Should I insulate underneath my snow-melting system?

Insulating under a snow-melting system will improve the efficiency of the system.

Adding insulation both under a slab and near its exposed edges reduces heat loss into the ground and allows the slab to heat more quickly, which lowers total operating costs.

In general, most insulation is done with rigid polystyrene foam 1 to 2 inches thick. However, your best source of information is your concrete contractor. Consult with them if insulation is allowed by code or in your application (e.g., load-bearing cars), and what type and thickness to use.