Radiant heat question

I'm sure that any coating will be an insulating barrier but to what extent? I don't know. If you do choose trim coil I can say that the stuff I bought at Home Depot had just barely enough paint to color it.
Why don't you want plates? If you're planning on using long sections of material I can tell you that you will have some problems with expansion. They will be talking to you with each temperature change. They may even work themselves loose from the subfloor.

I agree the thin flashing thickness plates do not grab the tube well, and have a tendency to expand and contract causing "oil canning" noise or ticking sounds. Outdoor reset controls help limit the temperature swings somewhat.

Towards the end Wirsbo suggested nailing only one side of those thin plates so they could expand and move with less noise. Not much of a transfer product with one side hanging

If your load in BTU/ square foot is low consider suspended tube with UltraFin type plates.

I wasn't disparaging plates. In fact I used them on my staple up and they have served me well. I was just stating that long sections of aluminum, a material that has one of the highest coefficient of thermal expansion would not be the right choice in this application. As long as the plates are fully annealed and they are spaced away from each other when installed, they are quite silent.

I personally wouldn't go longer than 16 inches on my plates. I don't have the numbers off the top of my head but 36 inches would expand a lot and probably make quite a bit of noise as well as working itself loose. I got my plates from the company below and formed them with a length of pex nailed to a 2x4 and laying the plate on another piece of wood with a slot cut in it then used a 9 pound sledge hammer to drive the tube into the slot.
I http://www.radiantcompany.com/?referrer=google&gclid=CJWw24uo2coCFc4YHwodEE0L9g

I have eight hundred feet of 4 and 8 foot Thermofin heavy aluminum plates underfloor.
I secured them every 16 inches or so on both sides of the plate with self piercing truss head screws.
About four inches of space between plates because that was easy to align with a piece of scrap tube when installing them.
Minimum water temperature is 70, max is 140, constant circulation.

They are into their third heating season, and there has not been a single noise from any of them.
The whisper quiet Grundfos Alpha pumps make more noise.

The coefficient of thermal expansion of aluminum is about 0.000013 inches per inch per °F.
Assume you have a 100 degree temperature swing.
Assume your plates are 36 inches long
0.000013 in/in/°F * 100°F * 36 in = 0.0468 inches
That's less than 1/16 inch total expansion in this scenario. Adjust the numbers for your particulars.

Tightly secure the plates with truss head screws or some other wide head fastener every eight inches and the expansion between screws works out to about 0.010 inch - about the thickness of two sheets of paper. Maybe consider using a plastic washer under the fastener head if you are real concerned about oil canning and noise.

As Mr. Rohr mentioned, if you can incorporate outdoor reset and constant pumping that will eliminate the frequent wide temperature swings and the associated expansion and contraction.

Take a look at this!

http://www.amazon.com/gp/product/B0..._m=ATVPDKIKX0DER&pf_rd_r=0HZG5B4FJDNBP5QJYERJ