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:

• Building Floor Area: Enter floor area for the entire building, excluding any spaces that are not part of the official floor area of the building. Used for calculation of energy use intensity (for example, parking garage area).
• Location (Latitude): This input can be left blank, and if so, the latitude will be imported from the weather file. This variable is used to estimate solar loading on each of the building’s exterior walls.
• AHU Total Design Airflow: This is an optional input because the total design airflow for all airside systems is not always known. This value should reflect the sum of the design sizing for all air handlers and/or primary air-delivery systems for heating/cooling and/or ventilation in the building or modeled section of the building. If left blank, the model will size the system based on peak zone loads, the square footage specified, and a specified fraction of the total floor area that is being modeled.
• 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.
• 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.
• 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.
• Infiltration: Infiltration is outdoor air that is exchanged directly with the interior building zones. This can be specified qualitatively. “Low” corresponds to 0.01 cfm/sf.