If this is the wrong category, please move to the correct one.

For 1.5 years, I have struggled with what I think is the most a$$inine design of a heating/cooling system ever devised. Not only has it been the cause of much financial misery, but also vexing frustration. And since I am wits end, I am about to institute some sort of jury-rigged contraption to stem the tide.

We live in the foothills of South Carolina (winter lows in the teens and summer highs near 100, USDA Hardiness Zone 8a-7b) and we rent a 2 story 2100 sq ft 4 br 3 ba on-slab house with the 2 air handlers in the attic, two 14×20 intakes (one upstairs and one down), two units on the outside of the house and two thermostats inside (downstairs centrally located and upstairs centrally located right at the stair landing).

The root cause of the problem that allows the transfer of heat in the winter and cool air in the summer is the open floor plan around the stairway which probably measures 10 ft wide by 20 ft long measured at top of stairs, thus allowing unrestricted airflow between the two floors. As if that was not bad enough, two of the registers are too close to the unrestricted up-down airflow corridor. One is in the ceiling 3 feet away (with no archway between it and the up-down corridor.) The other…and this is where it becomes a$$inine… is on the vertical wall of the up-down corridor about 2 feet above the lower ceiling height.

In the summer, things reverse and we struggle with the upper unit running non-stop as lower level heat rises and upper cooling sinks. The sinking cold air never lets the lower thermostat turn on. I have to put a sweatshirt on in the morning to go downstairs and get breakfast while upstairs is mildly uncomfortably warm.

In the winter (as in last night (21 deg F)), we struggle with the lower unit running non-stop, with cold upper level air sinking and newly generated heat on the first floor zipping right upstairs through the corridor preventing the upper thermostat from ever turning on. Unfortunately, the door archways of the upper bedrooms and bathrooms prevent some of this downstairs generated heat from warming the bedrooms. With the upstairs thermostat not stimulated to turn on ALL night, the bedrooms become quite cold.

In the end, we have increased utility bills, frustration with imbalanced temperatures, and either unit getting run no stop for 3 months at a time in their due season.

A few weeks ago, I had closed off the 2 offending registers (which were basically only broadcasting newly generated heat right into the up-down corridor of air). That helped a little, even though they still leak a good bit of airflow. But the real problem is still with 4 other registers pumping hot air at first floor ceiling level and basically a 200 sqft hole leading upstairs and so the problem still persists.

And now, I feel it is time for desperate measures and my wife is not happy about my proposed plan. My plan is at the top of the stairwell landing (which is easier to do than the bottom) is to install a curtain track in the ceiling and have a retractable curtain that can be slid around the upper stairwell landing, similar to those curtains in emergency rooms to separate patients. With a thick enough curtain, I think a good amount of airflow could be prevented, with some loss around the bottom and especially the top near the curtain rings.

Before I go down this path, any other thoughts? FYI, moving is not an option this time. I want to say in advance that I appreciate the help of those with the knowledge to help me fix this.