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Have you ever wondered why your room sometimes feels chilly in spring or why heating doesn鈥檛 kick in right away in the fall? We spoke with Director of Energy and Engineering David Osborne to find out what鈥檚 involved in the semiannual heating and cooling switchover in buildings across campus.聽

What is your basis for deciding when to switch聽from heating to cooling in the spring, and cooling to heating in the fall?聽
We determine the switchover date based on the weather forecast.鈥� We use a generally accepted industry standard approach that calls for a forecast of five days in a row with a daily median temperature of 55 degrees (that's the average of the day鈥檚 high and low temperatures).鈥犅�

We start checking the forecasts every week beginning in mid-March and mid-September and look ahead two weeks at a time.鈥疘n the mid-Atlantic region, there are some temperature spikes and dips during these periods that can cause us to make some last-minute adjustments to the switchover date.鈥疢ost years, this has resulted in our switchover beginning during the second or third week of April and second or third week of October.鈥�

What are all the considerations for when to switch over?聽
We look first and foremost at the weather forecast and how best to maintain the comfort of our faculty, staff, and students.鈥疻e know it's important to get the timing right to make the switchover because the university HVAC systems do not allow for easy reversal of our decision in the event of changing hourly or daily weather conditions. Prior to the seasonal switchover, we also ensure that appropriate time and staffing are allotted for the process, as well as allowing ample time to notify the university community.

Is the seasonal switchover process uniform across all buildings on and off campus?聽
The decision for the seasonal switchover applies to the university鈥檚 campus portfolio of 45-plus buildings on and off campus and typically begins with residence halls, followed by academic and recreational buildings. However, each building and its HVAC system is unique and requires specific steps and measures to make the switchover. While the switchover can be made to some thermostats centrally, others need to be programmed locally and manually and vary from building to building.

Why is the switchover done over a period of days, rather than simultaneously?聽
The seasonal switchover is generally done over the course of a week. It takes multiple days and a staff of up to 25 skilled and trained technicians to ensure a smooth transition, as there are multiple processes involved. Not all steps can be done in tandem or work in parallel, as certain aspects of the changeover work must be performed sequentially. Systems must be shut down in a controlled manner, configurations need to be changed, proper arrangements and safeties need to be confirmed, and systems need to be monitored and confirmed as part of critical quality control and assurance processes.聽

Is the switchover process similar to turning a switch on and off, or like a home temperature control system?聽
No. Unlike a home thermostat, our systems can鈥檛 just flip between heating and cooling depending on temperature swings. Each switchover is a large and coordinated effort involving multiple teams and thousands of different systems, some more sophisticated than others and each featuring varying levels of automation depending on their age, design, and technologies.

What are ways to improve heating and cooling residence halls?聽

• Once heating or cooling is turned on, close and latch windows to prevent drafts.聽
• Keep air vents open and ensure that vents or fan coils clear of any obstruction.聽
• If you have a thermostat, set it to 鈥渃ool鈥� or 鈥渉eat鈥� mode, as appropriate, and the fan set to 鈥渁uto.鈥澛�