Run a test- if you keep it at 30C for a week in a test-oven that has a bit of ventilation to allow the vapors to escape, does it still stink? (I suspect the bulk of the VOCs will boil off in the first 24 hours, but you MIGHT still be able to smell it faintly after a week.) But no matter what, unless you're air-conditioning the place you're likely to find out on the hottest week of the summer anyway, eh? By the end of a heating season (or even a heating-week) the issue will probably be much abated, but building a simple test oven (a cardboard box with a thermometer, a sample and a low-wattage light bulb will probably do- add enough holes to allow air movement, tape up some of the holes if the temperature falls too low) and testing a sample may give you the real answer sooner.

Looking at it another way, the VOCs are going to come out eventually (whether you smell them or not)- heat-treating them will boil it off sooner. You can actively ventilate any time your nose-alarm goes off, and you'll be able to tell when to back off on the ventilation.

Hydronic heating water temps are far below the kindling temperature of any building materials, and RADIANT heating temps are quite a bit below that- not to worry on that front, but really, warm floors are preferable to radiant-ceilings by far. (Warm head, cold feet still feels cold, but not conversely.)

BTW: What do you intend to use as a boiler? 17K is a VERY small design-day load (it's about the lowest modulated output of any of the modulating-condensing boilers.) Your annual water-heating load may very well exceed your space-heating load, making a combi-system of some sort the best option.

Thanks for the feedback Dana. Doing another test is a good idea. Dan Holohan's "Hydronic Radiant Heating" book says "the stench stays with you for a long, long time". Maybe each brand is different, so it's worth doing a longer test. BTW we're not talking VOCs here, as far as I can tell from the MSDS sheets I've looked at anyway. Just an odor that we'd rather not have!

I've gotten some other feedback that says the temperature isn't a concern with the paper backed insulation, which is reassuring. I guess the inspector will have the final say...

Have you had bad experiences with ceiling radiant? With respect, I'm actually becoming fairly comfortable with the idea of radiant ceiling after spending hours checking out forums, books, websites and a study that is unfortunately too big to attach. The temperatures from floor to ceiling, if the system is done well, are apparently pretty even (much better than forced air). Also, my floor system (theoretically) isn't ideal: 1.5-2" of wood to heat through, more difficult installation, area rugs, slower response, tubing would have run under lots of furniture and cabinets, wood flooring being sensitive to temp changes, etc. I might mix it up and have a few rooms with ceiling heat, a few with floor (no asphalt paper in those), and concrete slab in the basement. Could be interesting.

I haven't decided on a boiler yet, but I think the combi system does make the most sense. It'll need to be an electric system, not gas (cheap hydro rates here).  Any suggestions?? I've got 200amp service. I've looked at some of the electric boiler companies and indirect tank, and also Seisco tankless, but nothing has really stood out, and I don't have much to go on. I'm also planning to have solar preheating - cold winters but lots of sun here.

Roger

If you are already planning to run solar, make the solar store your DHW tank, and spend your thinking/designing time on the solar system- the efficiency of the electric DHW heating will be pretty similar no matter what method you use (unless you spring for heat-pump versions like they have in Japan.)  Many/most solar storage tanks come pre-fitted with electric backup (or ports where they can be installed), multiple heat-exchangers, etc.  As a HW heater you won't find any simple hot-water tank heaters better insulated than a solar storage tank- your standby losses will be quite low.  If your radiation is designed to deliver design-day heat at 120-140F (typical for staple-up radiant in a well insulated house), that's the temp you'll be needing for hot water anyway- it simplifies the system design.

If winters are especially cold you're probably better off using evacuated tubes instead of flat panels.  If it's snowy, you may consider mounting the array vertically (or steeper than 70 degrees) to ensure that the tubes will shed snow.  The winter-time performance  hit from such steep mount is low, (VERY low compared to snow covered tubes!), and in the summer & shoulder seasons  you will be needing to dump heat anyway to keep below the boiling point.  Running the collectors at full-temp heat won't be quite as efficient as a low temp DHW preheat, but with evacuated tubes it's not bad.  A good solar designer should be able to determine where the tradeoffs are.

My only experience with radiant ceilings was with electric resistance heating radiant.  It worked OK where the floors were carpeted, but in the tile-floored rooms it would have been much better to have had the heaters in the floor.

I do have a designer that will help with the details of the solar and the heat source, but I'm really interested in more opinions. Dana are you suggesting using a large solar storage tank beefed up with extra elements (around 12kw) as the DHW tank and heating the radiant off of a heat exchanger inside that tank? One concern I have about the specially designed solar storage tanks is that they have the solar HX wrapped around the outside of the tank, which seems counterintuitive to me. Would that design really be as effective as having an internal HX?

Our winters aren't that cold but we get lots of snow - sometimes 4-6 ft in the yard by February. Most people are mounting tubes around here, but they are putting them on the roof, which I think is asking for headaches. I'd like to mount tubes in the back yard so I can clear and maintain, and possibly angle adjust them. I'm not catching what you meant by "Running the collectors at full-temp heat won't be quite as efficient as a low temp DHW preheat, but with evacuated tubes it's not bad." Do you mean that using the large tank solely for solar preheating and a second high temp tank for DHW and radiant might be more efficient (but more expensive)?

Hello Roger,

I have used Radiant ceiling heating and it is the best choice I have made. The radiant ceiling heat when properly installed and insulated will heat everything in the room. After having a heat loss calculation done I was able to see how many watts where needed to efficiently heat my rooms. I did not have to fill the entire ceiling with electric elements because my heat loss was reletively low. I live in MA so our winters are mighty cold and the ceiling heat works great. Also a plus is that it cuts down on the contaminates that float around the room. Having allergies this is great for me. I also find that floor is warm because the electric radiant heat is acting like the sun and warming everything in the rooms like the sun does.

I hope this is helpful for you.

In that case, and taking into consideration the low heat load of 17k, I think you should look at electric cable for the radiant heat. Why buy equipment to heat water when the cable will give you nearly 100% efficient energy conversion right off the bat? At 17k you may very well find your TV, computer, cook stove, body, etc., will supply most of that heat so there may be almost no need for a heating system! 17k converts to about 5000 watts. That's less than 25 amps at 220 volts, not much load at all for a 200 amp service.

Focus your solar heating efforts toward DHW. I would guess that's where your greatest energy consumption is going to be.