Thanks David. Being precise and listing every point and sub point is tricky. English was my worst subject in school, I'm better at building bathrooms than building paragraphs. I work harder posting more information but like you mentioned everyone needs to dig deeper, find all the questions that need answering and then go about finding the correct answers and then confirming the source of the answer. I have spoken with my supplier and received info back from them direct, I then worked out my own math to confirm and then double check the Heat Loss table. We adjust the cable spacing only a little to try and fudge out dips and valleys. And never bring the cable in closer than spec'd. Again, I'll post my math and equations with as much detail as I can provide so people can understand the process I use to work out these calculations. I build stuff every day, I read and hone my skills everyday and I work with pros everyday. I have learned a lot and which each new project there is always the "X" factor. Your gut can tell you when something just doesn't look right and inspectors should be shown what your doing and not left out of the loop. We have a great group of men and women checking our projects here in Vancouver, get to know your local inspectors - it's worth it. My building inspector left my home raving about it yesterday - he went on to say it should be entered in a contest and hopes he gets to come back for the final so he can see my home completed. These are not monsters or people to avoid- they are your last double check on your project and honestly speaking you should be the last check on any project. It's your project - don't trust anyones opinion as fact. Work it out yourself or spend your time finding the right contractor. There are many guys out there who know what their doing, take out permits and do the job right. That said they seem to be the minority...

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

Not an expert-- still working on these issues myself-- but I think that with gypcrete below and engineered wood above, you could have pretty much any underlay you want without worrying. You are getting great efficiancy from the choices you've already made, and the underlay is such a [relatively] small part of the equation that it won't be a problem.

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.