, oversees all efforts to that end — no small task as the park services more than 3 million people a year.

Part of Hanna's job is to help provide housing for the 3,000 Xanterra employees. In October 2003, in partnership with the park service, Xanterra had two single-family homes built by Martel Construction in Gardiner, Mont., a gateway community to the park. The concept guiding this project was to build the greenest and most energy-efficient buildings that they could that would serve as a test case for possible future green building projects within Yellowstone and other national parks.

"Because we want to go in the direction of sustainable building," Hanna said, "this was a great opportunity to build LEED-certified homes from the ground up. LEED was established by the USGBC, which is a consortium of builders, architects, government officials and basically anyone who has an interest or stake in green building concepts. They set up a voluntary building code and provide a checklist of green and innovative conservation concepts."

Construction practices are compared to the LEED checklist, earning a LEED score. The more points you get from the checklist, the higher the certification designation. Starting with "certified," the lowest level, it goes to "silver," "gold" and "platinum." According to Hanna, the green premium is not really that much more expensive than traditional construction considering return on investment; and the payoff on this is really excellent. (See www.usgbc.org for more information.)

Team effort
Besides working with the park service, the preplanning team involved a number of LEED-accredited professionals. Their accreditation is not required for project certification, but Hanna, who is accredited, noted the advantage of working with people who would be familiar with LEED standards of green building, sustainable site design, the point system and the methods for achieving those points. Hanna's team included subcontractors to the architect, such as mechanical, structural, electrical and civil engineers, as well as a LEED consultant.

"We hired on a consultant from the Iowa National Engineering Laboratory to do the energy modeling for both houses," Hanna said. "They looked at the structure, the window placement, the orientation of the home and the construction materials. Then they created a mathematical model to compare with a standard wood-frame home to get a number that indicates how much more efficient the home is going to be. Modeling is nothing new for building design. For every system, such as circulation of fresh air, heating systems and lighting, there is modeling to help determine the best method to use."

Sustainable strategies
The team came up with the following major sustainable strategies: a super-insulated envelope; passive solar heating; a photovoltaic cell system and using regional materials, state-of-the-art mechanical systems, construction-waste recycling and highly efficient plumbing fixtures.

"LEED scores several different categories," Hanna said. "Site selection is one of the major point categories. Components include controlling soil erosion, sediment control during construction, minimizing disturbance of the site, avoiding locations that were formerly farmland, wetlands, ecologically sensitive areas or a flood zone, and selecting locations near alternative transportation routes. You get extra points for using a previous industrial site where your construction actually improves the site. This is what we did. Our site used to be used for fuel transfer, so when we took over the site, it had a lot of abandoned industrial tanks and material, as well as contaminated soil that had to be cleaned up. You also get points for recycling waste at the jobsite and minimizing the amount of dust. We covered dirt piles and used non-potable water to suppress dust.

"The soil is mostly clay, and Gardiner is a pretty arid area. To gain LEED points for building with sustainable landscaping, we chose not to put in an irrigation system, but planted native species and dry-resistant plants. The plants look great but don't take much water. There is a huge waste of water when you use plants that shouldn't grow in this climate."

Energy points
Hanna told the architects (Overland Partners Architects and StudioForma Architects) he wanted the homes to be at least 40 percent more energy-efficient than a standard home. To create a super-insulated envelope, they came up with insulated concrete forms (ICFs) as the building system — specifically, Quad-Lock panels from Quad-Lock Concrete Building Solutions. The architects did some general research on ICFs, then chose Quad-Lock because the forms produce almost no waste, were easy to assemble and didn't present a steep learning curve for a first-time experience — the situation faced by the contractor and crew. They were given three days of hands-on training by a Quad-Lock technical rep and access to onsite help or consultations by phone.

The lot was on a serious slope, so the design for the three-story houses took advantage of the incline, putting the lower level partially below grade. In the foundation and lower level where the builders used Quad-Lock Plus panels, there are 8-inch concrete cores, making the total wall width about 14 inches. The upper floors have 6-inch concrete cores, making the total wall width 12 inches. On the exterior, they used 4-inch foam panels, and on the interior, 2-inch foam panels. The panels interlock with four ties to a unit. The fire-retardant expanded polystyrene (EPS) foam is impervious to moisture, inert, chemically stable and has a zero ozone depletion rating — all good benefits for green building. Also, with these ICFs, they could get a lot more R-value (a choice between 22, 32 or 40) than with wood-frame.

The roof system was constructed of SIP panels rather than a truss system. The advantage was two-fold: they gave much better insulation value than a standard roof truss system and they provided a large interior space that was used for cathedral ceilings on the third floor.

"On the level of the dormers," Hanna said, "we stopped the ICF construction and finished with wood. In those areas, we have blown in cellulose insulation. Because the ICF walls were already 12 inches thick, we were able to put in 12 inches of insulation. We used a netting system as it was blown in to hold it in place and pack it in."

Facing south
"One of the main energy-saving components is passive heating," Hanna said, "using the abundant sun in Gardiner. The houses are facing south. By having a lot of thermal mass from concrete floors, we could use it to keep the houses (4,743-square-footage for both units) cool in summer and warm in winter. Our design focused on letting in as much sunlight as we could. The placement of the windows maximized the number on the south side of the house. We selected window glazing to maximize UV penetration through the windows, as well. On the north side, we had fewer and smaller square footage from windows with standard glazing.

"The goal in the winter, when the sun is low in the sky, is to heat up the concrete floors. On the second level — the main floor — we had a 12-inch concrete slab floor and on the third level, a 6-inch slab floor. The sunrooms also have flat concrete walls facing the sun to absorb passive solar heat. The rest of the walls are actually fully insulated so they are getting their thermal energy through heat transfer from the floor.

"One of the important things with passive solar design is to get it right. If you get it wrong, you will have a sauna in the summer; so the architects designed extended overhangs for the main sunrooms. This means that in the summer during the day, you are getting very little direct sun at all. On the top floor, we have a louvered overhang. In winter with the sun low in the sky, we get direct sunlight. When the temperature is in the low 20s or below zero, the winter sun will heat the rooms comfortably."

If Gardiner gets several days without sun in winter, it will get cold, so the houses do have a backup heating system: a high-efficiency propane boiler that provides hydronic heat through the baseboards for the whole house. There are three heating zones, each piped to a different floor. This makes it easy to change the temperature throughout the day. If passive solar is enough for the main floor, but the basement is too cold, heat can be turned on there but not on the main floor.

More from the sun
The photovoltaic electric system on the rooftop was another material choice that helped meet LEED standards. The system generates about 40 percent of the homes' electricity from the sun. When the sun hits the silicon wafers wired together into photovoltaic panels, they generate an electric current that is fed back into the house to supplement the power from the grid. If at times it generates more power than the house is using, it is fed back to the grid for an energy credit. The meter actually goes backwards. Xanterra got a grant from the electric provider to install a photovoltaic system because, as many providers are realizing, it is cheaper for them to pay for users' systems, which lower demand, than build a new power plant to meet increased demand.

"The electricity generated by photovoltaic cells runs through an inverter right next to the circuit panel," Hanna said. "It comes into it as DC current and is converted to AC. You have two sources coming into the home, one from the power grid and one from the solar panels. The inverter measures the demands of the house and feeds power into the house from the grid or solar panels or both, which is generally the case.

"We didn't have the roof space to provide for the total electrical demand. It covers just the south-facing roof. The key to solar panels is the location and angle at which you place them. The best angle is based on your latitude. The roof pitch was built to match that angle. You can severely decrease your output if the angle is wrong."

LEED verification
To get LEED-certified, the team submitted an application packet to the USGBC. "We document everything we can with photographs, design documents and verification forms from designers and other subcontractors," Hanna said. "For example, to get the landscaping points, we submitted a list that was signed by the landscape architect that verifies that we used native, dry-resistant, non-irrigating plants. For recycling points, you give them the tickets and spec sheets on the materials you used. Indoor air quality is very important to LEED, so you show them that you purchased low-VOC (volatile organic compounds) paints and low-VOC recycled carpet. You also show them the ventilation design and proof of the flushing out of the system.

"The LEED standard is designed for new, remodeled or renovated commercial buildings, and is becoming very popular with that sector. A lot of cities, counties and states are beginning to mandate that all new government or municipal construction be certified. A LEED standard for residential is still in draft form. There are different aspects in residential building; for example, the air exchange is completely different. For the two homes we built, we were allowed to use the commercial standard. The good thing about LEED is that it gives you a comprehensive checklist of options. You get to choose. It is not a rigid standard that tells what you must do. You pick the ones you want to do. If you earn enough points, they will certify your project."

Hanna considers these two houses as test cases. One of the big missions of the park service is education. Generally it is about animals or natural features of the park, but he will be educating visitors about LEED elements of sustainable design. This means setting up tours of the houses for visitors and the nearby Gardiner High School students, whose teachers will incorporate these building concepts in school lesson plans.

For the next couple years, Hanna, who lives in one of the houses, will be in charge of measuring the energy used, the output of the solar system and whether the other energy-efficient strategies are working and keeping the house comfortable.

"We are very excited about this project because it is setting a standard for the park service and Xanterra that I hope becomes the future for all construction in the park," Hanna concluded.