The U.S. Green Building Council’s Leadership in Energy and Environmental Design Rating System (LEED™) is a certification and standard-setting program which requires energy benchmarking and disclosure, and the potential energy savings of a building to be quantified.
In addition to assessing lighting and power reductions, energy efficient motors, reducing domestic water requirements, one small segment of the overall energy modeling requires you to calculate the hot water consumption for your building. The calculations for the LEED energy efficiency incentive program should compare the baseline mandated amount of hot water (which is determined by code requirements for energy efficiency) versus the reduction achieved when using reduced flow faucets. While it might seem like an easy number to calculate, a bit of thought and research might be needed to arrive at this value.
Domestic Hot water Consumption First of all: in addition to data for sinks, toilets and showers that are required to obtain LEED Water Efficiency credits, all other other hot water usage fixtures – such as mop receptors, clothes washers, dishwashers, commercial kitchen sinks and dishwashers – must also be included for the overall determination of domestic hot water usage.
In order to set the baseline numbers, use of an acknowledged standard is required. One option is to use the ASHRAE Handbook – Service Water Heating chapter. This chapter gives you the baseline information required to set up a LEED calculation based on the type of building and the hot water usage of each type of fixture for that building type.
The project-specific information shall come from various fixture selections. The plumbing fixture schedule should give you this information as part of the supplied information, or you might need to consult the manufacturer’s website to find out the catalog information based on the model number.
Baseline vs. Installed Hot Water Heating Systems Another item that needs to be determined for the LEED Energy Analysis involves the establishment of a baseline and installed hot water heating system. Again, the baseline hot water heating system can be calculated using information found in the ASHRAE Handbook. Specifically, the energy professional should look for the baseline fixture information to arrive at a calculated baseline storage volume. The storage volume for the installed hot water heating system can be found in the plumbing equipment schedule for the project.
Determining Reduced Usage Some mathematics is also required to determine the reduced usage needs. Excel is an excellent tool to use that will allow you to adjust information quickly and easily should the need arise. To give you an idea, here’s an example of a domestic hot water calculation our LEED-certified energy professionals recently performed:
Adding an assessment of domestic hot water consumption to your overall LEED Energy Analysis calculations will not only allow you to fully understand your building’s energy usage, but will also help you to identify areas and measures to improve energy efficiency, reduce costs and help you to qualify for a LEED certification!