book titles,” and you’ll have bright lights on all the time. But that question
presumes that we have to fix the light level; and we don’t have to. We can
fit light switches that the reader can turn on, and that switch themselves
off again after an appropriate time. Similarly, thermostats don’t need to be
left up at 20 °C all the time.
Before leaving the topic of thermostat settings, I should mention air-
conditioning. Doesn’t it drive you crazy to go into a building in summer
where the thermostat of the air-conditioning is set to 18 °C? These loony
building managers are subjecting everyone to temperatures that in winter-
time they would whinge are too cold! In Japan, the government’s “Cool-
Biz” guidelines recommend that air-conditioning be set to 28 °C (82 F).
If you get the chance to build a new building then there are lots of ways to
ensure its heating consumption is much smaller than that of an old building.
Figure 21.2 gave evidence that modern houses are built to much better
insulation standards than those of the 1940s. But the building standards
in Britain could be still better, as Chapter E discusses. The three key ideas
for the best results are: (1) have really thick insulation in floors, walls, and
roofs; (2) ensure the building is completely sealed and use active ventilation
to introduce fresh air and remove stale and humid air, with heat
exchangers passively recovering much of the heat from the removed air;
(3) design the building to exploit sunshine as much as possible.
So far, this chapter has focused on temperature control and leakiness. Now
we turn to the third factor in the equation:
|average temperature difference × leakiness of building
|efficiency of heating system
How efficiently can heat be produced? Can we obtain heat on the cheap?
Today, building-heating in Britain is primarily delivered by burning a fossil
fuel, natural gas, in boilers with efficiencies of 78%–90%. Can we get off
fossil fuels at the same time as making building-heating more efficient?
One technology that is held up as an answer to Britain’s heating problem
is called “combined heat and power” (CHP), or its cousin, “micro-
CHP.” I will explain combined heat and power now, but I’ve come to the
conclusion that it’s a bad idea, because there’s a better technology for heat-
ing, called heat pumps, which I’ll describe in a few pages.