do not use copper for tubing , some effects with the co2. Roots do not absorb co2 so thats out.
NOw putting the co2 in the room at given levels 1500 ppm works great.
Gas's going to a lower pressure usualy get cold.
Now when venting in to the room its best to use a sub blower to get it all over and vertical fans to get it off the floor. Note any leaks at the door levels , with out a good seal it just flows out a a very good rate.
See pictures in my gallery, for solonide and wiring