Sustainable Building Technical Manual - Etn-presco.net

Plumbing Systems★ S I G N I F I CA N C E .Water use in buildings has two environmental impacts: (1) the direct use of water, a limitedresource; and (2) the expenditure of energy used in water pumping, purification, treatment,and heating. This section considers the energy-use aspects associated with waterusage within a building, including pumping and hot-water heating (see also Chapter 11,“Renewable Energy”). Other chapters discuss additional water-use strategies, such as graywatersystems and landscape irrigation (for example, see Chapter 6, “Water Issues”).The overall amount of energy used to pump, treat, and heat water can approach 10 percentof a utility company’s output. The primary areas where improvement is possible are:(1) more efficient water generation and end-use devices, (2) reduced storage losses in hotwaterequipment, (3) reduced piping and pumping losses, and (4) reduction in hot-watertemperatures to provide the minimum acceptable temperature for intended use.. ☛ SUGGESTED PRACTICES AND CHECKLISTIHot-Water Heating❑ Consider hot-water heating options.Analyze and specify efficient equipment options. Heat pumps, heat recovery processes,tankless water heaters, and combination space heating-water heating systems areoptions that can improve efficiency significantly.❑ Reduce hot-water system standby losses.Losses from distribution piping and hot-water storage tanks can be more than 30 percentof heating energy input. Tank insulation, anti-convection valves and heat traps, aswell as smaller heaters with high recovery rates, can reduce these loss factors.❑ Evaluate system configuration.Consider the benefits of localized hot-water equipment versus centralized equipmentby evaluating the types of loads served. Localized heating equipment options for smallisolated loads may include electric heat-tracing devices which use a linear-resistanceheating element wrapped around the piping.❑ Reduce hot-water service temperatures.Confirm the lowest hot-water temperature needed for the usage or equipment.Lowering the hot-water supply temperature reduces initial heating-energy and systemlosses. This approach should be limited to a minimum water temperature so as not toallow growth of harmful bacteria in piping.❑ Install hot-water system controls.Appropriate controls optimize energy use. Time-of-day equipment scheduling is a basicfunction; the use of certain applications may benefit from temperature optimizationfeatures.❑ Consider solar hot-water heatingConsider solar systems based on building type, hot-water needs, and solar conditions atproject site (see Chapter 11, “Renewable Energy”).Water-Pumping Systems❑ Use low-flow plumbing fixtures.Low-flow fixtures may seem to be a water conservation method, but they also saveenergy because they reduce pumping energy and water heating. Products are availablefor a wide range of applications and have become standard in many areas.