Hello
What kind of healthy choice moisture retarder would you recommend for hardwood floor for the 2nd floor ? I have looked through many options such as felt, hwd-15, aqua bar b, kraft, and they all seem to be coated with asphalt.

I used Aquabar 'B'. The asphalt is sandwiched between layers of kraft paper. The company literature says there may be an asphalt odor but I have never detected any and my wife who has a very sensitive nose has never detected any either. It's also a nice clean surface to work on and the wood slides easily across it. I don't work for the company....in case you were wondering.

2nd the aquabar