Australian homes are notoriously cold in winter — draughty, with poor insulation, thin glass and inadequate heating. But there’s a growing movement of people retrofitting their homes to make them cheaper to run and more comfortable year-round, while also reducing emissions.
Another thing to try for windows is to make a second layer for the window frame out of flyscreen moulding and some clear plastic. It’s a more expensive method than bubble wrap but looks better and has the benefit of being able to see through it easily. I haven’t really quantified how much of an effect this makes but with the windows I did this for there was a noticeable decrease in condensation on the glass so there is definitely some reduction in thermal transfer.
You can buy the aluminium profile, corner joiners, and matching rubber stripping used for making flyscreens in a hardware shop, as well as clear plastic in rolls (or lengths thereof). With this you make a frame that snugly fits into the window surround - ideally placing the plastic within a cm or so of the glass. You’ll need a hacksaw or something else to cut the aluminium, ideally a combination square to help with marking 45 degree angles, and I did find the little roller tool sold to help insert the stripping was useful.