There is a growing trend toward using geothermal systems for temperature control in historic structures. Underground pipes that lead to and from the building transmit the earth's heat to the building in the wintertime, and draw heat away from the building in the summer. Geothermal systems are much more efficient than traditional heating and cooling units, and eliminate the need for unsightly equipment like window air conditioners, chillers, and radiators.
From a reactivated cistern to a modern rain garden, the options for conserving potable water and keeping stormwater from running off site at a historic property are manifold. A wide range of water-efficient devices and products is now available, from low-flow kitchen and bathroom fixtures, to rain sensors that control the amount of water sprinkled on lawns. Even better, replacing lawns with drought-resistant plants or recyclable turf can cut down or eliminate the need for irrigation.
Harnessing the sun's rays is proving to be a workable technology for powering many historic buildings, as well as for providing hot water. Solar power use markedly cuts down on electricity from other nonsustainable sources such as coal and oil. If unobtrusively placed, solar panels can blend in with the rest of the building. For example, panels can be placed flat on a roof or at such an angle that they are barely visible.
Besides avoiding the wasted energy inherent in tearing down a historic building, making use of original bricks, terrazzo, and other materials preserves both dollars and aesthetics. It is now standard practice to use materials like wheatboard and reusable carpet in walls, flooring, and furniture. Indoor air quality is factored into the design, especially where buildings have been made more airtight by added layers of insulation. For this reason, non-toxic paints and glues are favored over those that “off-gas” into interior spaces.
Geothermal, solar, and other big-ticket technologies are not the only means of combating inefficiency in an older structure. Enhancing existing elements like skylights is one relatively easy way of keeping lighting and heating costs to a minimum. Strategically placed insulation and the replacement of old warhorse boilers and appliances with high-efficiency equipment considerably reduces costs as well. Daylight sensors and occupancy sensors further cut down on electricity use.
A green or vegetative roof, usually consisting of a garden overlying a layer of waterproofing, can be installed so as not to detract from a building’s historic character. Green roofs collect storm water, serve as a cooling mechanism, and, in some cases, act as an acoustical damper. Another low-impact method involves coating a roof with white or light-colored reflective material. This not only extends the roof’s service life but significantly reduces its heat load by reflecting back most of the sun’s rays.