I have the kind where they are toghether then wraped in silver bubble wrap and burried 3 feet down.
minus 25c and no sign of snow melting on the tube where it exits the boiler and goes into the ground.
the best way of doing it is this ....1 inch pipe of your choice i used wirsbo cause i like that if frozen it will not burst or pex with 02 barrier but its hard to work with as it has metal inside and if you kink it your done.
then you take the pipe and lay it into 8 inch square styrofoam pieces that have channels cut out.
then tape it every 2 feet and after its all taped wrap it in poly and if you want run a bead of silacone
I say this way cause you can get pipe for around $200 for 300 ft and the styrofoam pieces for $10 for an 8 foot piece.
so a 150 ft run would cost you $200 for pipe $200for strofoam pieces and $100 for poly and some tape.
this way is the most cost effective way and by far the best for insulation.
if ground water is a problem i say use premade from central at $15 a foot
I am no expert but i have installed my system and it has been the hardest thing i have ever went through in my life as far as heating .
email me at bassman(at)sasktel.net if you want pics or need more info .
keep in mind plumbers dont work with 1 inch so fittings are hard to find and when you do you need tools to expand pipe ect .
good luck
shayne