A Critical Look at Cold Supply Air Systems

Stephen W. Duda, PE, LEED AP BD+C, BEAP, HFDP, HBDP, ASHRAE Fellow
Project Manager/Senior Mechanical Engineer

In the course of a 30-year career, this consulting engineer has been asked to retrofit, remodel, modify, or study the HVAC systems of many existing buildings designed by other engineers. Occasionally, that existing HVAC system has been a colder-air variable air volume (VAV) system, sometimes using a supply air temperature (SAT) as cold as 44°F (6.7°C). While realizing almost any common HVAC choice has pros and cons, I have on those occasions pondered why the original engineer would have selected such a cold SAT. Additionally, from time to time, I see magazine articles or vendor presentations promoting colder SAT, which is usually contrasted with conventional air at or about 55°F (13°C). With recent advances in high-performance VAV systems and dual-maximum VAV damper controls, it is time to revisit that concept.

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This article was published in ASHRAE Journal, December 2016. Copyright 2016 ASHRAE. Posted at www.ashrae.org.