I have hydronic radiant heat attached under the subfloor with engineered wood and tile finish flooring, with three zones for the main living area of the house. Our original HVAC contractor primarily does forced air systems. His system resulted in on/off cycling of a single circulating pump. We grew tired of the hot/cold spots and the constant creaking from expansion/contraction. A few years after construction I met a contractor that primarily does radiant heat. He changed our system from a single pump to individual circulating pumps for each zone. (I have a total of eight zones) The individual pumps continuously circulate the water while the zone valves meter hot water as required to maintain a constant temperature. He also grouped zones by concrete or wood subfloor, so that I have even more control. As a result, our floors do not experience temperature swings with the resultant creaking from expansion/contraction. Our construction manager used our original HVAC contractor when adding a large addition. He too had problems with temperature swings, and has since had to modify the original system. I have a customer with an older home that has radiant tubing in his concrete foundation and has carpeting throughout much of the house. As a result, it may not be the most efficent, but you sure enjoy walking barefoot in their house on a cold day! I would recommend anyone that would like the comfort of hydronic radiant heat to work with a contractor who specializes in radiant heat. The concepts are simple, but the devil is in the design and the controls used.

Generally a north/south orientation for your long axis... if you have a lot of just morning or just late afternoon/evening sun; you might orient several degrees that direction. If doing a walipini, you dig to put your long axis generally east-west, as in northern hemisphere you bank your north side and angle to the south. Again, if you have a lot of just morning or just late afternoon sun, you might offset several degrees into your best sun. If the greenhouse is attached to the side of your house (more like a green room or a passive solar collector, south to southwest is preferable. Always temper to your protecting from your prevalent cold season/bad weather wind directions. Don't be afraid to put up windbreaks. Here I tend to shelter from NNW to NNE wind directions as that is our worst winter. We will get a few weird ones from the SW in like March, I have erected temporary windbreak from sinking steel fenceposts, putting a metal garden fence (2x4" holes 4' high) onto those posts, then putting a cheap blue tarp over the fencing and wiring down so no flap and burying bottom edge or concrete blocks.. Arced into the wind, the lee side being cupped to my greenhouse or cold frame; will do a great deal on keeping temperature inside. I can take it down later as needed.

What is your application? If it is a remodel without pre-existing radiant heating installed then most would use electrical for a bathroom or other small area for comfort versus heating. If it is new construction or a replacement system, then you would use a standard radiant heating system with a 'boiler' type unit that can be powered by solar, geothermal, gas, etc. Whether it can be used under hardwood floors depends on the hardwood flooring material. You would not use an electrical "mat" for whole house primary heating - it is simply for foot comfort.

All good advise. Climbing under the existing subfloor and installing a hydronic system is an option. Just make sure you insulate properly. Those systems are generally not super efficient and inadequate insulation will make matters worse. That said, it is very common and it can be effective. And in this situation, it may be your best option. We sell a product (Warmboard-S) which installs directly over TJIs/Joists. You could rip out the subfloor in the kitchen and install our product. This could be problematic and incur more costs than you're comfortable with, but it would get you a radiant heating system and get your floor height issues resolved. Our Warmboard-R product can install over that subfloor and you would gain under an inch of floor height – but that won't solve the inconsistent floor heights. Sounds like a rough situation. If you need this done quickly, another option would be to opt-out of the radiant in the kitchen and try to get the builder to provide some benefit elsewhere in the house in it's place.