It is common for new construction projects to be designed to meet the original design intent, while energy consumption is often overlooked and left out of the design specifications entirely. Reviewing existing mechanical system operations is critical to optimizing building energy efficiency. In 2009, the LISE laboratory building was the second largest GHG emitter on the FAS campus in terms of absolute emissions and third highest in terms of its GHG intensity by square foot.
Thanks to the retro-commissioning effort that the FAS facilities team launched, various existing building systems that serve a common 9,600 square foot clean room, were able to be combined into a more “closed loop” controlled feedback approach. The building automation system (BAS) was further optimized to share common data amongst the systems.
The systems are all intelligently linked and share data through the BAS and their associated software programs. Together, they reference both the ever changing outside air dew point, as well as monitoring the space conditions and their associated requirements. Simultaneous heating and cooling is now prevented, which in turn helped humidity and overall control of the clean room itself. Additional energy consumption was reduced by sharing key data between the re-circulation air handling units and primary air handling systems. This data allows the systems to anticipate and react to the outside air conditions (outside air dew point temperature) while more accurately maintaining the space conditions. Finally the total air changes to the space were able to be reduced by controlling to maintain a slightly positive pressure within the clean room. This allows the primary air and exhaust air duct pressure to be reset accordingly to the pressure changes within the space served. Many “blast gates” that were installed for future expansion were not being used and were now able to be closed. This changed the space differential and in turn, allowed the exhaust air systems and primary air handler system fans to ramp down in response.
By allowing the discharge air temperature to be reset to as high as 70 degrees F when outside air conditions permit (sensible cooling requirement only), pre-heating, pre-cooling, humidification and dehumidification cooling sections receive less of an overall load and provide an added energy savings benefit. This measure not only takes advantage of the many periods throughout the year where de-humidification is not needed and allows for a reduction in cooling/reheating energy, but also provides a system that maintains consistent space conditions and ultimately responds quickly to outdoor weather changes.
Creativity and Innovation
This project is a great example of challenging the original design parameters and reducing energy consumption without any major and costly infrastructure upgrades.
The success came in many small and unglamorous steps that were made possible by the trust of senior administrators. What has been achieved at LISE could not have happened without the support and cooperation of all its occupants.
- Senior Facilities Manager Thomas Tribble
Scale of Impact
- $3.15 million in savings since 2009.
- CO2 emissions reduced by 7,421 MTCDE since 2009.
- The facilities team monitors more than 3,400 data points from equipment such as air handling units, and chilled- and hot-water pumps.
- Reductions in airflow have had the greatest impact.
Jason Hehlo, FAS Energy Manager, reviewed and re-wrote the control programming after identifying several opportunities for improvements in efficiency. This accomplished similar objectives with respect to heating, cooling, humidification, de-humidification and air exchange. Jason’s observations were verified by Craig Rochester of Cimetrics’ continuous commission software and Mike Beauvais of Siemens. Tom Tribble, Senior Facilities Manager was able to work with the Faculty and Clean Room staff to help implement changes in control methodology.