I just found this site! Hopefully someone can guide me. I just bought a small old house - 1 story. It has a Wesco electric furnace, mfg date 12/27/1980. There are cold air return ducts in every room except bath, located at the bottom of the walls near the floor. The heat vents are located in the ceilings of each room. I want to raise the ceilings in kitchen, 2 bdrms, and LR/DR as the ceilings are very low. Can I change existing ducts to have hot air travel through the existing cold air duct system, and use a couple of existing hot air ducts to supply the cold air return? In essence, I want to reverse the function of existing ducts: hot would become cold, cold would be hot (with new insulation). Is this possible? Thanks!
JJ

Anything is possible but the expence will be great. The duct size is probably be wrong when you change the function for the ducts.

Anything is possible but the expence will be great. The duct size is probably be wrong when you change the function for the ducts.

Since I'm going to raise the ceilings I will have to reroute the existing hot air ducts to someplace other than the ceilings. Do you think rerouting the existing air ducts will be cheaper than than reversing the function of the existing ducts (and whatever it takes to do that)? Why are the ducts different sizes? Thanks

Reroute will be cheaper. Return and supply diuct are engineered differently for air flow and capacity. You might check with a local HVAC company to get a bid and ask them what would be best for you under your circumstances. It does not mean you have to buy from them but the job could be over your head as far as engineering/sizing/flow rate/ etc. Your furnace is also getting old. You might consider a heat pump to decrease your utility bills.

Do I need to find a local HVAC company that carries my brand of furnace to give me a quote? Or can I go to any HVAC company? If I decide to get a new furnace/heat pump, can my existing ductwork be used or do I have to pay to rip it all out and start over? This sounds ridiculous, but can I run the furnace upside down and have it blow hot air down through the existing (insulated) cold air ducts and use the existing hot air ducts in the ceiling as my cold air returns? OR if the cold air return ducts need to be larger than the hot ducts, I could just upsize the ceiling ducts. I am an engineer, so is there a formula I can use to figure out all sizing/flowrate, etc? I just don't know the science behind forced air furnace efficiency. You have been very helpful - thanks!

((can I go to any HVAC company))
Yes you can and I suggest you pose your questions to them since they will be the ones seeing your system and what can be done with it.

I will call a local HVAC company and ask their thoughts. Thanks for you're your insights. I appreciate the guidance.