Start the project by filling out the General Information screens: Project Description, Fuels/Rates, and Weather/Defaults. These screens contain information that is used for all the other sections.

Project Description:

Information entered on the Project Description screen is used only for reports, record keeping and defaults for inputs on other screens. It does not have any effect on calculations. You may skip this screen entirely if report appearance is not important for the project. New/Edit button in the Customerand User areas opens Customer and User libraries respectively. If the customer name and address are the same as the contact person name and the building address, you may use the Same as Contact Person/Building Address button in the Customer area of the screen to copy the information automatically. This situation is very typical for single family houses.


All fuels that are used in the building, or that will be used in the improvements, must be entered on the Fuels/Rates screen. This input is essential for both the Billing Analysis and the Energy Model. You may enter only one rate for each fuel in the project. Enter a usage-weighted fuel cost if you have multiple rates for the same fuel.

  • Fuel: click the leftmost light gray box to open the Fuel Library. Highlight the fuel in the library and click select or double click the fuel to copy it to the input screen.
  • Utility Company and Rate Name are required only if you want to save the fuel rate to the Fuel Rate Library so that you can use it in future.
  • Monthly Flat Fee is the fixed amount that is charged monthly by the utility company in addition to per unit of fuel cost.

Note: that if you have multiple meters for the same fuel you need to enter the total amount for all meters. For example, if there are ten electric meters in an apartment building and each meter has a monthly service charge of $12 you need to enter $120 monthly flat fee. This input is important when model data is compared to billing data.

  • Energy Unit depends on the fuel that you have selected. No custom units are allowed in this field. Btu/Unit is fuel-specific and is used to calculate fuel consumption. TREAT provides a default value and verifies that the input is reasonable for the specified fuel before the data is saved. The user should obtain an accurate value from the fuel vendor.

Energy Units in TREAT:

The Btu content of wood fuel may vary significantly depending on the amount of wood in the cord and the moisture content of the wood. A cord is an approximate unit of measurement representing a pile of logs 4′ × 4′ × 8′, containing air spaces and bark. Rather than being 128 cubic feet of solid wood, a cord may contain as little as 85 cubic feet of wood. The energy content of wood is very dependent on its moisture content. The number in the Fuel Library are for wood with 20% moisture content, a condition achieved by splitting the logs into pieces no more than 8″ wide and allowing the wood to dry with sun exposure and air circulation from the wind for one year. The energy content of wood decreases by one percent for each one percent increase in moisture.

The energy content per Mlbs (1,000 pounds) of steam depends on the pressure of the steam. A utility company may guarantee a system-wide minimum pressure and available pressure may vary at different points in the distribution system. The Btu content of steam generated by a public utility presented in the Fuel Library is for steam at 150 psi gauge pressure, but this assumption must be verified for each specific steam customer.

Energy Cost is the cost of the fuel in dollars per unit of fuel. TREAT only supports one fixed cost per fuel. If the fuel cost depends on total consumption or demand, enter an average value. If utility bills are available, the average cost may be calculated as the ratio of total energy cost (excluding flat monthly fee entered separately) to total energy usage from all available bills. You may further adjust this input after the average cost of fuel is calculated as part of the billing analysis. Energy cost is important because it is used to calculate dollar savings from improvements, as well as improvement SIR, payback and cash flow.

You may enter a fuel by copying it from Rate Library into the current project. Click the View Rate Library button, highlight a rate in the library and click Select to close the rate library and copy the record to the Input Line of the Fuels/Rates screen.


The information on this screen is required for both billing analysis and energy modeling.

Daily Weather Site is used to weather-normalize billing analysis. Select the location closest to your building from the list of sites that you have entered in the Daily Weather Data library.

Importing Daily Weather Data: 

TREAT Provides 2 Options for utilizing the most current daily weather data.

  • TREAT 3.4.6 and above has an updated Daily Weather Spreadsheet tool that allows users to select from over 2000 additional weather sites! It can be accessed by opening the Import wizard on the daily weather tool upload section.
  • TREAT allows users to download the most current daily weather data directly into TREAT. As long as you are connected to the internet simply click Daily Weather Data Library. In the next menu under “locations” select Import.
  • If you wish to download a specific data set or city, you may Import a Daily Weather File using this option and a file saved to your computer.

Long Term Weather Site:

This input is essential for both billing and energy model sections. Select the location closest to your building from the list of sites supported by TREAT. Your selection will direct the program to the appropriate weather file that contains information on typical climatic conditions for every hour of the year. The file is generated based on hourly meteorological data collected for the 30-year period. 12 typical months for each station were chosen from statistics determined by using five elements: global horizontal radiation, direct normal radiation, dry bulb temperature, dew point temperature, and wind speed. TMY3 type weather data is preferred as it provides more sites of more current data. TMY2 sites remain as an option to match older TPGs.

Note:  If you are using TREAT versions after 3.1, but are frequently sharing files with users on earlier versions of TREAT, you will want to select a TMY2 file type.

Heating Season and Cooling Season:

This input determines the months during which heating and cooling systems are available. Heating energy usage during the months that are not part of heating season is equal to zero, even if there is non-zero heating load during these months. TREAT assumes that heating starts on the first day of the heating season start month and ends on the last day of the heating season end month. The same rule applies to cooling.

A PDF containing heating and cooling season months for various locations in the US is available by clicking this link

Heating and Cooling Season:

This input affects both model and billing calculations. Heating and cooling seasons may overlap, for example you may specify heating and cooling season from January to December. Some months may belong to neither heating nor cooling season. Heating season input also affects the way natural ventilation is calculated. See Building Model section Spaces input for more details.

Energy Model Calculation Mode:

This box allows selecting the algorithms used for energy analysis. You may select one of the two available Surface Conductance Algorithms:

  1. R-value +heat capacity for heavy walls algorithm:  this is the optimized version of our previous “layer-by-layer”mode.R-value + heat capacity explained:The algorithm evaluates the material layers in each surface in the project and models each layer either as pure thermal resistance or as thermal mass, depending on layer thickness and material properties. Thermal mass characterizes the ability of material to store significant amounts of thermal energy and delay heat transfer through a building component. This delay leads to several important results, such as lower energy consumption and moving energy demand to off-peak periods. The effect of thermal mass is most noticeable in climates with large daily temperature fluctuations. In heating-dominated climates thermal mass may be used effectively to collect and store solar gains.Note: TREAT Home Energy Rating System Building Energy Simulation Test (HERS BESTEST) testing was performed in this mode. 
  2. Pure Resistances (R-values): this algorithm does not account for the influence of thermal mass.Pure Resistances explainedThis mode was referred to as “Minimize Calculation Time” mode in the versions prior to TREAT 2.5. The mode is retained in order to support projects that were created with the older versions. It is not recommended for new projects since the R-value + heat capacity for heavy walls algorithm provides more accurate results and comparable calculation speed.

Note: R-value + heat capacity for heavy walls mode is the default mode for all projects created in TREAT 2.5 or later. For all projects created in the prior TREAT versions calculation mode is set to pure resistance.

The following Infiltration Algorithms are available:

  1.  Surface Leakage Proportional to Area (Detailed Infiltration) algorithm converts the input entered on Infiltration screen to the total effective air leakage area (ELA).
    1.  ELA is allocated to exterior surfaces entered on Walls/Surfaces screen in proportion with the gross surface area. This algorithm accounts for influence of indoor/outdoor temperature difference, elevation of spaces and surfaces and stack effect. The energy calculations may run slower in this mode. The outputs of the algorithm depend strongly on the shape of the building.


A single story building roof/ceiling may have larger surface area than exterior walls. Because of that, most of the effective air leakage area will be allocated to roof/ceiling, which may result in exaggerated stack effect. Users may adjust the default air leakage assumptions by assigning leakage areas between specific spaces and the outdoors. Fixed Infiltration Rate algorithm assumes that the infiltration rate is unchanged throughout the year and is equal to the value specified on Infiltration screen. The mode increases calculation speed but does not account for indoor/outdoor temperature difference and stack effect. The accuracy of TREAT calculations in this mode was verified by HERS BESTEST.

NoteUse Surface Leakage Proportional to Area algorithm for high-rise building, where the stack effect plays important role. For low-rise buildings, Fixed Infiltration Rate algorithm is recommended.

Default Values:

Selecting from predefined Default Values on the right-hand side of the Weather/Default screen allows the user to speed up the data entry for the energy model. The default value applies only to the components that are created after the default is set. For example, changing the default wall constructions will not affect walls that are already entered in the project, but each new wall created after the default was set would have the new default construction.

  • Default Wall Construction:Wall construction selected on this screen is by default assigned to each new wall that is created on Surfaces/Walls screen. The default value may be edited for each wall on Surfaces/Walls screen.
  • Default Window Frame Type and Glazing Type:Window frame/glazing that you select on this screen will, by default, be assigned to each new window entered on the Windows screen.
  • Default Door Type:The door type that you select on this screen will, by default, be assigned to each new door created on the Doors screen.
  • Default Ceiling Height:The value entered here is used as the default ceiling height of each new space that you create on the Spaces screen.
  • Stories:This input is only used for reports.
  • Number of Dwelling Units:This input is used in domestic hot water demand calculations.
  • Total Number of Occupants:This input is used in domestic hot water demand calculations and for establishing fresh air requirements.
  • Default Building Air Tightness:This input sets the value of Estimated Seasonal Air Changes per Hour in the Heated Area Infiltration section of the Infiltration screen.
  • Use Window Shades in Summer:This checkbox allows the user to specify seasonal window shading. If the box is checked then the shading factor (or SHGC) of all windows in the building are reduced by 20% compared to the value for an un-shaded window entered on Windows screen for all months that are part of cooling season. Using this option reduces building cooling load.
  • Roof Color and Wall Color:These inputs are used to set solar absorptivity of exterior surfaces. The table below shows absorptivity values used in energy calculations depending on the selected surface type and color.
Surface Color Surface Type

Wall Roof
White 0.2 0.2
Light 0.5 0.6
Medium 0.6 0.75
Dark 0.8 0.95


This button allows the user to fine tune the energy model inputs:

  • Shielding Class:This strongly affects infiltration calculations if Detailed Infiltration algorithm is used.
  • Common Wall Area:This input is used in calculation of HERS rating of attached homes.
  • Entering Cold Water Temperature:This input is used in domestic hot water calculations for the model. A PDF with various entering cold water temperatures around the US is available here
  • Average Lighting Load:In units of Wh/SqFt-Day this input is used in Model Inspector to verify accuracy of lighting inputs.
  • Cooling Latent Load:This input is used for the load sizing and cooling energy calculations
  • Account for climate impact on HSPF and SEER:This checkbox adjusts the manufacturer-specified HSPF and SEER to account for site climate. The nameplate HSPF for a heat pump is based on the temperature in Climate Region IV (Pittsburgh, PA) and the minimum Design Heating Requirement (DHR) that is a function of machine heating capacity. This selection limits the contribution of resistance heating because it typically results in relatively high seasonal heating temperature. Site specific HSPF varies significantly with climate. All unitary air conditioners are rated using EER, a rating standardized by ARI, which reports steady-state efficiency at 95oF outdoor and 80oF indoor temperature. Smaller air conditioners (i.e., < 65,000 Btu/h) are also rated using SEER, intended to better indicate average seasonal performance. However, for single-speed equipment, SEER is simply estimated as the EER at 82°F outdoor and 80°F indoor temperature condition. SEER rating de-emphasizes high temperature performance. The TREAT climate efficiency degradation algorithm accounts for variations of actual equipment efficiency based on its rated efficiency and the climate at the building site. We recommend that this adjustment is used for all TREAT projects.
  • Account for Part Load System Efficiency:This checkbox adjusts model heating and cooling energy consumption to account for reduced efficiency during part load operation. The algorithm was developed based on information presented in the article “Residential Equipment Part Load Curves for Use in DOE-2” by Henderson, Huang and Parker. Part load ratio for each month was calculated by dividing monthly heating (cooling) load by the energy that the heating (cooling) system could generate at full load conditions during the same time interval. The part load adjustment is calculated for each month depending on equipment type and part load ratio during the month and varies between 0.75 and 1. If part load ratio for boilers is less than 0.1 then monthly usage is adjusted by 0.75 + 2.5 × PartLoadRatio. For forced air heating and cooling systems the monthly usage is adjusted by 0.75+0.25 × PartLoadRatio.