Identify fume hoods with the biggest savings potential. Not all fume hoods are equal!

 I quickly found out the level of complexity in calculating fume hood operational cost.  Are they CAV or VAV?  Do they drive lab exhaust, or can the HVAC system work with the hoods to balance the air change rates effectively?  There are a number of variables that determine fume hood operational cost, but for the most part shutting the sash on a VAV fume hood will more often than not yield savings.  Some departments also have automatic sash closers on their fume hoods, so I wanted to discover if these closers are more efficient than the competition in yielding savings.  It was found that labs with the automatic sash closers tend to dislike them, saying that they are annoying and they "beep a lot.”  "Some of the scientists actually disable the automatic closing mechanism" according to former lab building manager Paul Tighe. I decided to conduct a comparison between fume hoods in the competition, those with automatic closers, and those with neither to see which faired best at saving energy.

We also had to do a comparison between normal lab activity, and poor sash management.  We determined that any sash opening that was five hours or less would be treated as "normal operation." Excessive sash openings of five plus hours were considered “poor behavior,” and the costs were calculated.  It is important to note that Shut the Sash started in the Department of Chemistry & Chemical Biology, and those labs typically have many more fume hoods, and are accessed more frequently on a daily basis for research.  The results of the three month study concluded that the average operational cost of a fume hood participating in the Shut the Sash competition was $1,858 per year, while the fume hoods outside of the competition cost approximately $3,039 to operate per year.  The fume hoods with automatic sash closers cost an average of $1,716 per year to operate, however, those fume hoods were not accessed as often as those in Shut the Sash.  This indicated to us that Shut the Sash outperforms automation as an energy savings approach, and that expansion of the competition was the optimal energy saving strategy.  It also validated the cost and energy savings of the original Shut the Sash competition, which continues to save over $200,000 per year.