Recipe for disaster. Concrete is porous, and thus absorbs moisture. When wood absorbs moisture, it swells. If it absorbs enough in the lower layer, with the top layer absorbing it slower, then you get cupping. Grooving will not prevent cupping. If you don't fix that constant transmission of moisture to the wood, then you get rotting. Wide plank already moves around a great deal, even when installed above grade on a subfloor. It will expand and contract with the seasons. That's normal. The wider the plank, the more movement you get. You need to maintain constant humidity in order to minimize the normal movement in wood. If you get hot and humid weather in the summer with no AC and don't use a humidifier in the dry winter air, then your wood floors, furniture, and cabinets will swell and shrink considerably over the seasons. That is NOT considered a defect. And this is why engineered flooring was created. It's basically plywood, with thinner layers of cross grained material. That means that each layer has minimal expansion and contraction, and because of the cross layers, it's much more stable. Combine that with a polyurethane glue designed to keep moisture transmission to a minimum, and that's the only consistent tried and true way to successfully have wood floors with slab flooring. It's the only way wood flooring is done here in the South, where humidity and concrete slabs are everywhere. It works, and there is no need to reinvent a square tire and call it a wheel.

Thanks, franztini, for taking time to share your thoughts. I agree with you- Warmboard is great for new construction, it would be quick solution. In your situation, you probably already have some insulation in the slab from your previous radiant heat. My slab has no insulation at all. It is desired that insulation over slab has R=19. This would require 4" thick insulation. I can't raise floor that much and would be ok with R=10 (maybe even lower). Roth panel seems as a great option for slab since it is made of insulation. Also, aluminum on top may heat floor faster. Though, for some reason, I have tough time to find contractors in NJ that have experience with Roth panels. Also, comments related to Roth panels I saw on web seem to be older. I was wondering if there were any issues with RP. The drawbacks - it may be time consuming to install (especially for hardwood flooring) and R value is only 4.5 and no additional insulation can be added underneath. Though, I would still consider if people have good experience with it. Also, there could be some additional tricks to improve insulation such as insulation on perimeter (don't know much about it). I looked at HeatPly. Because it is made of plywood, I would need additional insulation. Also, you may note it doesn't have the benefit of having aluminum on top to heat floor faster. Though it is great that it is provided with boiler and tubing. If you don't need insulation, it may work well for you. I found out that in order to insulate under Warmboard, I would need to use sleepers (rigid insulation will not work). While this will be the right way to provide insulation, this will require raising the floor level. I am taking time to make the right decision but have really hard time with it and the cold weather is around the corner.

Did you ever find out more about Bausen Flooring? It is really interesting. I am looking at the Colonial Collection (http://thecolonialcollection.com/) which apparently is distributed by Artisan Hardwood (http://artisanhardwood.com - not to be confused with Artisan Hardwood Flooring in Texas) and apparently has some relationship to Bausen Flooring (http://www.bausenflooring.com/), The interesting things is that all of them share the identical warranty verbiage with simply a name change. Interesting that the "Colonial Collection" is warrantied by the "Colonial Collection" which as far as I can tell does not exist as a legal entity. That would lead me to believe that the warranty is worthless. All of it seems to be run by Kuo-Tung Liu who is doesn't seem to have much history. The google maps image view of the warehouse in California "18971 Arenth Ave, City of Industry, CA 91748" has a Bausen Flooring sign next to a US Alibaba and another flooring warehouse with Chinese characters that Translates to 'Brothers Flooring Center - Leo Brothers Flooring Center', President Shengyang Cheng. No information on any of the companies on LinkedIn or Facebook. I dont get it?!?

Glad we now agree that 85 is an established threshold that radiant floor designers use as a recommended maximum for floor surface temperature. Foot contact with the floor makes the second way high temperatures lead to discomfort. 85 is evidently too hot for those expecting warm feet and will definitely lead to uncomfortably hot room temperatures, in efficient homes. There still seems to be confusion regarding water temperature and floor surface temperature. The temperature of the floor surface will be lower than the water temperature in the tubing. The water temperature entering the tubing loop from heating appliance, will be warmer than the temperature exiting loop, on its way back to the appliance to be reheated. The only mention I made of water temperature was that 125 seemed too high for an efficient home. Perhaps not for a long tubing run with short spacing but I still think it seems high and engineers generally don't like long tubing runs. I've personally installed tubing on a spec of mine and for other builder friends. We installed short runs with wide spacing for better zoning and they were for efficient envelopes. Few ended up being hooked up to an actual appliance. Why spend that money when the required AC can handle the heating too. The "at" which I corrected to "near" room temperature comments were in regards to floor surface temperature, which is a widely accepted fact for those involved in efficient construction. From All About Radiant Floors: "Why isn’t my floor warm? Homeowners who look forward to walking barefoot over warm floors are often disappointed by homes with in-floor hydronic heating. That’s because these floors are rarely as warm as most homeowners expect." From that article's case study (keep in mind difference of water temperature and floor surface): “On the design heating day [the coldest day of the year], the water flowing through the tubes in the floor will only be at 85 degrees,” said Robb Aldrich, an engineer at Steven Winter Associates" From energy expert Alex Wilson's article describing a level of home performance between passive house and international code minimum: "in a highly insulated house (and I’m talking about a really tight house with at least R-40 walls, an R-50 ceiling, and triple-glazed low-e windows), such a tiny amount of supplemental heat is needed that a radiant floor needs to be kept no more than a few degrees above the air temperature—or else overheating will occur. If a concrete-slab or tile floor surface is maintained at 72 or 75 degrees, it will likely feel cool underfoot—since it’s at a lower temperature than your feet. So you may not get that delightful benefit of a warm floor surface.