Abstract: This passive solar heating invention is designed to be a single or full window installation (for most sliding and double-hung windows) that is the simplest, lightest, and most cost effective answer to the world-wide demand for clean, cheap, renewable energy. The bias in designing this invention was to give the home resident the option of half a window for viewing. If the resident decides the view is inconsequential, then a full size installation will more than double the heat output of ‘Tersol’ or through wall installation, if feasible. Permanent installation would not increase cost, and would provide for a much larger unit with accompanying output.