Models

Here is a list of models used in the Scoring Tool.

Heating and Cooling

EnergyPlus™ is a is free, open-source, cross-platform, whole building energy simulation program that engineers, architects, and researchers use to model energy consumption for heating, cooling, ventilation, lighting and plug and process loads, and water use in buildings. EnergyPlus™ uses a description of the building layout, constructions, operating schedules, conditioning systems (lighting, HVAC, etc.) with weather data, to perform an hourly simulation of the building and to estimate utility use. See the EnergyPlus™ documentation.

Water Heater Model

Total hot water used is the sum of clothes washer, dishwasher and fixture related usage. These are determined based on the estimated number or occupants in the house. EnergyPlus™ calculates the domestic hot water use using the ANSI/RESNET/ICC 301-2019 standard.

Infiltration Model

EnergyPlus™ uses the AIM-2 “ASHRAE Enhanced” model to calculate the effects of infiltration on energy use.

Weather

Home Energy Score uses TMY3 data to account for the local weather. The house zip code is mapped to the closest TMY3 weather station to calculate energy use.

Model Defaults

Home Energy Score is an asset rating; therefore, the influence of the occupants must be standardized so houses can be compared on an apples-to-apples basis. To do this, Home Energy Score assumes the following default characteristics for each house.

  • Occupancy is determined based on the number of bedrooms using this equation (#bedrooms + 1, from the ANSI/RESNET/ICC 301-2019 standard). Using this method, the number of bedrooms directly affects the household’s amount of estimated domestic hot water consumption. Further, occupancy is used to determine miscellaneous electric loads such as television.

  • Stove, oven and clothes dryer are assumed to be electric.

  • Appliance, lighting and miscellaneous plug loads are calculated in EnergyPlus™ using the ANSI/RESNET/ICC 301-2019 standard.

  • The building length and width are fixed to a 5:3 aspect ratio.

  • The thermostat schedule is defined based on the ANSI/RESNET/ICC 301-2019 standard where heating is 68F and cooling is 78F.

  • To calculate estimated energy savings in dollars, the Tool uses state average utility rates as provided by DOE’s Energy Information Administration.