detached, semi-detached, and terraced houses as progressively more effort
is put into patching them up. Adding loft insulation and cavity-wall insul-
ation reduces heat loss in a typical old house by about 25%. Thanks
to incidental heat gains, this 25% reduction in heat loss translates into
roughly a 40% reduction in heating consumption.
Let’s put these ideas to the test.
I introduced you to my house on page 53. Let’s pick up the story. In 2004 I
had a condensing boiler installed, replacing the old gas boiler. (Condensing
boilers use a heat-exchanger to transfer heat from the exhaust gases
to incoming air.) At the same time I removed the house’s hot-water tank
(so hot water is now made only on demand), and I put thermostats on
all the bedroom radiators. Along with the new condensing boiler came a