Ask the Energy Experts: Reduce energy use in commercial bathrooms

Can you recommend ways to save energy in commercial bathrooms?

Commercial bathrooms offer many opportunities for energy savings. Bathroom efficiency measures can have a positive effect on any business, but hotels, schools, recreation centers and other facilities with large multiple bathrooms can really benefit from the following measures.

Insulate piping
Most codes require insulation for hot-water piping, but insulation may have been damaged or removed during maintenance operations. Replace it with the minimum insulation required by your jurisdiction’s most recent energy code, or better. For example, the Washington State Energy Code requires a minimum of half an inch of insulation, with a conductivity between 0.24 and 0.28 (roughly R-4 per inch) for supply lines up to 2 inches in diameter, and 1-inch insulation for piping up to 4 inches in diameter.

Reduce flow
Reduction of domestic hot water (DHW) consumption can be accomplished by limiting the flow rate from fixtures, automatically shutting off the hot (and cold) water after a measured time interval and reducing supply temperatures. The first two measures are required by most plumbing codes for facilities open to the general public. Flow rates are usually limited to 2 gallons per minute (gpm) with the requirement that the valve self–close within 30 seconds. Self-closing faucets can save money and energy – and prevent vandalism. Also, the Building Energy Software Tools Directory, by the Department of Energy, provides links to several useful general water conservation software tools.

Reduce temperature
Many codes and statutes also limit the maximum temperature at lavatories in commercial buildings to 120 degrees. Resetting the water heater thermostat to deliver 120-degree water is usually a simple and cost-effective way to save energy in bathrooms. For water heaters serving additional, higher temperature hot water loads (dishwashers, etc.), equip the fixture with a thermostatic mixing valve or a booster heater for the higher temperature loads.

Control recirculation
Larger commercial buildings usually have systems to recirculate hot water from the most remote hot water fixture back to the water heater. The idea is to keep the water in the distribution piping hot at all times and reduce the time a user must wait for hot water. Many state and federal energy codes now require a time clock or other automated means to shut down the hot water recirculation pump during unoccupied hours. These controls save energy by eliminating heat loss from the recirculation piping when the building is unoccupied. They also cut the run time and electrical consumption of the recirculation pump by almost half.

Upgrade lighting
Bathrooms are occupied only intermittently, usually less than 20 percent of the time. That makes bathroom lighting in a commercial establishment the perfect application for occupancy sensors that turn off the lights when the bathroom is not in use.

Recover heat
Exhaust systems are another energy-user in bathrooms. In larger commercial buildings, a single fan often serves several bathrooms and it runs during the occupied hours. In small commercial buildings, the exhaust fan is often wired to the light switch and only runs when the lights are on. This can lead to under-ventilation of the bathrooms and indoor air quality (IAQ) problems. Modifying light switch-operated fans to run during the occupied hours will increase building energy use slightly, but will improve IAQ.

You can make up that loss by using the moist exhaust air leaving the building to preheat (or cool) outside air. Learn more about heat recovery ventilatorsRedirecting to a non-government site, from the Energy Efficiency Emerging Technologies Database. This collection of practical, commercially available, but not yet widely used energy efficiency technologies is regularly reviewed and evaluated by energy experts and engineers.

Upgrade heating system
Bathrooms are usually located in the core of larger buildings with no outside walls. However, some smaller buildings have bathrooms on outside walls that need to be heated in winter. The heat source for outside wall bathrooms is often an electric resistance heater that runs constantly. Consider installing a programmable thermostat (line voltage or 24v. as appropriate) or a connection to the building energy management and control system to limit operating hours and save energy.