"Down, down, down with halogen down lights!" is my new mantra. "Don't do it!" I yell passionately in my energy auditing nightmares.
Quite simpy, halogen downlights are a disaster when it comes to energy efficiency, for the following reasons:
1. they are energy guzzlers
2. they create gaps in your insulation, reducing thermal efficiency dramatically
3. they get hot and so make their own little convection current which sucks the warm air, that rises to the ceiling, up into the roof space... making the pressure difference (or stack effect) in the room greater and drawing more cold air in from the cracks and gaps near your floor. Goodbye heated air, goodbye comfort and ooroo money!
When we run an air leakage assessment, standing beneath a downlight is like standing beneath a small ceiling fan, as air rushes in from the roof space. The thermal image above is of a downlight (not switched on) while we are depressurising the house - the rays of yellow are caused by the warm air from the roof space being drawn in around the edges of the unsealed and uninsulated, hot, energy guzzling downlight! Imagine the opposite happening in winter as you spend your precious pennies trying to keep your house warm... because that is exactly what happens :-(
A couple of other good reasons to avoid downlights:
a. they make gaps in the ceiling through which insulation fibres, dust, dirt and pollutants can drift into the house
b. they are a fire hazard
Read a more thorough analysis by Four Corners' reporter Jonathan Holmes and check out the options for making the best of a bad bunch if you're stuck in a house with lots of standard halogen downlights. There are several places online where you can check out more energy efficient downlight options and downlight covers that reduce the gaps in your insulation and the risk of fire.