The built environment is responsible for 37% of global emissions; most of this from heating and cooling. We must transform the way existing buildings consume energy and make them more efficient (it is insufficient to only build new buildings according to "sustainable guidelines"). Better insulation to reduce heat leakage is a key step. According to the International Renewable Energy Agency, 20% of buildings need to have a deep retrofit before 2030 for us to have a chance of meeting Paris targets... While no country is on track, some set good examples. Some areas of France have trialled a low-cost retrofit model including thermal insulation, triple glazing etc. In Australia, 30% of homes have a solar voltaic system, and the UK shift from gas boilers will have significant impact. But, quick enough? Governments should examine the progress of other countries, benchmark their progress and get going forward. "If it works for them, could it work for us?" We don't need a million new ideas, but a few good ones shared.