Not just Sensors and Schedules
Sunday, December 9, 2007 at 07:26PM
Toby Considine in Background, Re-thinking things

Several alert readers have observed recently that most of this is not new, that we have long known how to do this. Occupancy sensors can make the building responsive to the tenants. Operations schedules can make the building responsive to the enterprise. We’ve long had performance contractors offering to tune the building’s performance and get energy savings.

They are right. The building engineering community knows how to tune buildings and to make them responsive. Alas, the building engineering community is applying what it knows in the wrong way. It is still trying to provide an engineering service, and it continues to leave the owner and the tenant out of the conversation. It is still trying to sell the process of automating the building rather than the services that an intelligent building could provide.

Building schedules are a great place to start. Every Energy Management system offers a way for the building engineer to set whether the building is operating from 9 to 5 or from 8 to 6. They all have ways to flag holidays. But buildings aren’t operated for the engineers. The best engineers aren’t even on site as they operate multiple buildings from a distance. These operations schedules may take account of the whole building, but not the individual tenants. Because they operate as “set and forget”, they do not truly respond to needs and operations that may change every day. And so we set up building schedules to be “good enough”.

Building sensors are a great way to cover for the insensibility of the building scheduling. They work pretty well for lighting. As long as a room is almost warm enough, or almost cool enough, sensors can make a room respond fairly quickly to the needs of being occupied. Of course, it can respond so quickly by treating the room as “nearly occupied” most of the time. It can respond so quickly because the designers have over-sized the cooling equipment (often by double) just in case. Just in case what? Well, in case someone enters the room for a planned meeting and they would like to be comfortable before the meeting is over.

So there we have it. Systems that use too much energy because they are too large. Systems that are too large so they can cover for the lack of planning when the sensors only discover that the room is already occupied. Rooms that use too much energy day in and day out because they might need to respond quickly to the sensors.

Building systems that communicated with enterprise systems can anticipate scheduling needs rather than catch up to them. Freed from the need to catch up, we could size building systems properly. They would also have exactly the information they need to respond properly to Demand Response signals. If they were unable to respond, they could tell the enterprise what the scheduling constraints were that prevented the response. The enterprise, unlike the building, can decide to change the constraints.

I will write of how this lack of communication is the largest impediment to performance contracts another day.

Article originally appeared on New Daedalus (
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