This furnace is designed to use in conjunction with your existing HVAC ductwork and works with your existing furnace while leaving the mess outside. With up to 180,000 BTUs, it is designed to heat a home up to 3,000 sq. ft. This unit has an all weather steel shell that is overlapped for a tighter weather seal. Connection to your existing ductwork is easy with the 10” warm air outlet and 12? return duct.