High velocity is really for retrofit - it is more expensive and not as good. High ceilings are great and so are fans but a/c is a lot about humidity anyway.

I hope you and your building professionals are planning on putting your ducts inside the house envelope.

Ionized - while that is ideal, if they were in a crawl space or unfinished basement and only used for a/c, that really isn't a big deal.

If the crawl space is sealed and within the envelope of the building, I would agree. If not, the the ducts are outside and that is generally something to avoid.

Hi David Cary. Ionized is right. I have two beach houses, both with unsealed crawl spaces and the a/c ducts are in them. If the crawl space smells bad, the a/c smells bad. I have smart vents in one of the houses so was able to install a high efficiency dehumidifier which has done the job of keeping the moisture low enough to reduce the odor. Also, be careful what kind of insulation is used in the crawl space (between floor joists). In one of our homes, Dow Pink Panther was used and it smells like cat urine when it gets damp!

We have high velocity in our city home (retrofit 120 yr old house). We are very happy with it but I wouldn't install it in a new build, It's expensive, loud and not as efficient as a standard system. You can really hear the air rushing out of those small ducts.