No heat in Atlanta. Check and find 21 year old Lennox gas furnace fail due to bad flame sensor. Test and find furnace operating with worn ignition, weak blower capacitor and dirty blower assembly. Duct system dirty and not code due to R6. Find system have not water protection in attic. Find gas line not code at furnace. Due to system age and conditions, suggest to upgrade, customer only want repair at this time. Replace flame sensor and furnace operating. Sign 2 cci plan and need to schedule for summer visit in Spring of 2021 and fall in 2021.