News

Out with the old… in with the new

May 21, 2011

This spring and summer, the Great Lakes Campus will receive some much-needed improvements to add longevity to Earth Hall and the Environmental Learning Center (ELC). For many on campus, these two buildings are emblematic: Earth Hall, the grass-covered academic and administrative building hiding on a hill, peering down over Louie’s Pond, and the Environmental Learning Center, easily melting into the forested landscape. Each has an architectural history interwoven with cutting edge practices in environmental stewardship and the birth of Au Sable Institute.  With these new repairs, we decided to look back on the story of how these buildings began and offer an inside look at how they function.

Earth Sheltered, Earth Hall

When Au Sable Trails Junior Science Camp became Au Sable Institute in 1979, it was obvious that the camp buildings would not be adequate for the new institute. Consequently, staff began conversations about a new building to house offices and classrooms. The existing camp buildings were designed to blend into the landscape, but given the square footage requirements of the new building, it became apparent that a traditional building would overwhelm the landscape. Someone suggested that the building be pushed into the ground, and thus the idea of an earth sheltered building was born. Earth sheltered building was a new practice in northern Michigan in 1980, but staff found a Traverse City architect who was working in this field, and who was intrigued by our proposal; and so Earth Hall was born.

How It Works

Engineering the roof is always the most challenging aspect of an earth sheltered building. It requires multiple layers to support weight and drain rainwater. The architect’s approach was to use pre-stressed concrete beams 18 inches wide and 12 inches thick. The undersides of these beams serve as the ceiling of Earth Hall. A concrete slab that is four inches thick along the outside edge and tapers to two inches in the center of the roof holds the beams together. There is also a 12 inch curb around the outside edge of the slab creating, in effect, a wading pool. A bituthene membrane to seal out water lines this pool, and a perforated drain pipe runs down the center of the roof along the long axis of the building from south to north where a drain hole was cut through the curb for water to exit. Four inches of Styrofoam sheeting lay on top of the membrane and sewer gravel covers the drain pipe. Fourteen inches of earth, seeded with rye grass, top everything.

These extra rooftop layers, coupled with the soil built up around the sides of Earth Hall, provide extra insulation, and the plants supply food and habitat for local wildlife.

Repair Work

The system worked well for 27 years until leaks formed through the ceiling into the main floor of Earth Hall. While the leaks were repaired, they became more frequent until one hard rain storm last fall produced leaks at 7 different spots along the perimeter of the roof. The roofing company who has done Earth Hall’s repair work reported that the bituthene membrane used to seal the roof has a life expectancy of 20 years, meaning our Earth Hall has out-lived repairs by 7 years. Thus the challenge for the summer of 2011: Remove 14 inches of earth, 4 inches of Styrofoam, a drainage system and a membrane and replace it all with a new green roof.
 

ELC Ground Water Heating System

The Environmental Learning Center was built as a summer-only classroom/lab in the mid 1960’s, but it became the home to the Environmental Education Program when it began in 1977. Wall-mounted, propane furnaces stood in each room to provide the heat required for a year-round program. These furnaces were inefficient, drafty, noisy and smelly, so in 1992 staff decided to replace them with in-floor, radiant heat provided by a geothermal system. It was a wonderful solution to the deficiencies of the old, wall-mounted furnaces. Students loved to sit on a warm floor, and the instructors did not have to shout over the furnace blowers.

How It Works

Geothermal heating uses the earth's warmth and a heat pump to heat water that is propelled through a series of pipes in the ELC floor.  It is a closed loop system in which the water is stored in a holding tank until thermostats in the rooms call for heat, and the cycle commences. The ground water heat pump that makes the process work is basically a large refrigerator. A refrigerant (freon is no longer used), in gaseous form is pumped through a compressor to a pressure of 250 psi. This heats the gas to 128˚ F. This hot, pressurized gas passes through a heat exchanger (think a car radiator) where the heat is transferred to a solution of water mixed with RV antifreeze. This warm water is then pumped through ½ inch diameter tubing imbedded in the concrete floor, heating the room.  

After the pressurized gas has passed through the heat exchanger with the water/antifreeze solution, it loses most of its heat. It then passes through a pressure relief valve that drops the pressure to 60 psi which condenses the gas to a liquid refrigerant and lowers its temperature to 35˚ F (remember high school Physics). The liquid refrigerant descends through piping into the ground where it passes through another heat exchanger and absorbs heat from well water. The well water is 50˚ F, but that is hot enough to boil the refrigerant back into a gas and the cycle is repeated. The well water has been cooled to 45˚ F and is pumped back into the ground to regain heat. In this way, the system is more energy efficient than regular heating, since it relies on the heat stored in soil and water underground (in this case, in ground water) to help heat the building.  It also creates a more comfortable, less noisy solution to heating public spaces.

Repair Work

The system was installed in 1992 and was a first generation system, one of the earliest of its kind, designed and built locally. After 18 years the tubing in the heat exchanger had deteriorated to the point that it was leaking and could not maintain pressure. We replaced the heat exchanger this past April to keep using the Earth’s warmth to heat the ELC.