We recently bought a remodeled attached townhome (3 story with a basement). It’s a 1 zone system with return air grills at each floor (center of the house), and ceiling registers for forced air (cool/heat) on the 2nd and 3rd floors. The handler is on the 3rd floor, and the condenser is on the roof.
We use the basement as a media room, with TVs, computers, etc. The basement has a return air vent, but no registers to force cool air down. It can get quite hot in the basement (+ 6-10 degrees more than the upstairs). We partially blocked some of the air intake in the other 2 return air grills, which made a partial improvement (more cool air circulates down as more air is pulled through the return air in the basement). Of course this risks freezing the compressor, so we're cautious about this as a long-term option.
I’ve had all 3 options proposed by different contractors and am curious what people’s thoughts/experiences -
Enlarging the return air grill in basement and blocking off some of the return air in the other 2 vents using closeable louvers or something similar (more circulation in the basement and more air pulled out of basement, bringing down cooler air from upstairs)
Installing a split ductless system in basement as a separate cooling system (more expensive than option 1; requires some significant installation of cooling pipes, electrical, etc.)
Running 1-2 ducts from upstairs to basement as forced air ceiling registers in basement (also expensive; requires labor hours to install and repatch drywall)
Thanks in advance!