Within the IGSHPA closed loop design standards manual for pipe placement, section 2a.4, calls for buried GHP piping containing antifreeze and passing within 5' of any wall, structure or water pipe shall be insulated with minimum R2 closed cell. I am assuming this is because of possibility of surrounding ground formation freezing having an effect on these "structures" as result of the GHP temps going below 32? Which then may destabilize the structure, like a foundation footing? Within the IGSHPA closed loop install guide, for sizing and design, is stated that trench length is reduced as multiple pipes are installed in single trench. Within example #3 on page 76 I notice a ratio of 4 pipe/ft per foot of pipe or 225 trench/ft per 900 pipe/ft. As there is no 12" pipe separation inside trench for slinky install I wonder where I may find the applicable rule for trench reduction per coil? If there is one?