Sorry I missed this before:
mgb_phys said:
The interesting point is the complete incomprehension of people about how expensive AC is. Our company's US offices in Houston have practically no insulation, no double glazing and the inside of walls are hot to the touch. I pointed this out and was told (as if I was a moron) that they didn't need insulation because it never got cold there.
I don't know the history of building codes, but that isn't acceptable today and so buildings like that will gradually be phased-out.
For the south, heat gain through a bad wall in summer probably equals heat loss in winter, but in the north, the heat loss is much worse than the heat gain. In other words, it takes much more energy to keep a building without much interior load warm in the winter than cool in the summer. For an office, though, in the south, there is essentially no space/skin heat load. The only heat load would come from a ventilation requirement. In the north, offices still need cooling in the winter (depending on their geometry, but this is generally true), and they get that essentially free from cold outside air.
Data centres need a vast amount of cooling, for every watt of electrical power you need 3-4 Watts of AC to cool them. The cost of the actual computers is almost negligible.
A good rule of thumb is that air conditioning requires about 1.3 kW per ton for residential and light commercial A/C and 1.0 kW per ton for a high efficiency, large building system (a chilled water plant and cooling tower). In watts per watt, that's 3-3.5 kW of cooling per watt of electrical input power. So your efficiency ratio is upside-down. That's under new energy efficiency regulations, btw - two years ago, standard residential and light commercial units were 25% less efficient than they are today.
So why does air conditioning seem so much more expensive? Simple: gas and oil, which are used for heat, are far cheaper than electricity. Gas heat costs about 1/3 to 1/2 what electric heat costs, per btu or kWh. Plus, unless you have a combined energy bill, you probably aren't adding your electricity and gas together to get your real heating bill.
There are a lot of old buildings with rediculously bad energy efficiency, like the one you mention. Over the next decade or so, most of those will go away. Average commercial HVAC energy usage 10 years from now will probably be half of what it was 10 years ago, and HVAC is something like 30% of the energy usage of a commercial building.
Ironically, though, one big thing standing in the way of this is the so-called "green movement", particularly when it comes to LEED. LEED is something that building owners and architects put on advertising to say that they are being energy efficient and "sustainable", but the reality is that LEED does not require energy efficiency beyond what building codes and standards require and it promotes architectural practices that decrease building energy efficiency. But that's ok because LEED doesn't require building owners to prove their energy consumption before they mail them that pretty, platinum or gold plaque.