Bioclimatic approaches harness natural processes to heat and cool buildings, through appropriate choice of materials, location and design. This allows maintenance of desired internal temperatures over a wide range of external conditions, future-proofing buildings against changes in weather patterns and possible temperature extremes. When built using natural materials, such buildings can easily be low-carbon or even carbon-negative in their operation: heating and cooling needs are low and can employ renewable sources, and many use natural building materials that are also carbon sinks.
Straw bale houses are a feature of permaculture projects in temperate and Mediterranean climates from Ireland and Northern England1 to Italy.2 Sieben Linden Ecovillage in Saxony houses most of its 150 or so residents in a series of multi-occupancy straw bale buildings.3 Main facades and most windows face south to capture winter sun and are carefully shaded, minimising unwanted heat gains in summer and losses in winter. Supplementary heating comes from solar-thermal collectors and wood-fired stoves, most highly efficient in design. Research conducted by Kassel University showed that per capita GHG emissions associated with Sieben Linden's housing and heating are, respectively, ten percent and six percent of the German national average.4 Wood for both heating and construction is cut from Sieben Linden's own forest as part of a long-term habitat enrichment programme, replacing extensive conifer plantations with more climate-resilient high-diversity native broadleaf woodlands.
The Central Rocky Mountains Permaculture Institute has developed innovative low-energy systems to regulate temperatures in the five large greenhouses onsite. These 'Climate Batteries' use fans to pump warm, moist daytime air underground where the water condenses, capturing both the thermal energy and the latent heat of condensation in the soil. This provides warm, moist soil conditions ideal for plant roots even at far lower above-ground temperatures It also allows stored heat to return from the soil to the greenhouse interior in cooler weather.5 The greenhouses form part of a wider bioclimatic design incorporating systems for heat exchange with adjacent buildings and thermal masses, allowing greenhouses to be heated with residual heat from the sauna and living areas.
An integrated greenhouse and residential dwelling is also crucial to the bioclimatic design at Melliodora in Hepburn Springs, Australia.6 The greenhouse acts as a temperature regulator for the house: providing an 'airlock' for one of the two main entrances, warming living spaces in winter and cooling them in summer. The house also incorporates substantial thermal mass: north-facing internal masonry structures that absorb the heat of the Southern Hemisphere winter sun and release it to the rest of the house. Partial shading by annual plants in the greenhouse and eaves over all north-facing structures reduce their summer exposure to the sun and so help keep the house cool.