I searched a bit and found various threads about aquabar and it seems like a no brainer for this particular install. This is in northern VA. Wood is hand scraped Anderson maple.

I'm putting down hardwoods on 70% of the 2nd floor including the master bedroom. This bedroom happens to be above the garage entirely. The garage is neither heated nor cooled. There is insulation between the garage and the bedroom. The heating ducts also run through the same space. Garage floor is epoxy coated. Garage walls are finished/painted but no insulation. No identifiable moisture issues in the garage currently but it's a 3 car so doors opening/closing all the time basically means it's like being outside with a slight temperature buffer.

Anyway, I was thinking of using aquabar for the bedroom and regular rosin for the rest of the level that isn't above an unconditioned space. The wood will be acclimating for 2-3 weeks. Haven't done a moisture test yet.

I had read that some people have a sensitivity to felt paper and that's the last thing I want. It would suck to put a floor down and start getting sick because of the paper. So, I plan on buying a roll of aquabar and just laying it out for a week to see if I can smell it.

Starting to ramble now but just trying to see if I'm missing anything. Acclimate, check moisture, check aquabar and go for it. Have any of you heard of any smell/sensitivity issues with aquabar and whether or not I can do half the floor with it and the other half with rosin?

I used Aquabar in my entire house and never detected an odor. The Aquabar literature says there may be a smell. If there was a smell my wife would have picked up on it for sure. I've had it uncovered on subfloors for days and there was never a smell. Aquabar's asphalt is between outer layers of heavy kraft paper. I would use it everywhere instead of rosin.
I don't work for Aquabar. HD has it for approx. $22 per 500 sq ft roll.