HOBO® U12 Indoor Data Logger
Methodology
Equipment and software
- Ten Onset HOBOĻ data loggers
Each data logger collects measurements of room temperature, relative humidity, and light intensity. - Ballast detector
These handheld devices sense magnetic and electronic ballasts in fluorescent lights. Magnetic ballasts are indicated with a red light. Electronic ballasts are indicated with a green light. Electronic ballasts are more energy efficient. - Portfolio Manager
Placing the data loggers
Using a map of the middle school, we chose 30 rooms of different sizes, uses, and exposures, including classrooms, gyms, and locker rooms. We placed one data logger in each room in an inconspicuous place, such as on top of a cabinet. Because the data loggers collect temperature and light intensity, we were careful not to place them near hot objects or in dark places. We monitored ten rooms per week.
While in each room, we tested for ballast type (magnetic or electronic) using the ballast detector.
Collecting the measurements
We set up the data loggers so that they started with a button push and recorded temperature, relative humidity, and light intensity once every 30 minutes.
One or two days later, we checked the data loggers to be sure they were recording. After one week, we downloaded the measurements from the data loggers to a laptop computer, and then reset the data loggers for the next set of ten rooms.
Interviewing the building manager
We collected information about the lighting system and controls, the heating system and controls, whether or not these systems are automated, what temperatures and times the systems are set to go on and off, the gross floor area, weekly operating hours, number of students, and number of computers.
We also showed graphs of the temperature measurements to the building manager so that he could help with the interpretation.
Collecting information from staff and faculty
Using a written survey, we collected information from staff and faculty about their level of comfort in their offices or classrooms. The survey asked questions that identified when the classrooms are occupied and the level of thermal comfort experienced during those times.
Comparing energy use with other schools
We collected each school's gas and electric use for one year, along with the following information:
- Gross floor area
- Weekly operating hours
- Number of students
- Number of months in operation
- Percent of the gross floor area of the facility that is air-conditioned
- Percent of the gross floor area of the facility that is heated
- Number of personal computers
- Presence or absence of on-site cooking facilities
- Presence or absence of mechanical ventilation
We entered this information into Portfolio Manager, which generates a score. The score is a number between 1 and 100. It shows how a building's energy use compares to other buildings of similar size. For example, if your building's score is 50, it means that half of similar buildings are less energy efficient than your building and half of similar buildings are more energy efficient. If the score is 75 or more, the building is eligible for the ENERGY STAR label, a voluntary labeling program designed to identify and promote energy-efficient products and buildings.