In the fall of 2008, Michaels Energy moved into the second floor of the 100 year old, former downtown department store, Doerflinger’s.  The space was completely renovated including refurbishing the original maple floor, repairing plaster, replacing glazing in the original windows, and installing an efficient heating and cooling system with condensing boilers, water-cooled chiller and variable frequency drives on nearly all pumps and fans.  By mid-winter, Michaels’ gas bills showed literally about one quarter of the gas consumption that the third floor was experiencing – 299 ccf versus 1,228 ccf.  The third floor has nearly identical floor space (14,000 square feet), glazing, and exterior exposure and a similar variable air volume (VAV) heating and cooling system.  The building owner asked Michaels to investigate the cause of this apparent wasted energy.  Knowing the system type, the target before investigating was excessive VAV box reheat.


The third floor included a substantial data center with waste heat available for free heating of the third floor.

Within minutes, Michaels had determined that the distribution system for that heat recovery system was causing the adjacent space to “over heat”.  This was driving the entire central system for the floor into cooling to cool that space.  Not only was this resulting in excessive zone reheat for all the other zones, it was canceling the heat recovered from the data center.

The solution: take the temperature sensor serving the adjacent space off the system.  Disable it.


Gas consumption immediately plunged.  Savings are approximately 50%.  Payback period: instantaneous.  This prompted the tenant of the floor to replace their control system to provide functionality that is more similar to the Michaels’ system.  This generates even greater savings[1].

[1] Michaels and the third floor share chilled water, which is not sub-metered.  Therefore, electric savings are much less discernable.