The Gap Between Building Certification and Real Performance
Posted by:
Thomas Meng
Energy Manager, Jones Lang LaSalle
We did a preliminary energy assessment last month for a site which has been managed by our IFM team for over three years. Some recommendations for potential energy savings have now been provided, but I was surprised to learn that the buildings were able to acquire LEED certification after we completed our site assessment.
To start with, inefficiencies were found in the construction and installation of the MEP systems. For the cooling water distribution system, the secondary pump’s chiller water system was designed but there is only one VFD installed for one pump, so other secondary pumps are running constantly.
We also discovered that energy waste exists on the site, caused by:
- Cooling time demand differences in different buildings, but central chilled water is supplied to all buildings including the production and office buildings. Thus, the chilled water circulation and local fans are running while the office buildings are unoccupied.
- There are big differences in delivery distance of the two chilled water loops, but with the same supply water pressure difference.
- Very low supply/return temperature differences compared with the design.
- The building automation system is installed, but its main function is monitoring and on/off control of selected units, so the main equipment is still in manual control.
- A storm water treatment system was installed for the campus, but it has never been used because of its high operation cost compared to using reclaimed water.
Better commissioning practices are important to avoid these kinds of deficiencies. Although the project may get energy savings in energy modeling (LEED points), the operating condition of the systems and equipment in the model have never existed in the actual construction of the building or the installation of the systems, and can’t even be found in the design drawings. This case goes to show that the verification process is very important for real energy savings and sustainable operations.
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