temperature inside your house is a direct result of the energy
you bring in (or allow in) minus the energy you can afford to
extract, at the cost of running an air conditioner.
Did your Dad used to patrol the house, switching off any
lights he deemed unnecessary? Did this cause arguments,
accidents and disquiet among the troops? If he
prevented just five 60-W bulbs from burning one unnecessary
hour per day every day, then 108 kilowatt-hours of energy
would have been saved in a year. If we assume a cost of
$0.15 per kWh (higher in some countries, lower in others),
then your Dad would have saved the family a princely $16.20
each and every year! Almost enough for two serves of
Today, most of Australia has converted to Compact
Fluorescent bulbs. The same regime of
light-switching-off would now save a barely-discernable $3.24
per year on energy costs mounting to $1000 to $3000
annually. Switching to compact fluorescents saves the
average household from $50 to $100 per year in lighting costs,
but also saves some of the costs of cooling during the
An incandescent bulb creates visible light by electrically
heating a fine wire element to a temperature between 2000 C
and 3000 C. Only around 2% of the energy consumed comes
out as visible light, leaving ample room for
improvement. The rest becomes heat, which you in effect
have to pay for twice. Your air conditioner has to do
extra work to remove that unwanted heat.
Compact fluorescent bulbs are close to 10% efficient, as
well as lasting 5 to 10 times longer. They reduce your
summer energy bills both directly and indirectly while making
life more comfortable, by putting out around 80% less heat.
Incidentally, the incandescent light bulb was invented not
by Thomas Edison in 1870, but by Sir Humphrey Davy in
1802. Edison's contribution is summed up by his
statement, "We'll make electric lighting so cheap that only
rich people will burn candles." This he did. Now
with compact fluorescent lighting, and very soon with LED
lighting, it hardly matters whether you leave the lights on or
Far more important for keeping cool in summer is the energy
coming in from outside. The following steps will help keep you
Insulate. Heat always flows from high temperatures to
low temperatures, but it doesn't have to do so very
fast. Light, porous materials are poor conductors of
heat; while hard, dense or crystalline materials are
excellent heat conductors. Therefore brick, cement,
metal and glass walls will make your house hot; while
fibreglass batts, rigid foam, enclosed air gaps, and wood can
help you keep cooler longer.
Ventilate. Hot air rises naturally, so let it.
Allow the air at the highest points in your house to ventilate
upwards and outwards. Ventilate the attic space
aggressively and thoroughly, too, since it can be 10 C to
20 C hotter in there than outside.
Double Glazing. I would never build or renovate a
house without insisting on double-glazing. Anything less
is a complete and utter waste of your time and
money. It dramatically reduces incoming heat in the
summer, heat lost in the winter, and very importantly, it
vastly reduces the noise you can hear from outside. Once
you've lived in a double-glazed house, you will never want to
go backwards. I would go so far as to say this should
become mandatory in the building code. It is that
important, that effective, and it doesn't have to be much more
expensive once manufacturers get on board.
Shade. The less sunlight your house soaks up, the
cooler you will stay and the less money you will spend on
cooling. Shade the house and the perimeter of the
house to a distance of 3 meters. Eaves are a must;
verandas are even better. Place garages, patios, sheds
and carports on the sunny sides of the house and make them
taller than you first intended.
Also, reflective roof and wall paint is very
effective. Engineered paints can reject up to 80% of the
sun's rays, but some built-up neigbourhoods do not allow
them. They are blindingly white to look at.
If you are sweltering in the southern hemisphere's summer,
consider implementing some of these tips.