If you're renting in Christchurch and dealing with a cold damp house, here's something that actually made a difference for us: getting a dehumidifier. I know they're not cheap but we picked up a secondhand one on Trade Me for $50 and it pulls litres of water out of the air every day. No more mould on the windows and the heat pump actually works now. Also check if you qualify for the Warmer Kiwi Homes programme – they subsidise insulation and heating. Lifesaver.