I am about to redo concrete floors in a bathroom and want to put down pex tubing in preparation for future solar radiant heat. I don't know yet if it should be tied into a future whole-house solar water heating or if the floor heating should be a small separate system. At this point we are just talking about a large bathroom, but I'd like to expand to an adjacent couple of rooms when we get ready to change those floors. Any advice on such a piecemeal process? If I do a separate solar water heating system for domestic water in the future (solar preheating of water before storage in existing electric tanks), couldn't the floor heating system be a very simple setup with a closed loop with no heat exchanger? Just the tubing going from the collectors to the floor and back? The collector would be very basic, just some pipes in a black-painted box. My main question would then be, what elements would be required in such a loop? I haven't finished researching this, but I'm thinking: - air release valve and expansion tank at the highest point of the system. - centrifugal circulator pump - some kind of pump controller, thermostat or switch - return manifold - zone manifold to turn of a zone, for example if a towel warmer would be on a separate zone. - 5/8" pex tubing with 10% polypropolene glycol in the water - collector: Any advice on the materials or size? Please advise if you think I'm missing something. What to do about the system in summer? Can I just cover up the panel? I believe if the collector is mounted somewhat vertically, the summer heat gain would be neglectable, and the system could be left on year round. I've understood that the water shouldn't be hotter than 150ðF, if that happens, what should be done? Or is that what the expansion tank is for?

With fiberglass insulation you need an air barrier more than the kraft faced paper in my opinion to keep the air from moving. I had an area in my basement that was a conventional wall 3-4 feet high and 30 feet long with just insulation and the basement was a freezer through the winter until I covered it with drywall. Fiberglass insulation has a very poor insulating factor if air can move through it. You need to create a barrier from the air inside the house to the air in the wall and the outside air.

Quick follow up: We have Natural Gas - we are planning on using a Polaris condensing tank water heater for both the domestic hot water and the heat source for the Hydronic in floor heat. We will use a heat exchanger. Currently we are looking at 1 zone for downstairs with 5 circuits or loops. If we did go with radiant hydronic baseboards upstairs there are 3 walls under windows that would never have furniture on them. Also, I thought it might be possible to run the 3 baseboards upstairs as separate zones with pex, then if we wanted to upgrade to under-floor heat in the future we could do so pretty easily...we are planning for a floating floor upstairs (laminate or engineered)

Do you need ROOM heat or do you want "warm toes"? If you need to heat the entire house using in-floor radiant heat (I'm assuming you are going with hydronic?) then the best option is always concrete, tile or stone. They offer the least resistance which means the most amount of heat pours through them and into the house. If you want warm feet (because the rest of the house is being heated by a fully operational forced air or baseboard heat system) then you can have engineered hardwood as a lovely option. There are SOME engineered hardwood floors that allow it being used over hydronic in-floor radiant heat....but do NOT count on it being "OK" with every engineered product you look at. And if you go with hardwood, you do NOT want to used underlayment or soft underpad with the heating system. The underpad will block quite a bit of the heat, creating excess load on your heat system (in essence you are heating the pad under the floor while the room remains chilly). Carpet is an amazing product when used with in-floor radiant heat. Carpet breathes nicely. And the underpad is the thing that has to have the "hydronic heating" allowance which means you can choose the pad that is best suited for your situation. The other thing to be aware of with wood and in-floor radiant heat: low humidity. In-floor radiant heat is KNOWN to dry out wood flooring products. Because the wood is SOOOO close to the elements, the first thing that heats up (and dries out) is the wood. To combat this issue, you MUST add in humidity control in the home. That means you will need a system (separate from the heating system) that has the ability to add/subtract humidity throughout the year. In Montana the outdoor humidity is often very low to begin with. If you then decrease it even more with a dry heat, then the interior humidity levels can be extremely low. And wood does NOT like that. A wood floor requires humidity to "sit" around about 45% all year round. Please check your building specifications to find out HOW you are going to add that humidity to your home. And then find out if you have the ability to change the humidity levels with the touch of a button (humidistat). This usually involves a system with heating/cooling ducts so that moisture can be added to the air in an even way... For right now, I would assume you HAVE to go with tile/stone/concrete until you find out the HVAC humidity control system that is currently in place for your build.