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Q & A
- Why doesn’t setting the thermostat really high or low make the room warm up or cool down faster?
Room-level HVAC controls continuously operate to maintain the room thermostat setpoint. The system controls do not look at the difference between room temperature and thermostat setpoint. Instead, the system controls operate in two modes: setpoint satisfied or setpoint not satisfied. When the system setpoint is not satisfied, the controls modulate to add more cold air or warm air to drive the room toward the setpoint. The system will continue to modulate until the setpoint is reached.
Setting the thermostat really high or really low typically results in the room overshooting the desired temperature. It is recommended that room thermostats be set between 68°F and 76°F. When a room feels uncomfortable, adjust the thermostat in small (1° or 2°) increments.
- Is opening the windows more or less energy efficient than the HVAC?
Having windows open is almost always less efficient than the HVAC. The university HVAC systems filter, dehumidify, and temper outside air provided to the building spaces. Opening the window allows unconditioned outside air in and can work against the HVAC. Even if the temperature outside feels right, it still needs to be filtered and/or dehumidified, causing the HVAC system to work harder to compensate. An open window can also allow pests like insects and mice into the building.
If your space feels uncomfortable and is not maintaining the room thermostat setpoint (plus or minus more than 2 degrees), the HVAC system may need repair. Notify your facility manager or contact Facilities Service Center (734-647-2059 or FO-Service-Center@umich.edu) to have the issue addressed.
- How are office thermostats different from your system at home?
Your home furnace operates intermittently and turns on when the temperature in the home is a degree or two away from its thermostat dial setpoint. The furnace operates in either heating or cooling mode to satisfy the home’s thermostat setpoint.
The Heating Ventilation and Air Conditioning (HVAC) system at the university operates continuously, providing filtered, dehumidified, and tempered air (typically near 55°F) to building spaces. Then, the individual room thermostat operates to modulate the amount of air and any additional heat that maybe required to maintain the room thermostat setpoint (typically near 72°F).
Why supply 55°F air year-round?
Commercial HVAC systems typically supply 55°F air throughout a building year-round to maintain the capability to provide cooling. Believe it or not, most commercial buildings have a need for cooling year-round. From computer labs and server rooms to highly occupied spaces, buildings need cool 55°F air to offset internal heat sources.
In areas of the building that generate little heat, like an office, the HAreVAC system supplies the minimum required air to meet code requirements and when necessary adds heat to satisfy the room thermostat setpoint.
- How do I set my blinds to keep heat out during summer and retain heat during winter?
You can use blinds to keep your space more comfortable and conserve energy. In the summer, completely lower the blinds then adjust the slats to allow for the desired amount of natural light. The more the blinds are closed, the better they are at reducing the solar heat gain because they reflect some of the solar radiation (heat) away from the room.
In the winter, open the blinds on southern facing windows to allow the solar radiation to enter the space, helping to keep the space warm. When the sun is down, keeping the blinds closed creates an extra barrier that helps keep heat in. To retain even more heat, close curtains or drapes in the winter.
Learn more at energy.gov/energysaver/energy-efficient-window-treatments.
- Should I let automatic lights turn off on their own or turn off the lights manually?
Lighting occupancy sensors are great at acting as our steward when we forget to turn off the lights. However, it is best to turn off the lights yourself. Otherwise they will stay on for 20-30 minutes after everyone leaves.
Some lighting controls have an auto-on feature as a convenience. You may wonder: will turning off the light screw up the auto-on feature when someone reenters the room? The worst that can happen is that turning off the light temporarily disables auto-on. The next occupant would need to switch on the light manually, which re-enables the auto-on feature. When in doubt, turn the light out!
The lights keep turning off while I’m still here!
Occupancy sensors use infrared and/or ultrasonic sensors to detect whether someone is present. If the sensor’s field of view is not calibrated to cover the entire space, the sensor may not register that someone is in the space and will therefore turn off the lights. The sensor may have failed or may need to be calibrated. If you experience a problem with your lighting controls, please notify your facility manager or contact Facilities Service Center (734-647-2059 or FO-Service-Center@umich.edu) to have the issue addressed.
- Why are fume hoods so energy intensive? And how can I reduce how much energy they use?
Fume hoods continually exhaust room air to remove any hazardous chemicals from the hood, keeping occupants safe. To maintain the proper room pressurization, outside air is conditioned (filtered, dehumidified, cooled or heated) and continually supplied to the entire space to offset the air that is being exhausted by fume hoods. The continuous exchange of air is energy intensive because the HVAC system must run continuously.
Most fume hoods exhaust more air when the sash is fully open, which means the room requires more conditioned air to offset the exhaust. Therefore, keeping the fume hood sash closed when not in use reduces energy use.
Note: energy use varies by fume hood type. Bypass fume hoods consume energy at a near-constant rate, regardless of sash position. Even though closing the sash on a bypass hood doesn’t save energy, for safety it’s always wise to keep the sash closed when not in use.
- How is water conservation related to energy conservation?
Water usage has a direct impact on energy consumption because energy is required to treat and distribute water. By reducing water usage, water distribution systems can treat and pump less water. Conserve water to conserve energy!