1 Scope

NOTE This Standard covers the design, specification, and installation of embedded radiant snow and ice melting systems in outdoor hardscape surfaces, including pedestrian walkways, entry plazas, ramps, accessible routes, vehicular drives and aprons, and loading-dock approaches. (1.1)

NOTE Two technology types are covered: hydronic systems that circulate a glycol/water mixture through embedded PEX or PE-RT tubing connected to a dedicated heating plant or the building hydronic system, and electric resistance systems that use embedded heating cable or factory-wired heating mats. (1.2)

NOTE Also covered are automatic snow and pavement sensing controls with manual override, glycol fill and make-up provisions, heat exchangers where the loop connects to the main building system, circuit manifolds, and slab expansion provisions at the heated assembly. (1.3)

NOTE This Standard applies to new construction and renovation in cold-climate regions where ice and snow accumulation on pedestrian or vehicular surfaces poses a safety risk or an operational requirement. (1.4)

NOTE The following are outside this Standard and are governed elsewhere: (1.5)

Roof, gutter, and downspout snow/ice removal and deicing heat tape — see Gutters And Downspouts for drainage context; exposed roof/gutter electric heat under NEC Article 426 is a distinct trade scope.
Hydronic distribution piping routed inside the building to reach a snow melt manifold — material, joining, pressure class, and main-system distribution belong to Hydronic Piping.
The primary hydronic heating plant — boilers, heat exchangers, pumps, and expansion tanks — that supplies the snow melt circuit — see Hydronic Piping and Hydronic Specialties.
Flushing, chemical treatment, and commissioning of the glycol loop — see Hydronic Cleaning And Flushing.
Electric heat tracing for freeze protection of water supply or drain piping — see Electric Heat Tracing.
Concrete flatwork mix design, finish, and jointing of the slabs that contain the tubing or cable — see Concrete Paving.
The below-slab vapor retarder under the heated slab assembly — see Vapor Barriers Under Slab.

NOTE A snow melt system is a life-safety and operational asset, not a comfort amenity; once tubing or cable is encased in concrete or asphalt it cannot be repaired, so design coordination, embedded-element protection, and pre-pour testing carry unusual weight in this scope. (1.6)

2 Referenced Standards

2.1Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.

2.2Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.

NOTE The adopted edition of the National Electrical Code varies by jurisdiction; the Contractor shall confirm the locally adopted NEC cycle before sizing electrical work. (2.3)

Standard	Title
NFPA 70 (NEC) Article 426	Fixed Outdoor Electric Deicing and Snow-Melting Equipment
NFPA 70 (NEC) 426.20	Embedded Deicing and Snow-Melting Equipment — Installation
NFPA 70 (NEC) 426.28	Ground-Fault Protection of Equipment
NFPA 70 (NEC) 210.20	Branch-Circuit Ratings — Overcurrent Protection and Continuous Loads
ASHRAE Handbook — HVAC Applications, Ch. 51 (2023)	Snow Melting and Freeze Protection
ASTM F876	Crosslinked Polyethylene (PEX) Tubing
ASTM F877	Crosslinked Polyethylene (PEX) Hot- and Cold-Water Distribution Systems
ASTM F2623	Polyethylene of Raised Temperature (PE-RT) SDR-9 Tubing
ASTM E814	Fire Tests of Penetration Firestop Systems
UL 515	Electric Resistance Heat Tracing for Commercial and Industrial Applications
UL 1673	Electric Floor Heating Cables

3 Submittals

NOTE Action Submittals (3.1)

3.1.1The Contractor shall submit the following action submittals for review before fabrication or installation:

Product data for tubing or heating cable/mat, manifolds, controls, sensors, glycol heat-transfer fluid, and insulation.
Shop drawings showing the tubing or cable layout, circuit boundaries, on-center spacing, manifold and sensor locations, slab edge and under-slab insulation extent, and expansion-joint and saw-cut joint locations overlaid on the snow melt layout.
Heat-load calculations per ASHRAE Handbook — HVAC Applications Chapter 51, identifying the design climate class, design surface output, and the resulting tubing spacing or watt density.
For electric systems, branch-circuit and panel schedules showing connected load, continuous-load sizing at 125%, and GFPE provisions.
For hydronic systems, the glycol type, concentration, and design freeze point, with the make-up, air-separation, and expansion provisions.

Action Submittalscheckbox

☐ Product data (tubing/cable, manifold, controls, sensors, fluid, insulation)

☐ Shop drawings (layout, spacing, manifold/sensor locations, joints overlaid)

☐ Heat-load calculations (ASHRAE Ch. 51, climate class, output)

☐ Electric branch-circuit and panel schedules (continuous load, GFPE)

☐ Hydronic glycol type/concentration and make-up/expansion provisions

NOTE Closeout Submittals (3.2)

3.2.1The Contractor shall submit the following closeout submittals before final acceptance:

Record drawings showing the as-installed tubing/cable routing, circuit identification, and sensor and manifold locations.
Documented results of the pre-pour pressure test (hydronic) or insulation-resistance test (electric), including the test held through the concrete placement.
Operation and maintenance manuals covering the control sequence, setpoints, glycol service, and seasonal startup/shutdown.
Manufacturer warranty documents for tubing/cable, controls, and heat-transfer fluid.

Closeout Submittalscheckbox

☐ Record drawings (as-installed routing, circuit IDs, sensor/manifold locations)

☐ Pressure / insulation-resistance test records (through concrete placement)

☐ Operation and maintenance manuals (sequence, setpoints, glycol service)

☐ Manufacturer warranty documents

NOTE Informational Submittals (3.3)

3.3.1The Contractor shall submit the following informational submittals:

Manufacturer installation instructions for the embedded elements and the substrate-specific listing where asphalt is used.
Qualification statements for the installer and, for electric systems, the licensed electrician of record.

Informational Submittalscheckbox

☐ Manufacturer installation instructions (and asphalt listing if applicable)

☐ Installer and electrician qualification statements

4 Quality Assurance

NOTE Installer Qualifications (4.1)

4.1.1Hydronic tubing loops shall be installed by an installer trained and certified by the tubing or manifold manufacturer for embedded snow melt installation.

4.1.2Electric heating cable and mat circuits shall be terminated and connected by a licensed electrician working under the manufacturer's installation instructions.

NOTE Source Quality (4.2)

4.2.1Heating cable and mats shall be listed under UL 1673 for embedded floor/pavement heating, or under UL 515 where supplied as heat-tracing-listed snow melt cable.

NOTE Where electric heating elements are installed in asphalt, the elements shall be listed by the manufacturer for asphalt embedment; cable not listed for asphalt shall not be used in asphalt. (4.2.2)

4.2.3PEX tubing shall comply with ASTM F876 and ASTM F877; PE-RT tubing shall comply with ASTM F2623.

NOTE Pre-Pour Coordination (4.3)

4.3.1A pre-pour coordination meeting between the snow melt installer, the concrete contractor, the electrical contractor (for electric systems), and the Engineer of Record shall be held before concrete placement.

NOTE Saw-cut and expansion-joint locations shall be reviewed against the tubing or cable layout at the coordination meeting; no joint shall be cut where it crosses an embedded loop or cable run. (4.3.2)

5 Environmental and Service Conditions

NOTE Design Climate Class (5.1)

NOTE The snow melt design shall be based on the ASHRAE climate class appropriate to the local snowfall intensity, wind exposure, and the surface's priority of service. (5.1.1)

NOTE Class I covers light snowfall and lower-priority surfaces; Class II covers moderate snowfall and standard commercial surfaces; Class III covers heavy snowfall, wind-exposed sites, and critical surfaces such as hospital entrances and accessible ramps. (5.1.2)

ASHRAE design climate classradio

○ Class I — light snowfall, lower priority

● Class II — moderate snowfall, standard commercial

○ Class III — heavy snowfall / wind-exposed / critical

NOTE Surface Priority (5.2)

NOTE Accessible routes, ramps, and the primary egress path from a building entrance shall be designed to the highest surface priority on the project, because residual ice on these surfaces presents a direct life-safety hazard. (5.2.1)

Surface priority of the heated arearadio

○ Critical (hospital entry, accessible ramp, primary egress)

● Standard commercial (walkways, plaza, entry apron)

○ Low priority (secondary walks, residential)

NOTE Design Surface Output (5.3)

NOTE The design surface output shall be calculated per ASHRAE Handbook — HVAC Applications Chapter 51 for the selected climate class, not assumed from a default watt density. (5.3.1)

NOTE For hydronic systems, surface output typically ranges from 80 to 125 Btu/hr·ft² for Class I, 125 to 200 Btu/hr·ft² for Class II, and 200 to 250 Btu/hr·ft² for Class III; commercial walks in Zones 4 to 6 commonly fall at 100 to 125 Btu/hr·ft². (5.3.2)

Hydronic design surface outputrange

Btu/hr·ft²

80250

Default: 125 Btu/hr·ft²

NOTE For electric systems, pavement watt density typically ranges from 30 to 50 W/ft²; 40 W/ft² (≈136 Btu/hr·ft²) is the common commercial pavement value in Zones 4 to 6. (5.3.3)

Electric design watt densityrange

W/ft²

3050

Default: 40 W/ft²

5.3.4Electric watt density shall not exceed 1,300 W/m² (≈121 W/ft²) per NEC 426.20; typical design values are well below this ceiling.

6 System Type

NOTE Hydronic and electric systems trade differently across plant availability, operating cost, installation complexity, and scale; the choice shall be made with the mechanical and electrical engineers of record before the system is sized. (6.1)

NOTE Hydronic systems suit larger areas and projects with an available heat source, and spread the energy demand across a fuel-fired or central plant; electric systems suit smaller areas, retrofits, and projects without a hydronic plant, at the cost of high continuous electrical demand. (6.2)

Snow melt technology typeradio

● Hydronic — glycol loop in embedded tubing

○ Electric — resistance heating cable

○ Electric — factory-assembled heating mat

NOTE Heat Source (Hydronic) (6.3)

NOTE Where a hydronic system connects to the main building hydronic system, a heat exchanger shall isolate the glycol snow melt loop from the building water side so glycol cannot migrate into potable or building heating water. (6.3.1)

Hydronic heat sourceradio

○ Dedicated boiler or water heater for snow melt

● Heat exchanger off the main building hydronic system

○ Standalone electric boiler package

7 Hydronic Components

NOTE Tubing (7.1)

NOTE Embedded hydronic tubing shall be PEX-a, PEX-b, or PE-RT rated for the design supply temperature and working pressure, supplied in continuous lengths without buried joints within a circuit. (7.1.1)

7.1.2No mechanical joint, coupling, or fitting shall be embedded in the slab within a snow melt circuit; circuits shall run continuous from supply manifold to return manifold.

Hydronic tubing materialradio

● PEX-a (ASTM F876/F877)

○ PEX-b (ASTM F876/F877)

○ PE-RT (ASTM F2623)

Tubing nominal diameterradio

○ 1/2 in

● 5/8 in

NOTE Tubing Spacing (7.2)

NOTE On-center tubing spacing shall be selected for the surface priority: 6 in OC for critical surfaces, 9 in OC for standard commercial surfaces, and 12 in OC for low-priority or residential surfaces. (7.2.1)

Tubing on-center spacingradio

○ 6 in OC (critical / hospital / ramp)

● 9 in OC (standard commercial)

○ 12 in OC (residential / low priority)

NOTE Circuit Length (7.3)

NOTE Hydronic circuit length shall be limited so that circuit pressure drop stays below 4 ft H₂O per 100 ft, which generally caps a 1/2 in circuit near 300 ft and a 5/8 in circuit near 400 to 500 ft. (7.3.1)

7.3.2Circuits served from a common manifold shall be reverse-return or balanced with manifold balancing valves so that flow is distributed evenly across loops of unequal length.

Maximum circuit lengthrange

ft

200500

Default: 300 ft

NOTE Supply Temperature and Delta-T (7.4)

NOTE The hydronic loop shall be designed for a supply temperature of 120°F to 140°F with a circuit temperature drop of 20°F to 30°F; a 130°F supply with a 110°F return is the typical commercial default. (7.4.1)

Design supply temperaturerange

°F

120140

Default: 130 °F

Design circuit delta-Trange

°F

2030

Default: 20 °F

NOTE Heat-Transfer Fluid (7.5)

NOTE Propylene glycol shall be used where system runoff can contact food-preparation areas, landscaping, or stormwater that drains to sensitive receiving waters; ethylene glycol is more efficient but toxic and shall be used only where project conditions specifically justify it and runoff exposure is controlled. (7.5.1)

NOTE The glycol concentration shall be selected for the design freeze point: 30% propylene glycol provides protection to about −15°F and is the typical North American default, while 40% is required for design conditions at or below −20°F. (7.5.2)

Heat-transfer fluid typeradio

● Propylene glycol (lower toxicity)

○ Ethylene glycol (higher performance, toxic)

Glycol concentration (by volume)range

%

2550

Default: 30 %

NOTE Make-Up, Air Separation, and Expansion (7.6)

NOTE The hydronic loop shall include a glycol make-up/fill provision, an air separator, and an expansion tank sized for the system fluid volume; snow melt loops hold large fluid volumes and omitting these provisions causes air-binding and startup failures. (7.6.1)

7.6.2A means of purging air from each circuit, such as manifold purge and isolation valves, shall be provided so that each loop can be individually filled and bled.

NOTE Manifold (7.7)

NOTE The circuit manifold shall include balancing valves, flow indication, and purge/isolation valves for each loop, and shall be located in a heated interior space or an accessible vault at the slab edge. (7.7.1)

NOTE Where the manifold is in an unheated exterior vault, the supply and return piping between the building and the manifold shall be routed through conditioned space or heat-traced so the glycol cannot freeze in the connecting piping. (7.7.2)

Manifold locationradio

● Heated interior space

○ Accessible exterior vault at slab edge

8 Electric Components

NOTE Heating Element Form Factor (8.1)

NOTE Single-conductor heating cable is field-cut to length and laid at a calculated spacing; twin-conductor cable and factory-assembled mats carry a fixed watt density and are installed by cut-and-turn at the rated spacing. (8.1.1)

Electric heating element form factorradio

○ Single-conductor heating cable (field-cut)

● Twin-conductor constant-wattage cable (field-spaced)

○ Factory-assembled heating mat (fixed spacing)

NOTE Cable Spacing and Cover (8.2)

8.2.1Adjacent cable runs shall be spaced not less than 25 mm (≈1 in) apart per NEC 426.20(B).

NOTE Minimum cover over embedded electric heating cable shall be 1.5 in of concrete or 3 in of asphalt, measured from the top of the cable to the finished surface. (8.2.2)

Minimum cover over heating cableradio

● 1.5 in concrete

○ 3 in asphalt

NOTE Branch Circuits and Overcurrent (8.3)

8.3.1Snow melt loads shall be classified as continuous loads; branch-circuit conductors and the overcurrent protective device shall be rated at not less than 125% of the connected load per NEC 210.20.

NOTE The connected electrical demand of the snow melt system shall be confirmed against the available service and panel capacity before the system is sized, because a large heated area at 40 W/ft² can draw several hundred amperes. (8.3.2)

NOTE Ground-Fault Protection (8.4)

8.4.1Each fixed outdoor electric snow melt circuit shall be protected by ground-fault protection of equipment (GFPE) set at 30 mA per NEC 426.28.

NOTE GFPE at 30 mA is equipment protection against heating-element faults in the pavement, not the 5 mA personnel-protection threshold of a GFCI; on large systems, GFPE panels selected to resist nuisance tripping should be specified. (8.4.2)

9 Controls

NOTE The control strategy shall be selected for the surface priority: fully automatic control with a pavement temperature/moisture sensor and an aerial ambient sensor is appropriate for critical and standard commercial surfaces, while semi-automatic or manual-only control may be acceptable on low-priority surfaces. (9.1)

Control strategyradio

● Fully automatic (pavement + aerial sensor)

○ Semi-automatic (manual enable, auto shutoff)

○ Manual only

NOTE Sensing (9.2)

9.2.1An automatic system shall include a pavement-mounted sensor that measures surface temperature and detects moisture, and an aerial sensor that detects ambient precipitation, so the system runs only when snow or ice is actually present.

NOTE Sensors shall be located in a representative heated zone away from artificial heat sources, drainage paths, and snow-storage piles so the reading reflects true pavement conditions. (9.2.2)

NOTE Activation Setpoint (9.3)

NOTE The system shall activate when the pavement surface temperature is at or below 38°F with precipitation detected; the activation setpoint shall be field-adjustable at the control panel. (9.3.1)

Pavement activation setpointrange

°F

3442

Default: 38 °F

NOTE Post-Precipitation Soak (9.4)

NOTE The control sequence shall continue heating for a soak period after precipitation stops so that residual melt water evaporates instead of re-freezing; a system that shuts off immediately leaves wet pavement that ices over. (9.4.1)

NOTE The post-precipitation soak time shall be field-adjustable; 30 minutes is the typical starting point for walkways and 60 minutes for ramps. (9.4.2)

Post-precipitation soak — walkwaysrange

min

1560

Default: 30 min

Post-precipitation soak — rampsrange

min

3090

Default: 60 min

NOTE Idling and Freeze Protection (Hydronic) (9.5)

NOTE The control sequence shall distinguish a snow-melt mode from a freeze-protection (idling) mode and shall define the setpoints and outdoor-reset strategy for each, so the glycol loop does not freeze when the system is off in deep cold. (9.5.1)

9.5.2A freeze-protection mode shall maintain a minimum slab or fluid temperature during extreme cold even when no precipitation is detected, where the design relies on idling to avoid a cold-start of a large fluid volume.

Operating modes providedcheckbox

☑ Automatic snow-melt on precipitation

☐ Idling / freeze-protection mode

☑ Manual override (timed run)

10 Slab Insulation

NOTE Under-slab and perimeter insulation is the single most common value-engineering deletion in snow melt design; without it, heat is lost downward, the surface cannot reach design output, and operating cost rises sharply. (10.1)

10.2Slab edge (perimeter) insulation shall be provided at not less than R-10 (≈2 in extruded polystyrene), extending down the slab edge to a depth of at least 24 in.

NOTE Under-slab insulation shall be provided at not less than R-5 where the heated slab is on grade. (10.3)

Slab edge insulationrange

R-value

1020

Default: 10 R-value

Under-slab insulation (on grade)range

R-value

515

Default: 5 R-value

11 Slab Coordination

NOTE Concrete Cover (11.1)

NOTE Hydronic tubing shall have at least 2 in of concrete cover over the top of the tube; less than 2 in of cover at tubing locations risks cracking under load. (11.1.1)

11.1.2The minimum cover over embedded elements shall be coordinated with the concrete contractor before placement so that reinforcement, tubing/cable, and finished grade are all reconciled.

NOTE Expansion and Joints (11.2)

NOTE Provisions shall be made for thermal movement of the tubing where it crosses slab expansion joints, such as a protective sleeve so the tube is not sheared or abraded at the joint. (11.2.1)

11.2.2Tubing and cable shall not pass through a saw-cut control joint; loops shall be laid out so that planned saw cuts fall between runs.

NOTE Penetrations and Transitions (11.3)

11.3.1Where snow melt tubing or conduit penetrates a fire-rated assembly at a building transition, the penetration shall be firestopped with a system tested to ASTM E814 for the rated assembly.

NOTE Locations, routing, extents, and arrangement of the heated areas, manifolds, and sensors shall be as shown on the drawings. snow melt plan (11.3.2)

12 Testing

NOTE Hydronic Pressure Test (12.1)

NOTE The embedded hydronic tubing shall be hydrostatically tested before concrete placement; once the tubing is encased there is no repair option, so the pre-pour test is a mandatory hold point. (12.1.1)

12.1.2The hydrostatic test shall be held at 1.5× the design working pressure, not less than 100 psig, for 30 minutes with no pressure drop, and the tubing shall remain pressurized through the concrete placement so that a tube damaged during the pour is revealed immediately.

Hydrostatic test pressurerange

psig

100150

Default: 100 psig

Hydrostatic hold timerange

min

3060

Default: 30 min

NOTE Electric Insulation-Resistance Test (12.2)

NOTE Each electric heating circuit shall be insulation-resistance (megohmmeter) tested at 500 V DC before, during, and after concrete placement, with a minimum acceptable reading of 1 MΩ or the manufacturer's stated minimum, whichever is greater. (12.2.1)

12.2.2Test readings shall be recorded at each stage so that damage occurring during the pour can be isolated to the placement step.

Insulation-resistance test voltageradio

● 500 V DC (standard; most pavement heating cable)

○ 1000 V DC (manufacturer-stated minimum where higher rating required)

Minimum insulation resistancerange

MΩ

1100

Default: 1 MΩ

NOTE Functional Test (12.3)

12.3.1After concrete has cured, the complete system shall be functionally tested to confirm that the control sequence activates the heating elements on a simulated precipitation/cold signal, that all circuits energize or circulate, and that the post-precipitation soak and override functions operate as specified.

13 Installation

NOTE General (13.1)

13.1.1The system shall be installed in accordance with the manufacturer's written installation instructions, the approved shop drawings, NEC Article 426 for electric work, and ASHRAE Handbook — HVAC Applications Chapter 51 for design intent.

13.1.2Embedded elements shall be secured to the reinforcement or carrier mesh at the spacing shown so they do not float or displace during concrete placement.

NOTE Protection During Placement (13.2)

NOTE The Contractor shall protect embedded tubing and cable from damage during reinforcement placement, traffic, and concrete vibration, and shall not allow vibrators or tools to contact the elements directly. (13.2.1)

13.2.2Embedded elements damaged before or during placement shall be repaired only by methods permitted by the manufacturer, or the affected circuit shall be replaced; a damaged circuit shall not be encased.

NOTE Asphalt Substrates (13.3)

NOTE Where electric elements are installed in asphalt, the elements and the placement temperature shall comply with the manufacturer's asphalt listing so that paving heat does not damage the cable insulation. (13.3.1)

14 Delivery, Storage, and Handling

NOTE Tubing, cable, and mats shall be delivered in the manufacturer's original packaging and stored protected from sunlight, physical damage, and contamination until installation. (14.1)

NOTE Heating cable and mats shall be inspected and insulation-resistance tested on receipt and again immediately before installation, and any element failing the test shall be rejected. (14.2)

NOTE Glycol heat-transfer fluid shall be stored in sealed containers and protected from freezing and contamination before charging the loop. (14.3)

15 Warranty

NOTE The manufacturer's standard warranty shall be provided for the embedded tubing or heating cable, the controls, and the heat-transfer fluid. (15.1)

NOTE The installer shall warrant the installation, including embedded-element integrity and system operation, for not less than the project's standard warranty period from the date of substantial completion. (15.2)

Installer workmanship warranty periodrange

years

15

Default: 1 years

16 Spare Parts

NOTE Spare control components — pavement and aerial sensors and any consumable control modules — should be provided so a sensor failure does not disable the system during a storm event. (16.1)

Spare parts furnishedcheckbox

☑ Spare pavement sensor

☑ Spare aerial (ambient) sensor

☐ Glycol make-up supply (hydronic)

☐ Spare GFPE module (electric)

Snow Melt Systems