Executive Summary

The iCAP recommends establishing a program to educate users of variable air volume chemical fume hoods (VAV CFH) to encourage lowering the sash when not in use.  Theoretically, this collective action by users should reduce building air flow and its associated energy costs and carbon emissions.  Preliminary studies done at U of I, however, have not been able to demonstrate reduced energy consumption when CFH sashes are lowered.  Some ventilation control systems are not properly designed to maximize efficiency.  Further, not enough is known about overall building energy consumption and the interrelationships between various contributing factors to develop metrics for measuring success in reducing energy costs.  It is recommended that before any action is taken to educate users, background studies should be done to allow more effective control of CFH systems and to more accurately measure the effectiveness of interventions.

Introduction

In May 2010, the University of Illinois (U of I) published iCAP, Climate Action Plan for the University of Illinois at Urbana-Champaign in an effort to fulfill its obligation to the 2008 American College & University President’s Climate Commitment.  The goal of the iCAP is to make U of I carbon neutral by 2050.

Several strategies were presented in the iCAP to reduce greenhouse gas (GHG) emissions.  One strategy presented for GHG reduction is to educate users of variable air volume (VAV) chemical fume hoods (CFHs) on proper usage, to maximize efficiency and reduce energy demands. 

Background

A CFH is a laboratory exhaust system specially designed to contain and remove hazardous chemicals being used inside of it.  A CFH operates by taking in conditioned air from the lab room through an opening at its face and exhausting it through ducting.  U of I standards require that CFHs operate with an average face velocity of 100 linear feet per minute (lfpm) through an 18 inch-high opening.  At this face velocity and opening height, a six foot wide CFH exhausts at a flow rate of 900 cubic feet per minute (cfm).

In VAV systems, the CFH exhaust flow, general laboratory exhaust flow, and supply air flow for a laboratory are interconnected.  Closing or lowering the sash on a CFH with a VAV system can result in a reduced CFH exhaust flow and supply flow.  Several studies at other universities have demonstrated that as much as $1,800 and 3,300 pounds of carbon dioxide per CFH per year can be saved by closing or lowering sashes on VAV CFHs. However, in two studies conducted by S&C on the U of I campus, no energy savings were observed. The two studies are summarized below:   

A study of the VAV system at the Illinois Sustainable Technology Center (ISTC) in April 2009 showed that the VAV system was designed to reduce CFH exhaust flows when the sashes were shut.  This did in fact function properly, but the ventilation system compensated for the reduction in CFH exhaust flow by increasing laboratory general exhaust rate.  The result was a constant air change rate regardless of the CFH sash height, resulting in no reduction of total exhaust from the building and no reduction in energy consumption.

The Division of Safety and Compliance (S&C), with a grant from the Student Sustainability Committee (SSC), conducted a Shut the Sash Pilot Study at the Beckman Institute (Beckman) from October 2009 to February 2010.  The study was successful in changing CFHs user behaviors by encouraging the closing of CFH sashes when not in use.  However, no reduction in energy consumption was observed during the study period compared to energy usage during the same period the prior year.  Since many factors can influence energy usage, further studies need to be conducted to determine why the anticipated reduction in energy consumption did not occur.  

Recommendation

Based on these two studies it is unknown if a Shut the Sash Program would be effective in reducing energy consumption on this campus.  Systems throughout campus need to be evaluated to determine if and why they are set to function like the one at ISTC, and whether they can be changed to function more effectively in reducing building air flow rates when CFH sashes are lowered.  Also, a thorough investigation of the VAV control and sensor system at Beckman is needed to determine why the anticipated energy reduction did not occur, what repairs or modifications would be required to achieve the savings, and the feasibility of the repairs or modifications.  If it is not feasible to repair or modify the Beckman system and others on campus, then creating and distributing a campus-wide Shut the Sash Program is not feasible at this time. 

Further investigation is recommended to determine the appropriate course of action needed to design an education program. This investigation should focus on establishing a clear baseline so that reliable performance metrics may be determined and used to assess the program’s effectiveness.  The study should focus on:

1. Evaluating the VAV control and sensor system at buildings like Beckman and ISTC to determine why anticipated energy reductions were not seen.
2. Assessing the total energy consumption rates at these same buildings to determine all of the factors that affect usage.
3. Developing tested and reliable metrics from the above data that can be used to evaluate the effectiveness of any later interventions.

A Shut the Sash education program for Variable Air Volume chemical fume hood users has been shown to reduce carbon emissions and related energy costs. A well-designed educational program at this campus would require gaining a full understanding of how campus systems function, developing performance metrics for those systems, and using these data to evaluate the program’s effectiveness.