In floor radiant heating in greenhouse
I am a newbie here and I didn't find too much already posted and discussed on this. I am building my dream greenhouse this year and have planned a freestanding 12' x 20' structure. I plan to heavily insulate the north and parts of the east and west walls, and use 5 wall polycarbonate on the rest. My goal is to grow in this greenhouse year round in zone 3, where recently we didn't see positive temperatures for over a week straight. I plan to excavate, insulate, lay 3 layers of coils separated by about 6" in sand under the structure and circulate heated fluid, likely heated by either gas or electric water heater. I plan to install raised beds to grow in, for both starting seedlings and growing veggies year round. Has anyone done this already, and did it heat adequately in cold temps?