It's a good point, but PEX is installed above the sub-floor to circulate the heat and then the mud floor for the tile is installed on top of it. It shouldn't add any height, since the mud floor already has to be 1" to 1-1/2" thick.

we live in MN and it was 68F around dinner time. the indoor temp was 78F according to the remote control thermostat i saw on the counter. pretty cool unit. almost like a fancy remote for his home theater. i could feel the air coming from the high velocity ceiling vents and wondered what was up? why so warm? a cloudy windy day yet the house was very warm.

Thank you all for the advice. Here's how the problem was resolved... (Sorry for my lack of knowledge and correct jargon) For the second floor heat (in our 45yr old+ house), apparently there is one loop of piping and each radiator has a supply and return coming off this loop. The hvac person installed valves (in the basement)on the supply and return "T's" of the problem radiator and also replaced the circulator pump with a variable speed circulator (so that he could push more water through). With the valves, he was able to shut off the flow to each end of the radiator (1 at a time)and was finally able to get the air out. He said the supply line is connected to the end of the radiator DISTAL from the bleeder valve - but that it doesn't matter...since it is a complete loop. This doesn't really make sense to me... but the heat is working now. By the way he said that he connected the radiator as it was before, and it must have been like this all along...??? So, hopefully my problem is solved, and we will not have constant problems with this radiator...???

We actually replaced the York A/C units with Trane A/C units and coils. The new coils fit right into the existing supply ducts. We left the York gas heat units alone - and everything worked great. I had two HVAC systems - one in the basement that serviced basement and main level and one in the attic that serviced second floor. On the inside, each system had a gas heater unit and a seperate A/C coil that was mounted just above the blower fan (the blower was integrated into the heater unit) and the output of the coil unit connected to the supply air duct. If you have a system like that - I can't see why you would have to change out the heater unit if only the A/C needed replacement. The one issue we faced - and another reason I upgraded - was that the original A/C system used a type of refrigerant that was outlawed (maybe it was freon - I cannot remember.) By the time we got to 2003, the replacement refrigerant they were using was also outlawed by a certain date - lets say 2006 (memory going). You could still get the this replacement refrigerant through 2010 BUT the equipment manufacturers were starting to make units that conformed to the new standards. I was told the potential issue was that my copper lines running from the outside units up through walls to the 2 inside coils were not the corrrect diameter for the new mandated refrigerant. So if I waited too much longer the cost to replace the outside units, which would soon conform to the revised environmental standards, would have been much more since the copper lines would have had to be replaced as well (which would have meant tearing out a lot of drywall and repairing the mess that goes with it.). That was the only integration issue we faced - all avoided by using new equipment, but equipment that was not designed to the future standards at the time. I would get some second opinions on A/C replacement when it comes time to do that.