I am having it put into my house right now, so I will ask my contractor what type of wood he is using on the kitchen floor. It does have to be some special wood, but I am sure my meticulous contractor will match it to the rest of my 100 year old wood floors.

I will ask him about it tomorrow and report back.

Semi:

we just did it in our house (new construction) and they had to use quartersawn oak instead of regular oak.

Five years ago I moved my kitchen into a new 2 story (1 room per story) addition with hydronic radiant heat. Both floors are 3.25" red oak, regular cut. It is installed on 3/4" ply with the radiant plates (Thermofin) installed into the underside of the ply. The heat works fine. The oak boards have some narrow spaces in the winter which close in the summer. Nothing dramatic. No cracking, splitting or drying out. The wood floor does not get hotter than it would on a hot sunny day with no a/c. I installed very little pex under the fridge which generates enough heat of its own.

We have radient heat in our kitchen/family room. The advice I was given was to use engineered hardwood rather than "regular", to minimize the wood expansion/contraction. I liked this idea for the kitchen especially, where food etc may be dropped and don't want cracks for it to fall into. My flooring place actually wouldn't warranty hardwood over radiant heat, even though an installer said you could do it if you knew what you were doing. The floor does have to be floating.

Hth!

Thanks for all of the replies. I'll give some more background info. The first layer is the existing subfloor which is real wood, it looks like a 2x4, but the size is actually about 3/4" x 3.5". The subfloor has 1/4" or so gaps between each board. The second layer on top of the subfloor is the existing wood floor, which is real wood. It looks like oak and must be regular cut, but not entirely sure. It has alternating widths of about 3/4" x 3" and 3/4" x 5". It currently has some gaps between most boards about 1/8" or so wide. We plan to install real wood flooring on top of that, but not sure what species yet. Are there certain species that won't work? It sounds like I may have to get a certain type of cut. Do you think it will be okay to install the new wood floor over the existing wood floor, or is the old wood floor likely to buckle underneath if it expands too much?

All solid wood floors move a little, seasonally, unless your home is tight as a drum with consistent temp and humidity year 'round. Radiant heat exacerbates this problem, ESPECIALLY in a solid floor, and the wider the boards are, the more pronounced it will look. I don't know how much heat will radiate through three layers of flooring, but your current subfloor[s] are acclimated to your house but not to the added heat. If those two lower layers start to shrink from the new heat they could bring your new flooring with them. Engineered flooring moves less, narrow boards move less, quartersawn moves less. You should talk to a professional flooring installer who is familiar with both your flooring choice and radiant heat systems before proceeding.

Another with radiant heat under wood (pine planks) - In a couple of rooms we went right over the oak with the pine and still get plenty of heat.

We put in hydronic floor heat in our basement where we poured a layer of concrete over the existing concrete. It works well and it is nice to have a warm floor in the winter. Our carpeted basement was actually not that cold before..... I am not sure if I would do it again. The cost differential is pretty substantial.

Get a detailed bid from a reputable HVAC people regarding hydronic floor heating versus baseboard radiant heating. You may be quite shocked at the differential cost.

If you keep the old floor and install another floor over that, what happends to all your doors? They will have to be cut down. If you have hollow core doors, you may not be able to cut down that much. You may have to get all new doors. Did you account for that cost?