What are the factors that affect building energy use?
We'll take a look at three:
Outside Air Temperature
Buildings can be used for a variety of functions: administrative offices, faculty offices, classrooms, laboratories for research and classes, food services, conference rooms, study areas and on and on.
We’ve grouped these uses into five categories that we call classrooms, laboratories, housing, community, and offices. Each category has a unique energy profile.
For example, laboratory spaces use a lot of energy because they require much higher ventilation rates, as the air cannot be recirculated in a lab. The air coming into a lab must be 100% outside air (not recirculated), and then it must completely leave the building through the exhaust systems. Moving this quantity of air with fans, and heating and cooling the air, is an energy intensive process.
Check out all of the different building types on the Campus Energy Education Dashboard.
How does the weather affect how a building uses energy?
Lets look at the steam and chilled water usage.
No matter what type of building you look at, you'll see that chilled water is highest when it’s warmer outside, and that steam is highest when it's colder outside.
January usage: 319,189 kBtu
July usage: 36,225 kBtu
Steam is highest when it’s colder outside.
This is because more steam is required to heat the buildings during the colder months of the year.
Inversely, during the summer months, you'll see chilled water reach its peak usage because the buildings need that precious cooling power.
January usage: 56,225 kBtu
July usage: 458,907 kBtu
Chilled Water is highest when it's warmer outside
What about the people in the building? They must affect a building's energy use intensity.
Indeed; people do have the largest impact on the lighting and plug loads of a building.
People also affect the Heating, Ventilation, and Air Conditioning (HVAC) system based on when the system is scheduled to be on and off. For example, the HVAC schedule needs to be properly tuned to the hours when the building is occupied. If it’s not, there is potential energy being wasted and/or uncomfortable people.
Occupancy in a Giedt Classroom
In the graph below you can see how the energy demand tracks with the classroom's occupancy.