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...

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.

We installed floor heating in our master bath remodel this summer. We have programmed the system and it's already making cooler mornings more pleasant on the feet. And we live in GA... I lived much of my life in western Europe and the U.S. midwest, so I know cold. Adding the radiant heat cost about $1100 for us (kit, extra floor sensor, and labor), which was about 6% of the project cost. I just really hate cold floors in the morning, so I think it will be worth it.

Sounds like you live in one of those rare climates where radiant floor heating makes sense financially. It is one of the most efficient ways to heat but as live wire points out, if you are including any type of AC or heat pump for cooling, then the upgrade to radiant is probably more of a luxury add-on whose cost effectiveness is very much in question. Sounds like forced-air is still cheaper overall than radiant in your area. Radiant floor heating is less comfortable than forced-air for homes that meet international code levels of thermal performance. If you can feel the heat of a radiant floor by touch, it suggests the building envelope was not proven airtight with a blower door test and probably does not have adequate levels of insulation and fenestration performance. Thermostat response delay or lag time is the reason forced-air is arguably more comfortable than radiant. Outdoor temperature, mood, state-of-rest and other occupant dynamics benefit from quick thermostat response. Radiant floors respond slowly to changes in thermostat. Don't base your experiences of forced-air heating on older, inefficient homes. A home built to international code minimum performance has very low CFM (airflow) requirements. A professionally designed and installed forced-air system results in operation that is barely noticeable. Hire a third party certifier, like energystar to verify your home is designed to meet international code minimums and upgrade to have a Manual J calculation by this third party certifier. The nice thing about energystar is that an outside party will be verifying your home is built to minimum standards and that the HVAC system is installed appropriately. It's also important to choose a builder who is comfortable with this process of checks and balance. It sounds like healthy Indoor Air Quality IAQ is important to your goals as it should be. I would argue that forced-air can be better for dust control because it offers the opportunity to use filters to capture dust in your indoor-air, dust that is present whether you have radiant or not. Most people's problems result from poor construction protection and not having filters at return grills. Filters can reduce dust but should not be the primary strategy for IAQ. Outdoor-air ventilation is the best way of ensuring healthy indoor-air and most systems rely on some amount of ductwork. Using a third party certifier is a great way to ensure these systems are installed and commissioned in an appropriate manner, as most programs are following ASHRAE 62.2 minimum ventilation rates. Eliminating attached garages, vented crawlspaces and indoor combustion appliances are more important for indoor-air quality than any concerns of radiant vs forced-air.