I've purchased a masonry Cape Cod built in '47, and in the interests of efficiency, I'm looking at making a few changes, but I have a few questions...
First, the registers are all run through internal walls, and are placed about 10" below the ceiling. The cold air returns are all on outside walls. There ground level is almost always noticeably cooler, enough cooler to never want to leave your feet dangling off the couch. This is true in in all rooms. Would there be any advantage in bringing the registers down to floor level? In most rooms, this wouldn't be too difficult.
Second, I have two unused bedrooms upstairs. I have closed the registers in those spaces and installed a heavy decorative curtain at the lower entrance of the stairway to reduce air movement. Should I close off the cold air returns as well, or will that create problems?