My Thermopex is 8 to 10" down. Just deep enough so I don't bother it when I drive over it with my truck and trailer. Zero snow melt. It's been in almost 6 years.
My CB ThermoPex is buried about 24" and wrapped in utility sand. 70' run to house. No temp difference from OWB to house yet the ground around the pipe does not really freeze.
Thermopex, no more than 24" deep.
My runs are : 250' to house, 125' to shop, with little or zero heat loss, & no melting snow on top. The last 6 feet to the house is above ground & under the decking.
Do it right & spend the $$ on good pipe, forget about insulating yourself.
I love NOT giving 5 grand++ a year to the oil company!