Air conditionning = bad
Natural convective cooling = good -- provided you live in the right region and have the proper house
Solar photovoltaics = good, but only if you live in isolated areas with unreliable grid service. In urban and suburban areas, PV are unlikely to ever make sense.
Truly sustainable energy? I hate to admit it, but if we really must supply ourselves with ever increasing energy needs (your house may be better insulated than mine, but the energy involved in building it was probably higher), much less address the needs of the rest of the world, our only short term hope is .... nuclear. I almost feel like apologizing for such a blatant statement, especially since I participated in demonstrations outside Creil Malville in France, back in 197x(?). The fact is that my homeland, France, has now been providing for 85% of its electricity through nuclear power for over 20 years, and that we (thankfully) have not had any bad accident.
Technology has evolved a huge amount in the past 30 years. This is true for reactor design, for control systems, and for waste treatment. France has several re-generators that take the highly-radioactive waste from the cruder/older generators, and extracts further power from it while reducing its radioactivity. I'm no nuclear scientist, but I do have a couple of engineering degrees from the Massachusetts Institute of Technology. As I understand it, the forthcoming ITER reactor, which is scheduled to begin operating in 2020 has pretty high expectations of successfully producing controlled fusion. In the meantime, it is said that progress is forthcoming on methods for further reducing the radioactivity of all current nuclear waste.