Service Hot Water (SHW)

Full loadmodeling.tool workflow rundown for modeling SHW

Akshay Padwal avatar
Written by Akshay Padwal
Updated over a week ago

Service Hot Water (SHW) systems, often overlooked in the larger energy efficiency conversation, play a pivotal role in ensuring occupant comfort, hygiene, and health. They are responsible for providing hot water for everyday activities - whether it's a morning shower, washing your hands, or running a dishwasher. With their integral role in energy use, these systems' efficiency can have a significant impact on a building's total energy demand. Hence, a comprehensive building energy model needs to carefully consider the SHW systems' characteristics, their usage patterns, and the efficiency of the associated heating and distribution equipment.

Within the platform, there are couple of ways to model Service Hot Water for the project building:

Per Room SHW Modeling Method

  • Based on the room templates assignment, the SHW inputs will be loaded by default to the project

  • From Auxiliary Inputs page, select a template for Service Hot Water plant.

  • Under Service Hot Water Parameters section, make sure that the Calculation Type is set to Per Room.

  • Customize any plant inputs as needed

  • Multiple plants can be created and then assigned to specific zones from the Project Data Editor page

Per Plant SHW Modeling Method

This method is a high-level approach for modeling Service Hot Water. This method is ideal when a total plant-level information is available for the project.

Important Note: Choosing this option will override any zone specific assignment for the Service Hot Water if switched from 'per room' default

  • When a plant is added on the Auxiliary Inputs page, switch the Calculation Type of Service Hot Water Parameters to Per Plant

  • Selecting Per Plant option will reveal Plant Peak Service Hot Water gpm and Project SHW Schedule inputs

  • Edit these inputs based on the plant-specific information. Plant Peak Service Hot Water value can be edited in directly.

  • A default schedule will be loaded for Project SHW Schedule input. If one needs to be created from scratch, add it within Schedules page with an Equipment type and then assign it from Project SHW Schedule input.

Accessing the Results

Plant Sizing Results

Mechanical Plants results tab will display the sizing results for Water Heater and pumps.

Default Flow Rates

Service Hot Water use in a building can be difficult to estimate. One method is to consider the flow per person in each zone and then associated the usage with an occupancy style schedule. On our platform there five default flow rates that are assigned at the Room Template and used if the system is following the Per Room method. These values come from ASHRAE Handbook Applications - Chapter 51, Table 6 and are converted into flow per person as show here.

SHW Category

Flow Rate



0.0066667 gpm/person

0.0004206 l/s/person

Table 6 - Office Buildings


0.0066667 gpm/person

0.0004206 l/s/person

Table 6 - Office Buildings


0.016667 gpm/person

0.001051 l/s/person

Table 6 - Junior and Senior High Schools


0.07500 gpm/person

0.00474 l/s/person

Table 6 - Apartments Houses 50. 2 people per Apt


0.08333 gpm/person

0.00525 l/s/person

Table 6 - Nursing Home

Note that in some cases these values may be higher than expected for a given project and the SHW energy use will appear too high. If this occurs on your project we recommend modifying the default values based on project information, or utilizing the Per Plant method if the expected flow for the project is already known.

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