Downlights are lights recessed into the ceiling and are common in many homes built in the 1980s and 90s. As these lights have transformers in the ceiling that get hot, they require 100mm of clearance between the light fitting and any insulation, which leaves large gaps in the ceiling insulation. As typically a ceiling has multiple of these lights, the effectiveness of any ceiling insulation with older downlights is greatly reduced.
Another problem is that 95% of the power these downlights use is converted to heat, not light. Many of these lights have a gap between the bulb and the ceiling meaning that hot air flows freely through to the ceiling space, reducing the warmth of your home. We strongly recommend replacing any old-style downlights, especially if you are getting insulation installed.