MEP Engineering · Engineering Glossary
An HVAC load calculation determines the amount of heating and cooling energy required to maintain a building's interior at design temperatures under peak weather conditions. Load calculations are the fundamental basis for HVAC system sizing and must be performed by a mechanical engineer before equipment can be selected.
The cooling load calculation accounts for heat gain through the building envelope (walls, roof, glass), solar gain through windows, internal heat gains from occupants, lighting, and equipment, and outdoor air ventilation loads. The heating load calculation accounts for heat loss through the building envelope and the energy required to heat outdoor ventilation air. ASHRAE methods (CLTD, RTS, or HB) are used for commercial buildings; the Manual J procedure is used for residential. Undersized equipment leads to uncomfortable spaces; oversized equipment short-cycles, reducing efficiency and humidity control. Building permit submittals for HVAC often require a load calculation report. Apex Grid performs load calculations as the foundation of all mechanical engineering work.
Apex Grid Engineering maintains this glossary as a resource for architects, contractors, developers, and property owners who encounter unfamiliar engineering terminology on their projects.
View All Engineering TermsApex Grid's licensed PEs provide mep engineering services across multiple jurisdictions — with fast quote turnaround and permit-ready documents.
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