My son currently works as a 3rd party engineer for one of the felt rug padding and carpet padding manufacturers Rug Pad USA, Mohawk, Shaw.... and I've actually asked him this same exact issue. I'm a designer down in Savannah GA and our summers are as humid and muggy as they come. I asked him specifically what pads would work to avoid the "Sweating" issue. My clients and I complain about this all the time - the pads get glued to the floor. One of my clients had to replace a portion of their hardwood to fix this issue. He has an engineer background does this for a living, thus most of what he said went over my head....but here's what I gathered... - A 100% felt rug pad is actually recycled polypropylene fibers but it won't ever stain, nor sweat, but the rug has to be large enough not to move. But with smaller rugs, you need to stick with a rubber or latex product to prevent "sweating" and sticking. - Felt and rubber rug pads are made with either synthetic latex (lower cost) or Natural rubber (more expensive), he thought that both should be dry enough that they shouldn't sweat between your floors. So this is what I have been recommending to my clients. I also asked him about the different materials - since I told him one of my clients floors needed to be replaced. Heres what he said "your flooring surface finishes are whats important, not whats underneath them, and to be especially careful with vinyl, acrylic, and laquered finishes. Some PVC padding, not all, can leave an imprint on this type of flooring if they don't get the formula correct, or if they use cheap fillers rather in place of proper materials, or if they haven't been tested on before. Pads that tend stick to floors, melt, sweat, are always made with pvc and essentially all come from low grade suppliers in China." Some food for thought :) - Hope this helps

SJ McCarthy - Thanks for the info. I was also thinking the same thing. The hardwood floor manufacturer is Shaw. Funny, I spoke to a person yesterday at Shaw who told me no rubber-even natural rubber- because it doesn't breath and to use a vinyl backed rug. I called again today and was told by another person to use a PVC pad. I'm confused as it's my understanding that a natural rubber pad that is needle punched, like rugpadusa carries, allows the floor to breathe whereas PVC/vinyl could react to the floor finish. Not sure what to get because vinyl/pvc pad makes me nervous about staining/ruining he floor finish. Any suggestions?

PolyETHYLENE (PE) is safe with hardwoods. It is a completely different chemical than PVC (vinyl), latex (natural rubber) or rubber (man-made rubber).

Natural backings (jute, cotton or even polyweaves). You can find rug pads made out of a 'felted' material like rugpadusa.com These guys know there stuff. You are looking for the tag, "Safe for Hardwood Floors". Here's a hint: Mid-grade or higher decor stores will have them (Ikea has many options) whereas places like Walmart or Target do NOT.