Alright....in the middle of the change out. Air handler (Trane Tam7) and condenser (xl15i - 4 ton) is installed and now they are working on the duct work. Turns out main duct was internally insulated with a 1" fiberglass duct liner. Their plan is to keep this because it was done well and in good shape and then use 3" fiberglass duct wrap. Installer said it should give around an R11. Any reason to question whether or not internal insulation should be removed?

Those are valid reasons and at that cost I would probably go with it, but that is completely up to you. Another way you could look at is: get the Performance 13, and when the furnaces fail replace them with variable speed furnaces that will increase the SEER by about the same amount that you would by going with the Performance 16 models now. There would likely not be a combination rating to quantify any such efficiency you would gain with the new furnaces, however. If you get the Performance 16 now you will have a documented, AHRI matched system with a specific SEER and EER. I am more concerned with what he said about his selection of ADP evaporator coils (which you have been quoted), not ones manufactured by Carrier and designed to be used with their equipment. In a straight cooling application, the ADP coils are not a problem with an indoor TEV (metering device), but I personally much prefer to match manufacturer-manufacturer with split systems. Carrier aluminum evaporator coil model number would look like CNPVP****ALA. This post was edited by ryanhughes on Sat, Aug 31, 13 at 11:18

When we bought our house, it had a built in wall unit. That is basically a huge window unit that went into a hole cut in the wall instead of a window. For winter (in South Dakota) the thing was wrapped in insulation and then heavy plastic, and then a wooden box was put over all that and attached to the house so it would stay. On the inside, we got good quality window plastic wrap, and taped along the frame and effectivley shrinkwrapped the opening into the house. Then since the frame was bad and cold air was coming in between the frame and the wall, we ended up putting another layer and extending right out onto the wall. That helps a lot - when you have windchills around -40, you really want to stop that cold air! When we remodeled we went to window units. So much easier to take the unit out of the window and simply close it!

When I was young, the only a/c that we experienced was at the movie theater. I believe that is why my father insisted on the drive-in instead. As I have aged, I find that I am less tolerant of the heat. The thermostat is set at 76 during the day and sometimes that seems warm to me. I can fix that by removing some of my clothes (shades are down, thank you). At night, I need to wrap myself in the blanket, almost mummy-like. Ceiling fan is operating and the programmable thermostat kicks in about 11:00 (when the price of electricity is much less) and it cools the house to 68. Rarely during the day with the a/c come on. The house (walls, carpet, ceiling) have chilled during the night and all will be OK. We cook mid-day and evening meals on the grill, thus not much heat is created in the kitchen. The other day, I did a bunch of canning and that heated the kitchen (good bye clothes), but the other end of the house was still cool. Jim