How does a green building maintain its energy savings over the long haul? This is one of the critical questions in green building design, since there is plenty of evidence that building energy performance degrades over time. Systems wear out, and new building maintenance and operations people may fail to make necessary repairs, carry out preventive maintenance and generally fail to manage the building's energy-using systems as originally designed.
Green buildings are encouraged by LEED to take two simple measures to counteract this tendency toward energy-efficiency degradation. First, projects can gain a LEED point by developing a monitoring and verification plan, following established international protocols and then installing sensors that measure the actual performance of key energy-using systems such as chillers and boilers. The sensors are connected to the building automation system and provide information that allows engineers and building operators to pinpoint problem areas and fix them. Creating the plan and installing extra sensors are not that costly, typically $30,000 to $50,000, which is barely more than pocket change for a large office or residential building.
Additionally, building owners are encouraged to document systems training so that future operators can learn proper use and maintenance of the systems. The LEED for Existing Buildings standard encourages buildings to be re-commissioned every five years, so that energy performance can be maintained over the building's lifetime. For most institutional building owners, this is a smart thing to do since they're paying the bills.
The leading force in the US behind measurement and verification is the Federal Energy Management Program, which developed the International Performance Measurement and Verification Protocol, to identify and codify best practices techniques for verifying the energy performance of new buildings.
Think for a moment of the simple task of comparing this year's utility bill to last year's to determine if you're using more or less energy. What could affect the outcome? Weather is certainly a major variable: was this year colder or hotter than last year? Did the use of the building change, so that there were more or fewer occupants? Did the hours/days the building was occupied change significantly (for example, did someone put on a second shift)? Did someone put in a data center that uses a lot of power for servers, generating also a lot more waste heat that increased cooling demand? What about changes in lighting levels, occupancy sensors, ventilation levels and set-point temperatures for heating and cooling? Was preventive and remedial maintenance carried out? Were portions of the building vacant for any substantial period? How would you determine all this without a good plan and enough measuring and monitoring points to get accurate information? You can see the wisdom of planning ahead by following the LEED protocol for creating a plan, installing enough sensors and then collecting the data.
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