If Thermal Track is made by a couple of companies, that explains it. The brochure I have shows an aluminum face and their recommended installation for tile is cement backer board over the Thermal Track, then an iso membrane on that and tiling on the membrane. Warmboard itself does "allow" you to thinset Ditra directly to the Warmboard, but Schluter won't warranty an installation like that. Schluter recommends a transition material between the Warmboard and the Ditra. Warmboard used to have a bit of double-speak on their website and in their literature. Not sure if they are still that way. They first tell you to install in accordance with TCNA guidelines, etc, or IAW the manufacturer's instructions, etc, but then they give you shortcuts around those guidelines and say "they've never heard of a failed installation" when taking those shortcuts. For those not familiar, the big difference between Warmboard and Thermal Track is that Warmboard in an of itself is a structural subfloor and radiant track combined into one material. Thermal track is installed over an existing subfloor. I installed Warmboard when it first came out. Nice product, but not worth the $$$ or added steps required during installation or in protecting it after the installation. At least not in my book. Mongo

The good news is that neither heat nor cold have an effect on wood movement. The bad news is that moisture content does. Is this a genuine wood floor or one of the manufactured floors? If manufactured, I'd consult the manufacturer's literature. If natural wood, each species shrinks and gains on an individual basis. If plywood, with a veneer, the movement is less. But that would be a manufactured floor, which the manufacturer would be able to answer that. If genuine wood, your floor would be constantly moving, just like genuine wood moves in your house from summer to winter. If the wood had a Summer moisture content of 11% in the East when installed, and was reduced to 6% during the Winter, you would get shrinkages of possibly 1/8" per foot of width. If installed in the dry Winter, the wood would expand in the Summer unless your house was perfectly climate controlled, resulting in buckling. Wood improperly secured that doesn't allow for movement will eventually crack. Properly secured, it should fare well. Since heat dries the air, and dry air causes wood to shrink, your floor might move around. I'll have to ask around about this at work and get some other opinions.

The ell of our house with kitchen, pantry and dining room has radiant floor heat. It has its own thermostat and several loops feeding off one manifold. We don't change the heat there over the short term. We might turn it down if we will be gone for a week, but we don't change it over the short term. In our baseboard heat in the rest of the house , the radiators change the heat fairly quickly since the water directly heats the air, but the radiant floor heat first has to raise the temperature of the floor and then the floor raises the temperature of the air above it, so it's a much slower process. I don't find that the rooms heat more than a degree above or below the set temperature. With 3 windows and high ceilings, you have a large air mass with heat loss through the windows, so your time to heat the bathroom from a lower temperature will always be long. To my mind, it makes the most sense to keep the bathroom temperature at whatever heat you like and leave it there. It's the nature of radiant floor heat to be easier to maintain temperature than to quickly change temperature.

Since you have chosen warmboard over gypcrete, what was your reasoning behind it besides responsiveness? I am sorry for the confusion. I didn't build a house with Warmboard, I had it in a house where original owner had installed it. It wasn't a house I built. I used it in the sense that I heated the house with it. I looked at the Gypcrete system and somehow feels uneasy about it. Doing a concrete pour over first and second floor does not sound structurally sound to me. Gypcrete has positives and negatives but shouldn't be overlooked because of structurally sound. I think a competent and knowledgeable designer is much more important than which type of system you use. So if you don't have a lot of experienced local people, you have to find experienced people who can help design at a distance. I would start with Radiant Engineering (talk to many companies though). A long somewhat unbiased discussion of radiant: First, it should be noted that radiant heat isn't an efficiency discussion. As people have pointed out many times hydronic radiant systems rarely have a positive payback. They are simply too expensive to install and they never payback if you are installing central air. However, every decision in your house isn't about payback. There are many decisions, such as paint color, cabinet color, cabinet design, many fixtures, etc., that are about your enjoyment of your home. No one has a pool installed because they want it to add value to their house. Radiant fits soundly into that category. Next: A discussion of trade-offs between the different systems. It is important to note that ALL radiant floor systems will provide a comfortable environment to a home that other heating methods struggle to achieve. There are basically five considerations in radiant heat (1) installation costs, (2) operating costs, (3) responsiveness (4) allowable customization and (5) noise (as hot water passes through cold aluminum plates it makes noise). If we look at the different systems we can typically see how they handle each of these things. Warmboard is (1) very expensive to install, (2) it has a low operating cost as it is a warm water system rather than a hot water system, (3) incredibly responsive for radiant heat (able to heat a structure in hours rather than days), (4) low customization and (5) low noise. Underfloor transfer plate systems are (1) moderately expensive to install, (2) low operating costs as they are also warm rather than hot water systems, (3) are somewhat responsive (4) highly customizable and (5) have more expansion noise. Gypcrete overpour is (1) moderately expensive (still cheaper than the two above), (2) have low costs as,they too are warm water systems, (3) not responsive at all, (4) are highly customizable and (5) eliminate almost all noise. Staple up systems are (1) pretty cheap (2) high operating costs as they are a hot water system, (3) not responsive at all, (4) limited customization (they are more limited by physics than design), and (5) are pretty noisy. So looking at Warmboard vs. similar systems - the only real concern from using any aluminum covered plywood system is the noise. Warmboard eliminates expansion noise because of the "special" glue they use to adhere the aluminum to the wood. I can't really tell you how special their glue is, I feel confident they will say super special and their competition will disagree. Warmboard type systems vs. underfloor transfer plate systems - Warmboard is quieter but the loops are not really customizable. Loops are 8" apart with Warmboard, so you can choose not to put warmboard in places but you can't get the loops closer together. With transfer plate systems you can customize the heat of a room by simply moving the loops closer together. This means that you can make the floor right outside the shower warmer than the floor beside the toilet (not many people spend a lot of time standing beside their toilet), but there is more expansion noise. Warmboard is a bit more responsive than transfer plates. Warmboard vs, gypcrete overpour - Gypcrete overpour gives you almost unlimited customization without the noise associated with aluminum transfer plate systems. However, it is not at all responsive. Staple up systems - They are more expensive to operate than any of the above systems but are cheaper to install and easier to maintain. You are not likely to nail through a staple up system with a nice thick transfer plate. Also easier to remodel with staple up systems. TL:DR In the end, if I was ranking a radiant system today - I would probably rank it - underfloor transfer plates > gypcrete > Warmboard. But it is a three way photo finish so it wouldn't take a lot to change the order. Also noisy houses don't bother me at all.