We did some research on this for our own home. We found out that there are a some issues to think about with wood floors and radiant heating.

The first is the fact that a solid hardwood floor needs to be nailed down. The only product we found on the market that can be nailed through is something called Z- Mesh. Not sure if there are issues with electric fields with Z Mesh. Some electric systems apparently emit low-level radiation that may or may not be harmful. NOTE that this is something that we read briefly and we are not speaking from any perspective of authority on the matter.

Other flooring systems can be installed under a glued-down engineered hardwood floor, but the glue joints have been known to separate. Because the wood is in direct contact with a heat source, it expands and contracts more than it would otherwise.

Installing a hydronic system under a wooden floor just doesn't seem prudent to me. A friend of ours recently had a flood in a semi-rural log house when their hydronics burst. The home has acquired some interesting curves. The hoses leaked water on to the first floor and into the basement.

We are still thinking about the Z-Mesh, but we're going to have to find out some more about the electro-magnetic field issue.

We just put hardwood over hydronic radiant heat. The heat is provided by warm water that runs through plastic tubing attached to the previous concrete foundation with gyp-crete poured over it. We went with 6" white oak engineered boards which were glued down. We chose rift and quarter cut for the oak which we were told would be much more dimensionally stable. We let the gyp-crete floor dry for two months, then let the wood sit in our home for three weeks, then had it glued and let it sit for three more weeks, then will finish it next week. I was told that you must use engineered flooring over hydronic. There are other ways of doing hydronic radiant heat without the concrete. You can also use an electric mat, which I didn't investigate. You must consider that this will raise your floor height, in our case about 2 1/2". It wasn't a big deal for us, since we did the entire ground floor of the house. We had previously had heating ducts incorporated into our slab foundation, and we had ground water leaking into our system.

We have solid wood upstairs (forced air heating upstairs) and you can't see the difference. That being said, we used tile for the kitchen and family rooms (LOVE the warmth underfoot). The hardwood is just in the dining room and living room.

There's one other that I know of that can be used with hardwood, as well as tile and other floorings. Do a search for a system called Warmly Yours.

If your heat is hydronic there's a wonderful but pricey product called Warmboard that is good for nailed down wood floors over radiant heat. Basically, its a plywood subfloor with grooves cut into it for the pex tubing to run through. It's also lined with aluminum to keep from losing heat out the bottom. Heres' some info I received from my architect on the subject (she is a great advocate for green building and has cherry thoughout her house installed over heated floors).

"Not all species of wood are good candidates for an installation over radiant heating. It's best to follow the manufacturer's recommendation for a species' suitability over radiant heat. When possible, choose a species that is known for its stability. Wood species of oak, cherry and ash are slightly more stable than maple and hickory. American cherry, American walnut, Douglas fir, red oak and antique heart pine work well with radiant floor heating. Quartersawn or rift-sawn flooring is preferable to plainsawn in the search for stability. Strip flooring is also a better choice than plank flooring, because narrow boards expand and contract less than wide boards do. Using narrow boards also means there are more seams in a floor to take up movement. Because of its dimensional stability, laminated flooring is another good choice.

. According to the Wood Floor Covering Association (View their radiant heating articles at http://www.nwfa.org/member/magArticlesDisplay.aspx?id=2&catId=22) Darker woods will show gaps and cracks less than lighter woods.

In tests, quarter sawn wood produced 45% less swelling than plain sawn wood. Click here for more information about the differences between plain sawn and quarter sawn hardwood. Particular attention should be given to the r-value of the new wood floor to maximize heat transfer and minimize utility costs. The lower the r-value, the better. For more information about r-values for wood floors, we recommend that you visit this page on the Launstein website: http://www.launstein.com/radiant-heat/r-values-swelling.htm.

The swelling percentage is the percent of wood swelling from the oven dry to green or again the shrinkage from green to oven dry. The higher this number, the less dimensionally stable. Radial cut or quartersawn wood exhibit a low percentage compared to plainsawn or tangential cut. Naturally, the lower R value wood is the preferred floor over radiant heat.
Quartersawn in wider planks is the wise choice.

Species
R values
3/4 inch Thick
R values
3/8 inch Thick
Swelling %
Quartersawn
Swelling %
Plainsawn





Ash (very good)
0.90
0.45
4.8
7.8
Beech (not good)
0.72
0.36
5.5
11.9
Cherry (very good)
0.90
0.45
3.7
7.1
Hickory (good)
0.66
0.33
4.9
8.9
Maple (fair)
0.90
0.45
4.8
9.9
Red Oak (very good)
0.78
0.39
4.2
8.9

Tests have shown that if you do not follow these recommendations and install, for instance, a thick 3/4" Maple wood floor with 4" planks, plainsawn, you may observe issues even when keeping the floor at 80 "

Here is a link that might be useful: Warmboard

We used engineered hardwood, Silver Oak by D&M flooring (not sure how that floor would fare in a kitchen, would need a heartier finish). The installers glued it down. No problems in 5 years.

This is a good article: https://www.builddirect.com/learning-center/flooring/can-you-install-engineered-hardwood-over-underfloor-heating/

Bottom line: Look for waterproof engineered hardwood and glue it down. Follow the manufacturer’s installation recommendations.

We have wood floors with radient heat. tiled bathroom floors.