Adjusting operations for the winter months is important for two reasons:
When the building is unoccupied, set the thermostat about 8-10 degrees lower than the occupied temperature. If using more advanced strategies with occupancy sensors, you may consider three different settings:
1. What is the sequence-of-operation for your nighttime setback?
3. Is your nighttime setback temperature suitable for a proper building recovery?
The winter months demand a delicate balance between cutting energy costs and avoiding frozen pipes, which would be a much bigger and more expensive problem. With a well-planned energy reduction strategy, building operators can drop their consumption while incorporating freeze protection.
In the image below, you can see a chart of a building’s kW consumption (green line) over the course of a week last January. If you look by the arrows over Monday and Tuesday, you will notice the building’s energy consumption did not return to baseload (in this example, about 250-300 kW) on Monday night. Why?
Well, if you look at the temperature (blue dotted line), you’ll see that it was actually expected to drop from 40 degrees on Monday to 3 degrees on Tuesday!
Many building engineers will decide to run buildings at night before a cold day, especially when it’s the first shock of the season. However, this decision must be made on a case-by-case basis.
Dunfee explains, “Some buildings have trouble heating on colder winter days, especially when temperatures drop into the 20s for a daytime high. As soon as you reach temperature extremes, building operators often start thinking about operating their buildings overnight.”
Although ventilation requirements seem counterproductive to efficient operations, there are ways to optimally schedule operations to prevent wasted energy.
Dunfee suggests delaying the start of your ventilation with an economizer during the building’s warm-up recovery time. No occupants in the building means no one will notice the cold air entering the building – instead, tenants will just enjoy the refreshing, crisp air you let in before their arrival. Ventilating the building while starting it up simultaneously will waste a significant amount of energy because the heating system is fighting the outside elements. Plus, the building will take much longer to reach its ideal temperature. Sometimes, it’s actually better to start your building a few hours early, so it can completely warm up before you start introducing outside air into the building, making it easier for the building to recover.
Each building varies greatly, so strategic winter operations must consider the individual building’s needs. However, you can certainly investigate what your ventilation schedules are, why they work that way, and how you can adjust your operations for optimal winter efficiency.
Want to quickly pass these tips along to your team? Start the conversation by asking them these questions:
1. Is your building’s HVAC system ready for winter operations? Does it need to be tested and calibrated before the winter?
2. What is nighttime setback schedule? Has this strategy been optimized for winter?
3. Is your building prepared for freeze protection?