Building Performance Verification
“You get what you measure” is just as true in green buildings as it is in other aspects of life. In fact, with the increased emphasis on having green buildings that actually deliver on predicted savings, Measurement and Verification (M&V) is increasingly importance. In fact, the soon-to-be-released 2009 LEED Canada NC rating system the M&V credit (EAc5) is being weighted three times more than it is now.
A very rough idea of actual building performance may be obtained by comparing utility bills to the energy costs predicted in the energy model used during building design. However, the only practical way a building owner can know if their project is living up to its potential is a comprehensive building performance program.
The measurement part of the program begins during construction when a building energy specialist installs meters on all building operating systems. These meters relay information on building energy and water use to a data storage system, usually at the location of the consultant.
The M&V consultant compiles and examines the data from the first year of building operation on a quarterly basis. The data includes the amount of energy and water consumed for each end-uses and for the total building, with the M&V consultant reviewing this information for trends which are summarized on a monthly basis. The monitored data is also compared to initial building energy models to detect problems and unnecessary energy uses as soon as possible. Solutions are then provided to the owner or other authorized party to improve building performance and reduce operating costs.
The M&V meters remain in the building so the building operator can monitor performance and operation throughout the life of the building. There are several advantages of undertaking a building performance program: predicted energy and water performance can be achieved more readily if there is quantified performance information; the meters will remain for the life of the building and can be used by building staff to ensure long-term energy accountability; corrective actions can be undertaken to correct excess energy or water usage or improve building operating conditions.
The benefits of M&V are real and quantifiable. For example, at the new Kingston Police Headquarters in Kingston, Ont., the building performance consultant installed sub-meters on energy systems which, along with BAS data, identified opportunities for increased operational efficiency and thus an additional $25,000 in energy savings per year. Another example is the performance monitoring system at the Sisters of St. Joseph Residence in London, Ont., where a thorough analysis of BAS data and heating system operation revealed that boilers were not operating at maximum efficiency. By identifying the problem, the performance consultant was able to work with the owner to achieved decreased energy use.
The graph below shows the energy performance of a five-storey speculative office building over its first year of occupancy as measured by the M&V consultant. The M&V consultant installed sub-meters on the air handling units and the lighting panel. This information, along with BAS data and feedback from the commissioning agent, allowed the M&V consultant to monitor how long and often lights and air handling were running.
For the first year, only two of the floors were occupied, yet M&V discovered that air handling units for all five floors were running (instead of being scheduled to run in “unoccupied mode”). Additionally, the occupancy sensors on the unoccupied floors were set to turn all lights on the floor on if anybody (such as a maintenance worker) entered a room and the lights did not automatically shut off when that person left. These problems account for the discrepancy between the predicted (potential) energy savings from the design energy model on the first graph point.
The lighting was corrected by the second point on the graph and by the third point the air handling unit schedule was corrected as well. In the end, conservative energy modeling meant that daylighting and occupancy sensors actually provided more savings than predicted in the energy model. In my experience, an M&V program can provide a building with up to 45 per cent energy savings per year. Given rising utility costs, these kinds of savings are hard to ignore. B