Energy efficiency was central to the design work done by the architectural students from the University of Nebraska and University of Arizona in Boone County. Energy costs have already risen to a point where older (and often historically significant) buildings can be too expensive to heat and cool, and energy costs will only continue to increase. Using the earth for thermal insulation and the sun for heat were among the ways students made their designs as sustainable as possible. But since these techniques require a building be oriented towards the sun and/or be partially buried in the ground, they are often only applicable to new construction.
Adaptive Reuse and Repurposing
Omaha architect Steve Eveans, with 30 years experience redeveloping rural communities and urban neighborhoods, is an expert in improving the energy efficiency in older buildings. According to Eveans, “the most energy-saving and pollution-reducing activity is the preservation, adaptive reuse and repurposing of our existing built environment. Fully 95% of the energy used in a structure’s lifetime is expended in the manufacture of the building materials and in the construction process. Only 5% over the lifetime of the building is expended on operation and maintenance. Energy retrofits and upgrades need to be considered among the top three best investments you could make in your property for all kinds of sustainability and stewardship reasons.”
Eveans, whose experience includes developing the redevelopment design standards for the former Martin Bomber Plant in Bellevue – a project with “extreme issues with HVAC, roof insulation, and window systems” – has found there are effective conventional ways to improve an existing building’s energy efficiency. Eveans recommends the following techniques to save the most energy in the most cost effective manner:
- Natural day lighting
- Good thermally efficient operable windows
- Good sealants
- Appropriately placed and sized insulation using attic ventilation
- Light colored roofing materials (recycled TPOs)
- Conventional moderately high efficiency equipment using natural gas for heat
Some existing buildings can be modified to harness the sun’s energy. While photovoltaic solar panels are still too expensive for practical use, their prices are falling. Passive solar heating, meanwhile, can be utilized in existing masonry buildings if they have sufficient exposure to the sun. Using a technique known as a trombe wall, the brick or stone façade of an existing building can be used to store the sun’s heat during the day for release at night.
Though patented in 1881, the trombe wall has only recently gained popularity for its passive solar properties. It consists of an external layer of insulative glass positioned a few inches in front of a sun-facing masonry wall. Since the masonry is slow to cool down at night, this allows storing the sun’s heat for later use. Vents at the top and bottom of this wall allow heated air in the space between the glass and the masonry to circulate through the building at night.
Trombe walls often incorporate slats or an overhang positioned to block the sun in the summer while still allowing it to reach the masonry in the winter. In some instances, though, a trombe wall is used in the summer as a solar chimney. Heated air between the glass and the masonry is vented outside, drawing cooler air into the building even if no wind is blowing.
A trombe wall can be retrofitted to an existing masonry building. And by adding colored lights behind the glass, a trombe wall can create a striking nighttime visual effect, drawing people to the area.
A valuable partner to those considering preserving/repurposing an older building — especially a building with historical significance — is Heritage Nebraska, “a statewide non-profit organization celebrating history through advocacy, education, outreach, preservation and stewardship.“
According to its director, Elizabeth Chase, Heritage Nebraska is a “citizen’s organization that works with any and all individuals, communities, projects, and organizations to preserve our architectural heritage in order to build stronger communities and maintain the essential character of the state. Heritage Nebraska educates and engages community leaders regarding the economic benefits and importance of preservation; trains volunteers, business leaders and property owners in established best practices; provides vision to help communities identify their assets and help to find the resources needed to make great things happen; links communities and individuals to the nationwide network and resources of the National Trust for Historic Preservation.”