Quote:
Originally Posted by DickR
There is always deep ground heat being conducted by the soil upward toward the cold air in winter. In the summer the reverse is true. That's why deep ground temperature is fairly uniform below say 6-8 feet down; that temperature reflects the average air temperature over decades. Thus the hay bales, providing insulation, will let deep ground heat increase the temperature up toward the surface. Actually, if the hay is wet, bacterial action within it generates some heat as well. If you've ever gone by a landscaping company's piles of wood chips or bark mulch, just after a loader has dug into the pile and exposed the pile below the old surface, you may notice the pile steaming in the cold air. It's warm in there!
As a more permanent solution, if the ultimate problem turns out to be the line not buried sufficiently deep below the driveway, the soil over the pipe could be excavated, creating a trench about four feet wide. A layer of rigid XPS foam board would then be placed over the pipe and the trench backfilled (and the asphalt patched). From one site on the subject of Frost Protected Shallow Foundations: "Soil has an insulating value ranging between R-1 per foot and R-3 per foot. (Yes, these values are in feet, not inches.) An inch of polystyrene insulation, R-4.5, has an equivalent R-value of about 4 feet of soil on average.
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I have heard the same thing as well Dick. I have known people who have had to do just what you said with the 2" green foam.
Driving over the driveway especially gravel ones tends to drive the frost down deeper. That is why they say never drive a snowmobile over your septic or leach field during the winter as it will drive the frost down deeper into the ground and could cause it to freeze.