Operating Energy In Buildings

The operating energy of a building is “the amount of energy that is consumed by a building to satisfy the demand for heating, cooling, ventilation, lighting, equipment, and appliances” (Canadian Architect). Operating energy is a convenient way to compare the energy consumption of different building systems, as it’s independent of the materials used. Instead, operating energy deals with the amount of renewable or non-renewable energy required to maintain the building functions and occupant activities.

There are two forms of energy: non-renewable (e.g. coal, oil, natural gas, etc.) and renewable (e.g. solar, wind, water, etc.). Today, most buildings around the world depend heavily on the use of non-renewable energy.

Energy consumption data is expressed in terms of joules (J). But often with extremely high quantities of energy, it’s more convenient to use Petajoules (PJ). One PJ is equivalent to 1 x 1015 joules. One PJ of energy is enough to meet the energy demands of about 8,900 Canadian households for one year (Natural Resources Canada, 2008).

The Office of Energy Efficiency, Natural Resources Canada distinguishes between two types of energy use:

Primary Energy Use: “Represents the total requirement for all uses of energy, including energy used by the final consumer (see Secondary energy use), non-energy uses, intermediate uses of energy, energy in transforming one energy form to another (e.g. coal to electricity), and energy used by suppliers in providing energy to the market (e.g. pipeline fuel)”.

Secondary Energy Use: “Energy used by final consumers for residential, agricultural, commercial, industrial, and transportation purposes”. In terms of the Building sector, Secondary Energy Use refers to the energy used for space heating and cooling, lighting, running appliances, etc. It does not include energy generation or transportation and is only concerned with final end use on site.

"The operating energy of a building is 'the amount of energy that is consumed by a building to satisfy the demand for heating, cooling, ventilation, lighting, equipment, and appliances'..."

In Canada, buildings consume large quantities of energy. Buildings consume both embodied energy in the materials that they use as well as operating energy to maintain various functions. Plotting the results of the Secondary Energy Use from the Energy Use Data Handbook Tables provided by the Office of Energy Efficiency, Natural Resources Canada, some interesting observations can be made (Figure 4).

Figure 4: Total Secondary Energy Use by Sector in Canada (2006) (Natural Resources Canada, Office of Energy Efficiency, 2006).

Building sectors around the world are significant consumers of energy. The Building sector, which combines Residential and Commercial/Institutional sectors, consumes approximately the same quantity of energy as the Transportation sector yearly. Roughly one third of Canada’s Secondary Energy consumption is due to the operation of buildings.

Residential buildings refer to single and multi-family dwellings, which include both low and high-rise buildings, while Commercial/Institutional buildings include offices, hospitals, factories, shopping centers, recreational facilities, schools, hotels, and more.

Secondary Energy consumption, also known as the operating energy, is quite significant in Commercial/Institutional buildings. Figure 5 indicates that space conditioning (space heating + space cooling) accounts for nearly two-thirds of the total operating energy of a Commercial/Institutional building. As well, auxiliary equipment and motors require nearly 25% of the operating energy and lighting demands tend to require about 11%. Finally, water heating demands completed the energy profile, requiring only 9% of the total operational energy. Similar to Residential buildings, statistics for Commercial/Institutional buildings cover a broad range of building types, from old brick structures with little insulation to today’s cutting-edge energy efficient buildings.

Figure 5: Total Commercial/Institutional Secondary Energy Use by End Use in Canada (2006) (Natural Resources Canada, Office of Energy Efficiency, 2006).

The energy use data for Commercial/Institutional buildings from Natural Resources Canada can be further sub-divided based on Activity Type. When the Secondary Energy Use in Commercial/Institutional buildings is plotted it’s noted that approximately 35% of the total Secondary Energy Use in this sector is a result of Office buildings. Retail and Educational Services buildings account for about 17% and 14% of the Secondary Energy Use respectively. Combined, these building types (Office, Retail, and Educational Services) account for almost 66% of the total Secondary Energy Use.

Figure 6: Total Commercial/Institutional Secondary Energy Use by Activity Type in Canada (2006) (Natural Resources Canada, Office of Energy Efficiency, 2006).