As I’ve been running into people who would like to grow more fresh foods in Alaska, the problem of high heating expenses have been common when speaking about getting starts planted a couple weeks earlier in March and extending the growing season a couple weeks out farther into October. In speaking with a biofuels expert at one of the former experimental farms, it sounds as though the expensive space heating people use may not be required. The entire greenhouse, up to the ceiling does not have to be heated for optimal growing results. In fact, just the zone 4 feet about the soil bed is the crucial area- and even more important is the temperature in the soil bed itself. Thus it may be that putting money and effort into heating the soils is where the ‘bang for the buck’ on energy costs lies. This can be done with warming fluids and radiant piping! As long as the plant tops don’t freeze, it’s really the roots that you want to focus energy and warmth on!