Prepare Your Buildings for Winter: Nighttime Setbacks, Freeze Protection, and Ventilation Schedules November 4, 2014 | Samantha Dubrow

Featuring insights from Lee Dunfee, Cassidy Turley’s Senior Vice President of Engineering Operations.
 
It’s the first week of November, but it sure doesn’t feel like it. Last week it was 80 degrees in DC, and this week it’s been in the mid 60s. This abnormality makes it challenging to decide when to switch over to winter building operating schedules. However, it does give a few extra weeks to make sure you’re fully prepared to work efficiently this winter.

Winter operating schedules are important for two reasons.

1. There is a lot of extra waste to be avoided during the winter.

2. Many property managers and building engineers often don’t focus enough attention in a few key areas.

 

Oftentimes, when buildings are acquired from previous owners, the new owners are not made aware of many building functions. Below are the most important things for you to consider so you can keep your buildings operating smoothly and at maximum performance.

1. Nighttime Setbacks

In an interview with our good friend Lee Dunfee, Cassidy Turley’s Senior VP of Engineering Operations, he explained that less than 50% of the people he talks to about building operations can give him an accurate answer about how their nighttime setbacks function. Dunfee emphasized that this is one of the most important thing to think about going into the winter months.
First, you need to ask yourself how long your building takes to recover in the morning. This is a bit different for every building, depending on system type, age, and use. Not only do you need to consider how long it will take to reheat the air, but you also need to think about how low you want the inside temperature to get, considering how long it will take to make sure that desks, chairs, and filing cabinets aren’t freezing when tenants arrive at work.
Dunfee’s suggestion is to set your unoccupied temperature about 8-10 degrees lower than the occupied temperature. If you are using more advanced strategies with occupancy sensors, you may consider three different settings:

 

1. an occupied setting, let’s say at 72 degrees,

2. an unoccupied setting based on information from the sensors, at 69 degrees,

3. and then a nighttime temperature, at 64 degrees.

 

It is important to understand your building’s nighttime setback strategy at the beginning of the winter, preparing for what will come. A few things to consider:

 

1. What is the sequence-of-operation for your nighttime setback?
2. Has your team tested the function of the nighttime setback and confirmed it is operating properly?
3. Is your nighttime setback temperature suitable for a proper building recovery?

 

There is an important balance to “strike” and nighttime setbacks, considering efficiency, occupant comfort, and freeze protection.

 

2. Freeze Protection 

The winter months demand a delicate balance between cutting energy costs and avoiding freezing pipes, which would be a much more drastic and expensive problem. 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 a Monday and Tuesday, you will notice the building did not return to its baseload Monday night. Why did this happen?
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 all the way to 3 degrees on Tuesday!
WinterBuildingSchedule

 

Many building engineers will make the decision to keep their buildings running at night before a cold day, especially when it’s the first shock of the season. Once again, whether or not this is the best decision varies from building to building.

 

During the interview, Dunfee explained, “Some buildings have trouble heating on colder winter days, especially when DC temperatures drop into the 20s for a daytime high. As soon as you reach temperature extremes, building operators often start thinking about operating their building overnight.”

 

When asking yourself whether to keep your building running into the night, you’re considering both freeze protection and tenant comfort. It’s fine to raise the temperature a few degrees for the first few cold days, but as people become acclimated to the colder weather, you should try to take the building back to its normal temperature. Shared spaces, such as vestibular areas and lobbies, loading docks, stairwells, etc. do not need to be excessively heated during the winter, and readjusting the temperature is a great way to avoid excessive costs in non-tenant spaces.

 

3. Building Ventilation Schedules

Every building has ventilation requirements, but there are ways to meet those requirements without wasting energy, which is especially important during the winter.

Dunfee’s suggestion is that you should consider delaying the start of your ventilation during the building’s warm-up recovery time, since there are no occupants in the building. If you do start heating the building and add outside ventilation at the same time, you could be wasting energy, and it will take much longer to bring your building to its perfect temperature.

For example, if you start your building 3.5 hours before tenants arrive, you don’t need to be ventilating the building when you first start it. 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 much easier for the building to recover. Once again, this differs a bit in every building, but you should certainly ask yourself what your ventilation schedules are, why they work that way, and if your current schedule will be the best option for the winter.

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 does your nighttime setback schedule look like? Why? Is it optimized for winter?

3. Is your building prepared for freeze protection?

 

4. When is your building being ventilated? Why? Is the schedule optimized for the cold months ahead?
 

Do you have other best practices to share? We’d love to hear about them! Please leave a note in the comments section below.
 
Building Engineering, Energy Efficiency, Tenant Satisfaction

About The Author

When Samantha isn’t writing for the blog or managing our HR like a champ, she studies Organizational Psychology at George Washington University.