We have a ranch home with hot water baseboard heat with two zones. The living room has a 10 foot bay window and a 6 foot patio door both with thermopane low e-glass and have a southern exposure. The thermostat for the living room zone is located on the interior wall between the living room and the dining room/kitchen on the north side of the house. Both areas are on the same heating zone. On cloudy days the temperature difference between the living room and DR/kitchen are about 1 - 2 degrees, but on sunny days that can vary by 5 - 6 degrees due to solar gain with the living room being much warmer. What can be done to help balance the temperatures between the areas short of installing a separate zone with thermostat, circulator and piping for the DR/kitchen? Could a duct be installed with a thermostatically controlled fan be installed in the partition wall between the DR/Kit and living room to help balance the temperatures?
Re-piping to create a separate zone would require the addition of a separate circulator, changing out the three zone control (one zone for domestic hot water) with a 4 zone control, about 100' of copper piping back to furnace at opposite end of basement, and addition of a thermostat. All are doable, but is this the least cost solution? Would the use of two zone valves to split the one zone be a possible solution? This might mean use of less piping, no changing of controls, and no new circulator. Any suggestions/experience on use of a through the wall duct fan?