This passive solar addition transformed this nondescript ranch house into an energy efficient, sunlit, passive solar home. The addition to the rear of the building was constructed of compressed earth blocks. These massive blocks were made on the site with the earth from the excavation. With the addition of foam insulation on the exterior, the wall becomes a thermal battery, allowing winter sun to heat the blocks during the day and release that heat at night. The house was built with only non toxic or natural materials. Heat and hot water are provided by a 94% efficient gas boiler which warms the radiant floor. A new wood fireplace is an 80% efficient, low emission unit. With Energy Star appliances and LED lighting, the energy consumption of this home is very low. The addition of infrastructure for future photovoltaic panels and solar hot water will allow energy consumption to approach zero.