Green Campus Building Services - Existing Buildings
Building Energy: Background
Energy is used by buildings in many different ways throughout the life of a building. Even before a building is occupied, significant energy has been spent during both the building's construction and in the manufacturing of materials that make up the building. Once operating, buildings import electricity, natural gas, steam from the Blackstone Steam Plant, fuel oils, ground source heat, and centrally produced chilled water to meet the heating and cooling requirements throughout the year. Each of these utilities uses a particular unit to describe the amount of energy being delivered. As a result, facility managers are required to understand the difference between kilowatts, kilowatt hours, MMBTU, therms, barrels, and ton-days, and also how much of each utility should used in each building. One of the strategies that the Green Campus Building Services promotes is to combine all energy used in a building into a single unit called KBTU (1000 British Thermal Units). This is quickly becoming a standard across the building energy industry in the US.
It is important to remember a few things when talking about energy and buildings. First, water is not usually thought of as a unit of energy, but rather a unit of volume, typically hundreds of cubic feet (ccf). This means that water can not be added to total KBTU when describing building performance. This distinction is quite important, since water conservation is a fundamental component of high performance buildings and should not be overlooked. In addition, many water conservation projects offer significant savings to investment ratios. Second, when we measure energy used in a building, we actually are measuring how much energy is consumed at the site during a particular time. This end use is quite different from the amount of energy burned at the power plant, because significant energy is also consumed during processing and transportation of fuel. This is especially relevant to electricity consumption, where only one third of the primary energy used to create electricity is actually consumed in the end use buildings.
How efficient are buildings at Harvard?
Determining how efficient a building is operating can be quite complex. GCBS recommends an approach which uses the most accurate data available to develop a performance baseline. This baseline can be used to continuously monitor energy consumption every month and track the effects of repairs, upgrades and other efficiency measures.
In addition to baselines, each building should calculate its energy performance based on KBTU per square foot. This metric allows managers and operators to compare the performance of multiple buildings. Using KBTU per square foot, an Energy Utility Index can be established to rank a building's performance, as compared to other Harvard properties or compared to the national average. When possible, GCBS uses the EPA Portfolio Manager to generate the performance rating. For buildings considering LEED for Existing Buildings, a building energy rating of at least 67 is required as a prerequisite for energy performance.
The Green Campus Building Services is currently compiling building performance data for many properties across Harvard. Check back soon for an update.