While the urban environment provides efficient use of space by virtue of its dense human population, the intense concentration of energy consumption and waste streams can strain urban infrastructure. A lot of discussion about improving energy use focuses on transportation solutions, but commercial and residential building development represent even greater opportunities to impact energy use. Construction and building use account for an estimated 72 percent of electricity consumption in the United States [Source: US Energy Information Administration]. A future phase of 18Broadway could explore housing development that is resourceful in construction, modest in energy use and environmentally appropriate to the site itself. The goal is to drastically reduce operating costs while providing a healthy and energy-efficient home environment for occupants.
Net-zero average annual energy use can be accomplished with on-site energy generation. As energy is generated, a second electric meter can record the energy being pushed back onto the electricity grid. When annual grid energy used equals energy pushed onto the grid, a net-zero performance is reached. On-site renewable energy system options include: photovoltaic arrays, which directly convert sunlight to electricity; solar thermal systems, which preheat domestic water; and wind turbines, which convert mechanical energy to electricity. Even if not installed on day one, the building can be “future-proofed” to accommodate future energy generation systems.
Passive systems are energy-reducing building elements that don’t require mechanical means to implement. These systems include, but are certainly not limited to, natural ventilation, solar heating of air and water, high-efficiency envelopes and green roofs. Often a minimal investment can provide huge benefits. By designing just with the sun in mind, it is possible to reduce heating and cooling loads by from 10 to even 40 percent. (Source: City of San Jose, California)
Active building systems use efficient mechanical methods to reduce, and potentially replace, energy consumption. These systems can include: smart utility grids; motion-activated and daylight-sensing light fixtures; tankless water heating; gray water (redirected sanitary water) systems; geothermal ground-loop heat exchangers; wind turbines; and photovoltaic solar arrays. While a geothermal ground-source heat pump runs on electricity, it nonetheless allows you to receive $2.50-$3 worth of heating/cooling for every dollar you spend. [Source: Citizens Electric Corporation, A Touchstone Energy Cooperative, August 2009]
“Smart building” controls provide instantaneous detailed feedback on energy performance to the building’s energy systems and its occupants. Studies show energy use goes down by 15 to 20 percent when occupants have real-time feedback on energy use. [Source: “The Effectiveness of Feedback on Energy Consumption,” Sarah Darby, University of Oxford Environmental Change Institute, 2006] Several super-efficient heating and air-conditioning systems can be demonstrated in this project and their performance can be tracked. All this can be analyzed to establish their real-world viability as financial investments. Fresh air delivery/energy recovery systems and the use of finish materials that do not off-gas toxic chemicals can also provide a healthier and more comfortable environment for people.
Green roofs come in all sizes and provide several benefits. Some are thin, low weight, low maintenance and do not support foot traffic. Others can be great places for people and provide for a wide variety of plants and surfaces. Green roofs retain 64 to 95 percent of average rainfall; protect and prolong the life of the roof membrane; reduce energy loads by insulating the roof and through the cooling effect of the transpiration of the rooftop plants; capture and filter stormwater; expand habitat for birds; and reduce urban heat-island effects. There are two classes of green roofs. "Extensive" green roofs support sedum vegetation and other drought-tolerant plants without irrigation, and are less than 6 inches deep. "Intensive" green roofs can support tall grass and shrubs at 12 inches deep, even crops and orchard trees with a growing medium of several feet.