I'm amazed at the depth of information and insight here. I'm hoping y'all can give me some advice.

My wife and I are buying our first house, in Washington DC. It's a 1918 American Foursquare (Craftsman, Arts & Crafts). About 850 square feet on each of the first and second floors, maybe 400 square feet on the third floor, and then a 800 square foot basement. The basement flooded in the past, but out inspector assures us that regrading so the land slopes away from the house, a swale, and reworking the gutters will take care of that.

We're installing hvac for the first time. Our general contractor recommends a high-velocity AC system (along with the existing radiator heat), which makes sense to us. He's saying that either we could do a dual zone, with the basement and first floor on one zone, and the 2d and 3rd floors on the other, or a single zone for he 1st, 2d and 3rd floors.

If you have any thoughts on high-velocity AC generally, or the one zone versus two zone, I'd appreciate hearing them, but that's not the main reason I'm writing.

Because we're concerned about moisture in the basement, our contractor was making noises about installing a heat recovery ventilation system. Looking at that, it basically looks like a heat exchanger to me, which seems more likely to add maintenance hassles than to significantly reduce energy costs (especially after cost of installationg). What do you think? Any thoughts on HRV generally?

More importantly, after looking at what I've seen on hvac-talk, what makes sense to me is to install an whole-house dehumidifier, acting on both fresh air intake, and on the return air, so that we can keep RH below 50%. Also, that way, we can run the dehumidifier when the weather's right and not run the AC, which should save on energy costs. Any thoughts on a whole-house dehumidifier versus an HRV, or a whole-house dehumidifier in addition to an HRV?

Also, do you know which whole house humidifiers use a standard filter, as opposed to a custom one?

Finally, can you recommend any good AC contractors in the Washington, DC area? I don't know who our general contract works with, and I'd like to have some options.

Thank you, very much.