I'm hoping some of you can offer some advice on how best to add a second AC in our home -- or on whether we should look for a different solution. I should say upfront that I've done a lot of reading on this topic and feel more confused than ever. I'm not crazy about the idea of an attic AC (leaks, cost, efficiency). But I also want my pregnant wife and soon-to-be newborn to be comfortable. Some of the more popular alternatives won't work for us, whether they're minisplits (wife hates the look) or a whole house fan (wife has bad allergies and we try not to open our windows because of friction / encapsulated lead paint).
Anyway! We live in central Indiana in a 1920s brick colonial -- no insulation in the walls, a few inches of cellulose in the unfinished attic. The house is about 1700 square feet and currently has a newish Lennox 2.5 ton AC, but while the house has plenty of supplies and returns downstairs there are no returns upstairs. (There is a supply in each room upstairs -- I'll put a copy of the upstairs floor plan, about 750 square feet, at the end of this post.)
In the summer there's a noticeable difference in temperature and mugginess between the two levels, and I really hate the idea of making the downstairs freezing during the night just so the upstairs is bearable. We're considering putting a second AC in in our unfinished attic with the idea that it'd allow us more comfort and more control.
We've received three bids -- the two I'm still considering are in the $4800 range for the labor, second condenser, air handler, and a low-powered electric heater if we ever need to supplement in the winter.
A couple questions in case we go with the second AC. Based on the floor plan below, would you put a supply and a return in each room (one bid's proposal) or just put a supply in each bedroom and a bigger return in the hallway, near the stairs (another bid's proposal)? I imagine we'll be shutting the doors more with kids, but there's a big gap between each door and the floor since the previous owners had thick carpet and tile, which we removed.
Second question: how much do we need to worry about the ductwork and unit being in the very warm attic, outside the house's "envelope"? I've asked both vendors about this, based on my reading online, and they both said it wouldn't be an issue with our smaller house -- and that the AC units will have insulated cabs and that the ductwork will be insulated, too.
Of course, this second AC may be a terrible idea in the first place given the possibility of water leaks and inefficiency and whatever else. So third question: would finding an unobtrusive way to run one return up the second floor hallway and sealing / insulating the heck out the attic be worth trying first? (I don't want to insulate the walls because that's very tricky with brick.) Maybe one return plus a better attic solution and possibly a portable AC unit will be enough.
Or maybe there's a way to do a permanent attic AC smartly (and to make my pregnant wife happy). Curious to hear your thoughts. Sorry for the novel length post! If I've forgotten to add any details please let me know.