Environmental Engineering Reference
In-Depth Information
buildings that in the United States are collectively respon-
sible for
%
of greenhouse gas emissions. The building sector, like
transportation, uses much more energy than it needs to,
but
% of primary energy consumption, and
cult than for
transportation. Transportation is dominated by a small
number of large producers; buildings are the opposite
fixing the problem is much more dif
-
a large number of small producers. In the United States,
transportation, safety, and mileage standards are a Federal
responsibility; in buildings, construction codes and stand-
ards are mainly a state responsibility, making it
times
more dif
cult to get anything done. Only in appliances,
heating, ventilation, and air conditioning systems does the
Federal government have a say and that say has resulted in
large increases in ef
ciency.
The national stock of buildings grows slowly and turns
over slowly. Typical lifetime for building structures is
about
years, while the systems inside turn over every
years. The total net number of buildings (new minus
demolished) in the United States grows only by
%to
%
per year. To make a major impact on ef
ciency requires
not only that that new buildings be ef
cient, but also that
cost-effective retro
ts be introduced.
Total energy used in the buildings sector has been
growing faster than the population, which should be no
surprise because we use energy for many more things today
than we did
years ago. Figure
.
from the DOE
'
s
A reminder to the reader
ciency in terms of primary
energy consumption. In the building sector the biggest difference is in
the energy used to produce the electricity used in a building. On the
average only
-
I always discuss ef
% of the primary energy used to generate electricity
emerges at the wall plug.
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