One of the best pieces of advice I was given 17 years ago starting out as a young building engineer was that buildings act much like living breathing things. My mentor instructed, "You need to watch how they respond when you make changes." In this tutoring session, he was talking about adjustments to the building automation system or turning on/off equipment - monitoring the building differential pressure, water temperature flows, etc. Another part of understanding how the building responds is not so instantaneous but rather an effect on equipment operation over time.
By performing preventive or predictive maintenance, you are having a check up performed: test the vitals, check the blood, and assess overall heath and condition. In our buildings, monitoring operating conditions can help understand what may be going on with our equipment. Sometimes failure occurs and it's clear a new system is needed. In other cases, the equipment continues to operate, drain the budget, and limp along. Is the air temperature that was once able to stay comfortable now always fluctuating? Do you continue to have problems with the same cooling systems?
Matt Napolitan and Brent Weigel of Cx Associates http://www.cx-associates.com/ developed a helpful checklist of scenarios where you can benefit from an engineered retrofit. An engineered retrofit is a replacement or upgrade of equipment or systems right-sized alternative tailored to today's end use requirements. These are 8 examples of when to consider engineered retrofits: