Thanks for taking the time to answer. We actually are in the final stages of our basement. Carpet ordered today. We did end up checking with several hvac companies because my builder said he didn't think the unit was large enough to handle the additional space since it was broken into several rooms. Had it been one large space we would have been okay, but we put in a bedroom, bath, media room, gym and playroom all opening off a cental hall. So the basement now has it's own 1 1/2 ton 12 seer heat pump at a cost of $3500. We are in central VA. Just thought I'd post this info for anyone out there who might be in a similar situation. We also paid a drywall guy to mud/tape the drywall. Everything else has been diy. Will post pictures soon.

Leaks in supply ducts depressurize the building. Leaks in returns make the pressure positive. That sucks outdoor air in, and blows it out, respectively, through any air leak in the house. Note this is for "outdoor" ducts only. If you create fur-downs inside the house envelope, you can tolerate duct leakage. Sucking air in randomly causes a lot of problems in my climate where condensation can readily occur. Central ducted AC systems also tend to cause pressure differentials between rooms unless there is a return in each room. Keep in mind that you will have to undercut each door halfway to your knees unless you have a return in each room or install jump ducts of some sort. Ducts in conventional attics pick up a lot of heat in the summer too. These are all reasons that I installed 7, high wall units in my home in the hot, humid South. Keep in mind that there are other types of mini-splits that do involve shorter duct lengths that might be more easily accommodated by fur-downs. There are also ceiling cassettes.. FSQ4CW, do Al and Fe radiators "require" different temps or are they just sub optimal on the same loop? If the latter, how bad is it really?

Talk to a realtor in your area who can give you hard numbers. However, I would have to say that the project is only worth doing if you are able to incorporate that half bath into a master suite and add a shower or tub/shower. Depending on what type of footings were dug for the garage, your project may require demolition of the garage and new footings dug before you can use the space for living quarters. If the realtor gives you an idea of the numbers on this as far as any gain in value to the home, you will then need to contact your local permits office and find out what type of permits and inspections you will need to go through to do this. Do not even think of doing it without, as it creates a big nightmare for you to have unpermitted work at any eventual sale time. Plus, lots of neighbors just live to turn you in to the codes people. Then your third stop is a structural engineer to be able to assess the scope of construction needed for the project. As previously mentioned, the foundation will need assessing, as will the existing walls and roofing structure's ability to be insulated to current code without affecting the required head height. It could be a really simple project, or it might not be. After you have gathered all of the above information, then it's time to develop a written scope of the project with all of the specs for the products that you want to use and the structural requirements of the engineer. Then you use that document to seek bids from contractors so that everyone is bidding on the same project with the same products. For a mid range master, expect costs to come in somewhere between 120-140K if you have to rebuild from the foundation up. If your foundation and existing walls will work, then you can probably shave off one half to one third of that amount. If you DIY everything, then maybe one half to one third off again. So, between 30K and 140K depending on what the reports say and how handy you are.

"A two story home should have 2 separate systems. " This is a townhouse, likely 1500 sq feet +/- from looking at the floorplans. I've never heard of one with two systems. Have you, Austin? Elmer, not all townhouses are 1500 sq feet. So when I say what I say you are taking it out of context for what I mean by it. Meaning you are going to have problems controlling comfortable temps in a 2 story structure with one thermostat. This is regardless as to the size of the structure. Townhomes come in all different sizes. If I don't describe the situation as I have described it the home owner or townhome owner is under the illusion something is wrong with the system when it is really a 'system design' limitation. I don't build townhomes, nor do I build homes. While the structure often limits what I can do to correct foolishness of what architects design this doesn't change the control options of the system does it? At the end of the day, heat still rises and cooling still falls... the thermostat reads in an area of 10 or so square feet around it. If you have a thermostat on upper level it's warmer up there. If you have the thermostat on lower level it's cooler down there. If you want the upper level cooler, the system runs more and the lower level will be colder. This scenario does not change if you move the thermostat, except for the setting in which it's placed at. A structure does not defeat me and what I do, it only limits the options I can present as solutions.