House design is an integral aspect of permaculture with passive solar and other low energy input designs. The conundrum is that we really need different designs for winter and summer. In Japan we have cold dry winters and hot muggy summers so the Japanese approach was that it was better to be cool in summer and freeze in winter. If I paint the west facing wall matt black the concrete will absorb heat during the day and radiate half of it back into the house at night. In summer a white wall reflects the heat, which is why houses around the Mediterranean are usually white. Could we develop a paint which changes colour with the seasons? A natural solution is to plant deciduous trees which reflect light in summer but let it through in winter.