The simplest method to study the performance of a building without modeling a full HVAC system is by utilizing the Ideal Air Loads HVAC system. This piece of zone equipment is not connected to a central air system (no need to specify air loops, water loops, etc.) and instead supplies sufficient cooling or heating air to a zone to meet its load or up to its specified limits. The system has options for humidity control, outdoor air, economizer, demand-controlled ventilation, and heat recovery. It is 100% efficient, always available, and has infinite capacity. By default all new Zones will be assigned to Ideal Air Loads. Zones can be manually assigned to Ideal Air Loads during the modeling process in the Project Data Editor.
Within loadmodeling.tool, the ideal air loads system is modeled as an ideal VAV terminal unit with variable supply temperature and humidity; the supply airflow ventilation rate is varied between zero and the maximum in order to satisfy the heating or cooling load, humidity controls, outdoor air requirements, and other specified constraints. This system acts as the default system for the building if no Zones or Air Systems are specified. If running the model without considering Zones, the Project Data Editor and Air System page should be skipped, and the model will run using the Ideal Air Load system assigned to every room of the model.
When running an ideal air loads system, the ventilation load is reported in the Peak Load Breakdown within the Detailed Cooling/Heating Load Results tab on the Results page, which is not the case for projects with zones supplied by non-ideal air systems.