Hi Guys, I am having a problem with the heating system in my house. To give you a little background, my house is an end of group townhouse located in Baltimore MD. The house is brick and was constructed in 1952. I have a Weatherking 80pj07ebr01 gas furnace. I am having an issue with keeping heat in my house. For example, I have my furnace set to 68F tonight and the outside temp is 30F. My furnace will run to maintain the heat and shut off. The furnace will kick back on within 10 minutes, so my furnace runs a lot of the time just to maintain heat. It is also much colder in the bedrooms on the upper level. I was patching some holes in the bedroom upstairs and noticed the walls are 1/2 inch plaster and there is only about a 1/2 inch between the plaster and the brick wall, I did not notice any insulation. Also, before I moved in, some return duct work was relocated in the basement. I am not sure if this is an issue with the furnace, the duct work, or the insulation. Are there any tests I can run or readings I can take to help narrow this problem down? It is very cold and uncomfortable, plus I know it is costing a lot to constantly run the furnace. Thanks guys!