CIET’s Ask Us Anything series is a free monthly Q&A session with industry experts.
The Better Building Operations session featured Michel Parent, CIET Trainer and CMVP Expert.
If you missed this Ask Us Anything, here is a key topic that was discussed during the session.
Typically in any building the low-hanging fruit, and when people think they might have optimal operation, is scheduling. I give the Recommissioning course and the BAS course, and I’ve done audits. Surprisingly, the number one measure even in old brick and beam buildings (which have usually been retrofitted with rooftop units) is to optimize the scheduling of the units.
It might sound like a no-brainer but you would be surprised how optimal scheduling is hardly ever done. I always give this example:
You get an old brick and beam building that has a VAV system rooftop unit. I’ve done a lot of audits in those buildings and I know they do sometimes have those units. Some people will start those systems 2-3 hours before occupacy and I always ask them why?
They say “we need to heat up the building in the winter time. We have to make sure the building is hot enough when people come in.”
Well VAV system is not a heating system. There is no need to start that system prior to occupancy. If your people come into the building at 8:00 AM, a VAV system in the wintertime does not need to be started before 7:30-7:45 AM.
With the pandemic, there’s a rule that there’s a mastery calculation tool that will tell you how long ahead of time you need to start it, but it’s a short period of time.
You need to know what the role of the HVACs systems are. Very often, the role of that HVAC system is ventilation and cooling, plus filtration. Usually, none of that is heating-related, so you can actually optimal start a lot of those systems way before.
If I were you, in a brick and beam building with 25 rooftop units, the first thing I would do is make sure none of them are running earlier than needed, and none of them are running later than needed. When it’s heating season, they usually do not need to run a long time, if at all, before occupancy. They need to start running early only for cooling purporses.
Second, once you’ve done that, when you’re in those old brick and beam buildings that have been retofitted with tons of rooftop units, is proper control.
You’ll see a lot of mixed up thermostats. I’ve seen so many of those where you do not know where the thermostat for a given rooftop is located. You end up with systems, different rooftop units, having the wrong set points, the wrong controls, and the wrong schedule because they are not actually controlled using a thermostat located in the zone where the diffusers are actually located. So this actually falls into recommissioning.
But in those types of buildings it’s something I’ve seen many times, unfortunately.
In those old brick and beam buildings, something you have to be very careful about is changing temperatures too much. I’m a big fan of setbacks, but brick and beam buildings can be really tricky to do a setback because they have a real hard time catching up with the temperature. I would be very careful.
It’s an easy measure to do a setback. I would do a functional test. Otherwise you may end up with a whole lot of problems rather than actual energy savings.
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