Designing Quiet HVAC Systems   Standards have been developed by ASHRAE (American Society of Heating, Refrigeration and Air-conditioning Engineers) which provide acceptable noise levels as Noise Criterion (NC) and Room Criterion (RC) curves. These have been used as industry standards for addressing noise within every environment.

We provide recommendations to project architects and mechanical engineers in regards to supply/return mechanical equipment noise, radiated noise, vibration isolation, ducted break-out noise, and mechanical room noise and vibration. Typical Evaluation Supply, intake and radiated noise of air-handling units are evaluated from the location of the equipment. Accurate predictions are made based on ducting and air distribution elements. These provide a starting point for recommendations to achieve the Noise Criteria. We provide detailed recommendations supported by CAD details, specifications, and field evaluations during construction. Recommendations typically include duct liner, silencers, plenums, equipment location, and ducting layout. Application The evaluation of noise from these systems is applicable to most occupied buildings. Spaces such as theaters, schools, courthouses, hospitals, churches, and residences are sensitive environments for control of HVAC noise.

Common issues we find are radiated noise from rooftop mechanical equipment located over classrooms or office spaces, and supply and return ducting generating unacceptable noise levels within sensitive spaces. The use of VAV boxes and terminal units above office spaces and meeting rooms necessitate mitigation measures to achieve acceptable noise levels. When completed in design, these changes normally have minimal impact on the system cost.