Proper way to insulate basement slab for radiant heat?
We will be pouring the basement floor next week, and I am getting conflicting information on the best way to insulate under the slab.
I had a very reputable source tell me that it is actually cheaper to heat a floor that has no insulation under it, because using the ground for heat storage actually causes less run time on the pump over a course of time. He stated that while the pump runs initially longer to heat the slab/ground beneath it, with all that storage you have longer intervals between runs. He also stated with an insulated floor (2" foam) the run times are shorter due to the insulation, but are more frequent because it heats up just the concrete, shuts off, cools down quicker, starts up again, etc.
I was also told that the 2" foam was the only way to go, nothing less. I need to get this nailed down by next week.
Any help/input is appreciated.