COSY

COSY is designed to distribute warm air from the premise in which the source of heat (like [closed] fireplace or wood stove) is situated to the nearby premise. 
The product should be installed in the vicinity of the said source of heat, and the properly programmed thermostat will run the exhaust fan, that will transfer the warm air to the adjacent premise. The fan will turn off when the temperature in the second premise  falls.