I live in a 2 storey apartment in Auckland CBD. I'm on the top floor of the building. I have insulation in the ceiling above me, insulation below, none in the walls. I only have 1 wall that faces the outside - this has some large windows / slider door for balcony in it as the room that faces the outside is 5.8m high.

I've been stalling on getting a heat pump installed because I figured it would be a good time to get the windows replaced with double glazing at the same time. However, my neighbour who has done this tells me that I can only replace the glass and will not be allowed by the body corp to replace the frames as well.

Am I going to benefit from switching to double glazing at all? Should I just get the heat pump install done because the benefit (or even payback for that matter) from double glazing will be that low? Maybe I just get some of those 3M "double glazing" stick-on sheets on the windows instead? Part of the reason I wanted the double glazing too was to help with noise levels from the outside.

What's everyone's thoughts? :)