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Do the math: Multi-parameter DCV Systems Usually Worth the Cost

Oct. 10, 2017
High first costs can sometimes seem to be a deal-breaking hurdle for customers seeking the proper ventilation system for their business, but one lab's recent experience further confirms why the author is still sold on Mp DCV systems.

In the August 24, 2017 posting to this blog, I prefaced my comments about demand-controlled kitchen ventilation by mentioning my long-time professional interest in demand-controlled ventilation (DCV) in general. It is a topic about which I have frequently written and lectured, beginning with an article in HPAC Engineering in August 2009, in which I described the concept of multi-parameter DCV (Mp DCV). Much of that article was based on technology originally developed by Gordon Sharp, a 25-year veteran of airflow controls innovation with dozens of US patents, that led to his formation of Aircuity ( in early 2000.

At the time, I was working for one of Florida’s largest HVAC contractors, and our fledgling energy solutions group was actively promoting Aircuity’s Mp DCV system, known then as OptiNet. Although the simple payback periods for the right applications (particularly laboratories) were very compelling, there nevertheless was a lot of sales resistance, even from knowledgeable prospects. Much of that resistance was due to the relatively high first cost, compared to conventional DCV that used only CO2 sensors. However, some of the push-back apparently was also due to the recurring annual system maintenance commitment that the manufacturer recommended.

Aircuity recently reported an experience that clearly demonstrates the concerns that prospects and customers may still have about long-term system maintenance commitments. Their Mp DCV system had been operating in a large laboratory for more than seven years and the laboratory, according to the customer’s own calculations, had avoided nearly $1 million in the energy costs associated with its previously high ventilation rates. The lab had been running 12 air changes per hour (ACH), but with the installation of Mp DCV, had been able to reduce the normal ventilation rate to 4 ACH, with the ventilation rate ramping up to 12 ACH when an out-of-limits air quality event was detected. The customer was now, however, considering manual operation of the lab ventilation at a constant 6 ACH, thus (in their thinking) eliminating the need for Mp DCV. They were of the opinion that the avoided energy cost saved by Mp DCV was approximately the same as the cost of the maintenance agreement, and that 6 ACH was a reasonable compromise.

After a detailed analysis of operations, it was found that the lab was experiencing well over a thousand air quality events – either high volatile organic compounds (VOC) or high particle counts – every month, and that operating at a constant ACH equal to only 50 percent of the ventilation system’s maximum capacity would not clear the pollutants from the affected spaces as quickly, or as safely, as would the Mp DCV system. It was also discovered that many of the lab areas could be operated at only 2 ACH during unoccupied periods, providing additional savings to offset the cost of the service agreement. 

Not surprisingly, after reviewing the data, the customer decided to retain (and upgrade) the Mp DCV system in place. One can only speculate as to whether it was safety concerns or the financial considerations, or both, that drove their decision. Of course, those of us in the HVAC industry – and this is particularly true for service contractors – know that maintenance agreement sales can be challenging.

However, if the business case clearly supports the purchase, as in the instant example, it should be a no-brainer.

About the Author

Larry Clark

A member of HPAC Engineering’s Editorial Advisory Board, Lawrence (Larry) Clark, QCxP, GGP, LEED AP+, is principal of Sustainable Performance Solutions LLC, a South Florida-based engineering firm focused on energy and sustainability consulting. He has more than two dozen published articles on HVAC- and energy-related topics to his credit and frequently lectures on green-building best practices, central-energy-plant optimization, and demand-controlled ventilation.