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Old 07-18-2016, 09:09 AM
MacLir MacLir is offline
Join Date: Mar 2010
Posts: 598
Originally Posted by Orwell View Post
The "wasted" energy in any type of lighting is thrown off as heat. And, certainly, leaving lights on in the winter adds heat to the building, which can be viewed as a benefit. While some of the heat radiates downward to the occupied space, some of it goes up above the drywall or suspended ceiling and does not benefit occupants. But, certainly, leaving lights on during the heating season is better than leaving them on during the cooling season, where the wasted heat has to be removed by air conditioning.

If your building is actually dependent on byproduct heat from lighting, it sounds like the heating system is undersized. I can't imagine it makes sense to keep incandescent lights for the byproduct heat, since HVAC systems are more efficient at heating space than lights, but it is certainly a short-term strategy. If you are using incandescent lights, you are likely either wasting light or wasting heat, depending on the weather and time-of-day occupancy.
Notwithstanding all this, which I was aware of, I think the theory is that the lights will be turned on anyway during occupancy, and the waste heat needs to be factored in (and they do get hot - they are mostly HID or something like). Since it's factored into the heat balance for day, it follows to use the heat at night (seasonal? I don't know) rather than increase the size of the building heaters for peak load. Again, I don't know why it was done that way, but it is what it is, and an engineer who was supposed to know what he or she was doing designed it that way.