We moved in to our home in July and are beginning to run the heat. We noticed in the summer that it was much cooler upstairs than downstairs (very unusual, we thought)and the complete opposite in cold weather. When the heater is on downstairs, we can feel very warm air blowing from the vents and it holds the temp. we set it on... however upstairs, it feels cool when blowing, though it is actually a few degrees warmer than the room. Why the difference? The upstairs also runs continually in the evening when the temps outside are in the 40's & 50's, barely keeping the temperature up where the downstairs will come on and go off as it regulates the temp. The upstairs is obviously having trouble somewhere. We've changed the filters and the attic is insulated. Somewhere online I read something about copper pipes outside needing to be hot so I went out to the unit while the upstairs was running to see what they felt like. There are two and they were both cold. Thank you for any suggestions!