DESIGN

How a Frost Heave Floor Is Designed

Heat cable, laid to heat the ground — not the floor

Heat cable frost heave systems provide better monitoring and control, with less maintenance than air or glycol systems. Self-regulating heat cable automatically adjusts wattage as temperatures change, always providing the correct output to maintain 50°F.

The cable is designed to heat the ground — not the freezer floor itself. Freezers pull heat out of the ground below them continuously; the cable simply replaces what's being pulled out, holding the subgrade above freezing indefinitely.

How the Freezer Floor Heating System Is Installed

Subgrade / base A prepared base or hard-packed substrate supports the heating system.
Heating conduit 3/4" rigid conduit is installed within the substrate according to the layout, backfilled with aggregate or a mud slab — rock, gravel, sand, or any non‑insulating fill material — with a minimum 1" between the conduit and insulation.
Heat cable Self-regulating electric heat cable runs through the conduit, providing heat to the subgrade and automatically adjusting wattage as temperatures change.
Insulation 2 layers of high-density insulation, joints staggered, installed above the heated substrate to reduce heat loss toward the freezer.
Vapor barrier Minimum 6 mil vapor barrier, joints overlapped 12".
Top slab Install top slab per structural requirements.

Isometric cutaway drawing of typical freezer floor construction showing top slab, rigid foam insulation, vapor barrier, mud slab, and embedded conduit — Click to open the full drawing

Complete Freezer Floor Heating System Design

Thermalinc does considerably more than sell heat cable. From the initial layout through the finished control panel, we provide the design work a project actually needs:

Heat cable sizing
Conduit layout
Cable spacing recommendations
Electrical load calculations
Circuit layout
Temperature sensor placement
Control panel design
GFI/GFEP protection
Alarm and monitoring
Wiring diagrams
Installation documentation
Application assistance

Heat Load Sizing

Approximate watts per linear foot of cable, by freezer temperature, insulation thickness, and cable spacing. Actual heat load is calculated per project.

4" Insulation
Freezer Temp	Watts @ 2 ft	Watts @ 3 ft	Watts @ 4 ft
−40°F	6.4	7.3	9.1
−20°F	4.1	5.1	7.0
−10°F	3.6	4.3	5.5
0°F	3.2	4.0	4.8
10°F	2.7	3.0	3.4

6" Insulation
Freezer Temp	Watts @ 2 ft	Watts @ 3 ft	Watts @ 4 ft
−40°F	3.9	5.2	7.0
−20°F	3.2	3.7	4.9
−10°F	2.7	3.0	4.0
0°F	2.3	2.7	3.2
10°F	1.8	2.1	2.4

Why conduit spacing matters. Spacing wider than 4 feet can allow “striping” — narrow frozen bands of ground between adjacent runs — even when the cable itself is correctly sized. We hold to a 4-foot maximum standard for this reason, occasionally extending to 50 inches on 0°F and warmer freezers, where the heat transfer margin allows it.

Spacing of 5 to 8 feet, sometimes used in the industry to reduce cable footage and cost, but does not transfer enough heat to prevent striping between runs — and has been linked to cracked, heaved floors and significant structural damage. Proper spacing is a heat transfer and heat loss calculation, not just a watts-per-foot or watts-loss consideration.

How does heat cable compare to a hydronic glycol system?
See our full side-by-side comparison — system components, failure points for each approach, and the protection and monitoring built into Thermalinc's electric heat cable system. Read the full comparison →

Back to the overview.
This is one piece of the full freezer floor frost heave prevention system. Back to Freezer Floor Frost Heave Prevention →