I have an outdoor wood heated water stove with a pump to circulate the hot water to my house regulated by a thermostat in the house. I'm wondering about using hot water from my water stove to also heat a cold frame (which is basically a box with glass on top, big enough to hold some flats of pepper plants). I'd like to have a cold frame about 3'x12' (very roughly). If I want to keep a box that's insulated on the bottom and sides but with old storm windows simply laid across the top and an insulated blanket over the glass top every night at around 80-85 degrees through the night and on rainy days starting in March when nighttime lows can drop as low as 20-25 degrees with daytime highs as low as 40 but averaging more like 40 at night and 60 during the day and then continue using this cold frame until mid-May, can anyone recommend a relatively cheap and easy way or give me any advice on what kind of tubing to use to radiate heat below my pepper flats, how much of it to use, and ways to regulate the temperature in the cold frame? I have 3/4" pex running to my house that I would presumably T off of, and the water temperature can vary between 120 and pretty close to boiling.