A recent, somewhat experimental solar heating system "Annualized geo solar heating" is practical even in regions that get little or no sunlight in winter. It uses the ground beneath a building for thermal mass. Precipitation can carry away the heat, so the ground is shielded with skirts of plastic insulation. The thermal mass of this system is sufficiently inexpensive and large that it can store enough summer heat to warm a building for the whole winter, and enough winter cold to cool the building in summer.