Similar to space heating, water is heated in the building for various uses including cooking, cleaning and bathing. A water heater is an appliance that typically uses either a gas burner or an electric heating element to heat water.
According to U.S. Department of Energy (DOE) and various surveys like Residential Energy Conservation Survey, water heating solely uses more than 20% of a home's energy use. For a K-12 school, as per the Advanced Energy Retrofit Guide, while the percentage might be lower as compared to homes, water heating along with some other plug loads can account for up to 15% of the building energy use. Additionally, the second largest end use of natural gas in various buildings is water heating.
There are three major ways of reducing water heating energy consumption:
- Selecting the appropriate fuel and water heater type,
- Using an efficient system design, and
- Reducing hot water consumption.
Opting for a higher efficiency water heating system (for example, ENERGY STAR certified), improving the efficiency by insulating the existing storage tank (for example, adding an insulation blanket) and pipes (for example, insulating by 1inch for pipes less than 1.5inches, otherwise by 1.5inches) and decreasing service hot water temperature or even installing automatic temperature controls wherever viable are various ways of minimizing the utility bills. One of the recommendations implemented in Asset Score/QBAT is as follows:
Asset Score Report Recommendation: Install low flow water fixtures
A low-flow fixture is a water-saving plumbing device that uses less water or a smaller amount per flush. Examples include showerheads, urinals, toilets and aerated faucets.
Before 1980, toilets used either 7 gallons per flush (gpf) or 5gpf. The standard changed to 3.5gpf after 1980, and in 2002, the federal standard for new construction became 1.6gpf toilets, designed to increase flush velocity using gravity or pressurized flush water. DOE adopted a 2.2gpm (gallons per minute) for private-use lavatory faucets and kitchen faucets in 1998. Various aerators for faucets including a standard, spray, rain spray and laminar flow are available in the market with varying flow rates.
Upgrading older fixtures to meet this standard can lighten the utility load and lower facility costs. Various national level as well as U.S. Environmental Protection Agency's (EPA's) flow rates and specifications for faucets, showerheads and other fixtures can be found on the EPA website - https://www.epa.gov/system/files/documents/2023-06/ws-commercial-watersense-at-work_Section_3.3_Faucets.pdf.
Water-saving fixtures not only decrease water usage but also reduce the energy required to heat the water.