So, here’s the tangential question: In this building, a quick look at the ceiling shows there are 1080 standard 4-foot, 32-watt fluorescent tubes in standard drop-ceiling troffers with cracked-ice diffuser panels, providing general lighting over the cubes. That comes to nearly 35 kilowatts of electrical power consumed, per floor, for general lighting.
What percentage of that 35,000 watts is wasted as heat?
All of it. Even the light is converted to heat as its absorbed by the walls, floor, ceilings, etc., minus what amount manages to escape through the windows.
That’s a bit more, ahhh, thermodynamic than I was expecting. 
I was thinking more along the lines of:
Electricity goes into fixture. Fixture makes a bunch of light and some amount of heat from inefficiencies in the ballast, wiring and the fluorescent tubes themselves. How much of the input power is wasted in that way?
That’s true, much of the HVAC system is to move air around to stabilize the temp all around the Mall.
Being Minnesota, for much of the year they don’t really need to run Air Conditioners for cooling – they can get cold (even frigid) air by just pulling it in from outside. But such air is extremely dry. To get the humidity of that air into the human comfort area, they have to add water to it. The HVAC system has large humidifiers for this purpose.
During the summer, they have an equal or bigger problem reducing the humidity of the air; this is a big part of the job of the Air Conditioners.
I believe the Mall actually does have a heating component (furnace) in the HVAC machinery. But it is quite small in relation to the building size, really only for supplemental heat when/where needed. It would not be enough to keep the Mall heated on its’ own.
And it stays warm because it doesn’t really shut down very long. The entertainment parts (bars, movies, restaurants) are open till about 1AM. Then there is a major transit station underneath the Mall, with associated coffee shops & similar restaurants, that starts getting active about 6AM or so. And the 5 hours in between are when much of the cleaning & such is done.
The old Kansas City, MO, Plaza Library was heated only with the lighting. The south side of the building was all windows, and the lights were left on all day, and that was all it needed. Of course now it’s been torn down, and while the new library also has a lot of south facing windows, I don’t know if it has heat or not.
A fluorescent light might waste about 50% more power than is put out as light. For example, here’s a typical ballast datasheet (warning - PDF). The 40 watt lamp ballast actually consumes 58 watts, of which 40 makes it to the lamp. The other 18 are lost as heat in the ballast. This is 58/40 = 145% more power than the lamp wattage itself.
That turns your 35kW in the example you mentioned into 50kW.
Arjuna34