Overview

In this step, you will identify high-level details of the building, its location, the type of heating and cooling plant, and its envelope. Many of these details are very difficult to quantify, and wherever possible, defaults and qualitative designations that pertain to quantitative estimates are available.

In-Depth

Guidance for the following building-level details is as follows:

• Primary Cooling Type: This is the ultimate source of cooling for the air handler (and zone-level cooling if applicable). Choices are: chillers, DX coils, and heat pumps. A DX unit uses refrigerant-based cooling and cools indoor air using a condensed refrigerant liquid. Direct expansion means that the refrigerant expands to produce the cooling effect in a coil that is in direct contact with the conditioned air that will be delivered to the space. This includes systems such as packaged rooftop units and variable refrigerant flow systems. A fourth option for this input is “Free (Accounted for Elsewhere).” This is an option that is intended to account for buildings where the chilled water plant is located in an adjacent building or somewhere else on campus, and the modeled building is not metered for the use of its cooling.
• AHU Heating Type: This is the ultimate source of heating for the air-handler heating coils. Choices are: Boilers, district heating (steam), heat pumps, and electric resistance.
• Zone Heating Type: This is the ultimate source of heating for zone-level heating coils. Choices are: Boilers, district heating (steam), heat pumps, and electric resistance.
• Vintage: The year the building was constructed. Used to select an appropriate energy code for envelope characteristics.
• Climate Zone: The DOE Climate zone location of the building. A map is provided to help with this selection. Used to identify appropriate energy code defaults for window and wall characteristics.
• Framing: Are metal or non-metal structural components used for load-bearing purposes and wall studs? Used to identify appropriate energy code defaults for window and wall characteristics.
• Building Construction Type: What is the nature of exterior walls. Mass walls are generally concrete or heavy brick, Steel framed versus wood framed reflects the previous question about framing. Used to identify appropriate energy code defaults for window and wall characteristics.
• Wall U-factor: This can be specified if known. Otherwise, an appropriate value will be selected from ASHRAE 90.1 tables.
• Window U-factor: This can be specified if known. Otherwise, an appropriate value will be selected from ASHRAE 90.1 tables.
• Window SHGC: This can be specified if known. Otherwise, an appropriate value will be selected from ASHRAE 90.1 tables.
• Construction Thermal Mass: This variable affects the thermal inertia of the zones in the simulation. When defining the baseline building, this parameter can be specified as a qualitative designation (light, medium, or heavy). This will lead the model to select a corresponding quantitative value for thermal mass. If unknown, medium is a good choice. Otherwise, the following rough qualitative descriptions describe various levels of thermal mass:
  • Light: Steel frame and glass construction, spacious, open office
  • Medium: lightweight concrete construction, typical interior furnishings
  • Heavy: heavy concrete construction, dense interior furnishings (wood, laboratory/hospital equipment, narrow corridors, small open spaces)
  This value can later be modified in the calibration process.
• Envelope Tightness: This qualitative field is used to select an appropriate quantitative value for the rate of outdoor air infiltration through the envelope. “Tight” corresponds to 0.2 cfm/sf, “Average” corresponds to 0.4 cfm/sf, and “Leaky” corresponds to 0.6 cfm/sf.
• Building Pressurization Fans Present: Some buildings have dedicated exhaust fans that are used to maintain desired building static pressure. These fans are typically variable speed and respond to a building static pressure setpoint by increasing or decreasing their speed.
• Miscellaneous Building Exhaust Fans Present: Most buildings have miscellaneous building exhaust fans, especially for restrooms, but often serving other niche spaces.