I live in a two story condo in Denver, built 1972. Stupid furnace is in a closet upstairs, thus during extreme cold weather the downstairs can be as cold as 55 degrees and we must use electric portable heaters. We replaced the HVAC 15 years ago. Feel like I got sold an inadequate system. Starving for intake air according to one service tech who serviced it in recent years. Ducts other than those in the closet are all behind drywall. Hot air duct to downstairs goes off the back side of the furnace, hot air for upstairs comes off the front of the furnace and includes a baffle to supposedly help regulate the amount of air allowed up/down. No clue how to effectively set the baffle. Looking for the terminology related to getting gas furnace which has two stages / thermostats to provide better heat downstairs. Cooling is less of a problem. Have new windows and decent but not great insulation.