No heat whole home. Found system to be off and turned on. System started running upon arrival. Inspected system findings bug in burner p, dirty flame sensor, cracked heat exchanger, dirty blower wheel, no flood protection and system is in a spray foam attic and lacks proper combustion air which lead to premature failure of heat exchanger. Recommend replacement of furnace. Informed customer of cracks in heat exchanger, advised due to safety concern not to operate the heat. Left thermostat in off position. Advised customer availability of heat exchanger is unknown as manufacturer closed for day. Will update quote and email over in the morning.