Overview

In this step, you will define internal loads for the zones that were defined previously in the zoning map. There are three types of internal loads: lighting, electric equipment, and people. Lighting and electric equipment consume electricity and add heat to the zones. People add heat but are not direct consumers of electricity. Two parameters are required to define each type of internal load for each zone: a density (or peak loading) and a schedule, which modifies the peak load on a repeatable weekly pattern. Densities and schedules for each zone come pre-populated with defaults according to the zone type chosen previously.

In most cases, a modeler may not have specific knowledge of the zone loading patterns required to set accurate densities and schedules. In these cases, sticking with the pre-populated defaults may be a good strategy. Densities and schedules may be re-evaluated later in the process of calibrating your baseline model, if possible. In the meantime, an appropriate step for modifying the default schedules is to validate that the schedules roughly align with known occupancy patterns in the building.

In-Depth

For each zone with exterior walls (or for the building as a whole), enter the window-wall ratio (100% for full glass, 0% for no windows). This can be determined accurately through an analysis of architectural elevation drawings but, for the purposes of this tool, can be simply estimated visually using pictures of the building exterior.

Review the default schedules that are pre-populated for each zone based on the zone type that was chosen. Compare the ramp-up and ramp-down times in the schedules to known patterns of building (or zone) occupancy. Modify the schedules to reflect these patterns. The default schedules may have assumptions about weekend patterns that do not match the actual building. Make sure that weekend patterns look reasonable, or re-adjust as necessary.

Note that buildings that are occupied 24/7 often have lights on continuously (unless there are occupancy sensors). However, occupant densities in commercial buildings are still likely to be significantly higher during the daytime. Therefore, even in 24/7 occupied buildings, people and electric equipment densities should follow a base-to-peak loading schedule that correlates with likely periods of high and low occupancy.

For residential buildings, the peak loading of people is likely to be at night, with peak lighting and equipment loads during the mornings and evenings.