Environmental Engineering Reference
In-Depth Information
cent of the heat, because we've got to burn the energy studies somehow,
but there is no furnace.This is, of course, quite contrary to normal assump-
tions that if you have 87 100˚ days you need a furnace.The normal calcu-
lation engineers do about how thick your insulation should be compares
the extra cost of thicker insulation with the present value of the heating fuel
that you will save over time by having thicker insulation. It sounds reason-
able, except that it leaves out something rather important. How about the
capital cost of the heating system?
That isn't counted. It ought to be counted, though, because it turns out
that if you make the insulation about twice as thick and put in proper ther-
mal masses, uncoupling, air-to-air heat exchangers, and superwindows,
guess what? You don't need a furnace, with all the duct work and control
systems and fuel and power supplies, and so on, that go with it. The total
capital cost of the building goes down a little bit when you do that, because
you save more up-front getting rid of the heating system than you pay to
do so. Then we took the saved money plus some more, totaling $1.50 a
square foot after we paid for the superwindows and super insulation and so
on, and we used it to pay for things like super-efficient appliances, a refrig-
erator and freezer using 8 percent and 15 percent of the normal amount of
electricity.We could save two-thirds of what's left, but we haven't bothered
yet; and there was other stuff, day lighting and so on, that saved about 90
percent of the household electricity along with 99 percent of the water
heating energy.
All those savings paid for themselves in the first 10 months. I know that
is a long time to wait, but this is 1983 technology. Now you could do a lot
better.The household electric bill for 4,000 square feet is $5 per month.We
coined the term “negawatt” to describe such energy savings. It originally
appeared as a typo in a document, but we liked it and found it appropri-
ately descriptive, and now it is widely used.
Again, it is not a very complicated idea, but it is asking the right ques-
tion about what you are optimizing.You are not just optimizing insulation,
but rather the whole house.They have done the same trick in some houses
for Pacific Gas and Electric, in climates up to 113 or 115˚F with no cool-
ing system or heating system. The houses cost a little less to build if this is
a general practice, not a one-time experiment, and they are equally more
comfortable. In another example of the same idea, we figured out in reno-
vating a 20-year-old all-glass-and-no-windows office tower near Chicago
how you could do the normal 20-year renovation a little differently: spend
