MEP Engineering · Engineering Glossary
A Rooftop Unit (RTU) is a packaged HVAC system mounted on a building's roof that contains all heating, cooling, and ventilation components in a single enclosure. RTUs are the most common HVAC system type for low-rise commercial buildings such as retail, office, and light industrial.
RTUs connect to the building's duct system through a roof curb opening, supplying conditioned air and returning room air for reconditioning. From a structural perspective, an RTU replacement or new installation requires an engineer to verify that the roof structure can support the equipment weight (often 500–2,000+ lbs), design the structural curb or dunnage, and confirm that the roof deck or framing is adequate. From an MEP perspective, the engineer sizes the RTU for the cooling and heating loads, selects the appropriate efficiency, and designs the duct connections. Apex Grid provides both the structural and mechanical engineering required for RTU projects.
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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