[jyl]

I wonder if anyone has experience with split-system A/C systems.

Here is my situation and why I am thinking of one.
- House has basement, main floor, second floor, and finished attic. Total excluding basement is appx 3,100 sq ft.
- The finished attic is where we have the heat problem. It is the family hang-out room, typically have 3-4 people up there, watching TV, playing with Legos, reading, etc. Plus the electronics (LCD TV, etc) which give off a lot of heat.
- Finished attic is appx 800 sq ft. Appears to have been insulated, but only a so-so job - for example, no ridge/soffit vents. Five skylights, fitted with black-out blinds. Various smallish (20" x 20") windows set in dormer/alcoves, but only one opens.
- House has central air but, being an old house that was retrofitted, the ducting is not ideal. Only one small duct (appx 30 sq in) in the attic. There isn't any room to run more or bigger ductwork to the attic, not with the existing interior wall layout anyway.
- Central air does a great job on the main floor, a so-so job on the second floor, and not much effect in the attic. If I close all the main floor vents and some of the second floor vents, it helps a bit in the attic but still doesn't do much. If I point fans up the stairwell from second floor to attic, it helps a bit more. An exhaust fan in the sole opening attic window is also a minor help. But even with all of this, the attic doesn't get enough cooling.
- At outside temps of 90F, the attic is kind of warm even with the A/C running. At outside 95F and higher, the attic is too warm.
- And, in order to get the attic down to "kind of warm", the central A/C has to run a lot. This seems like a waste, since the rest of the house is cool enough. I'm basically running the whole house central A/C just to cool the attic.

Thus, I was thinking of installing an air conditioner in just the attic. I think I need something like 15,000 BTU for that size room.

Window unit? These are relatively affordable, I see 15,000 BTU units cost around $500. But there is no exterior window in the attic that can accommodate a window A/C unit. There is an exterior southern-facing wall where the stairwell comes up, I guess the wall could be cut and a window unit mounted there. Downside: I hate the look of exposed window AC units on the exterior of a house, though. And the A/C condensor side would be sitting in direct sun, on that south wall.

So that is why I was thinking about a split-system unit. The condensor (heat pump) could sit on the shaded northern side of the house, next to the condensor for the central A/C. Downside: Looks like 18,000 BTU single-zone split-system A/C units cost around $1,500, plus installation of course. It would look weird to have two condensors, indeed it seems silly to add another A/C unit when we already have central A/C.

I am going to have the A/C guy look at this situation when he is out here tomorrow. Maybe there is an easier or more sightly solution. But what do folks think? Anyone have a similar problem?