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)

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)

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)

NOTE Action Submittals (3.1)

NOTE Closeout Submittals (3.2)

NOTE Informational Submittals (3.3)

NOTE Installer Qualifications (4.1)

NOTE Source Quality (4.2)

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)

NOTE Pre-Pour Coordination (4.3)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

NOTE Cable Spacing and Cover (8.2)

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)

NOTE Branch Circuits and Overcurrent (8.3)

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)

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)

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)

NOTE Sensing (9.2)

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)

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)

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)

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)

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

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)

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)

NOTE Penetrations and Transitions (11.3)

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)

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)

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)

NOTE Functional Test (12.3)

NOTE General (13.1)

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)

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)

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)

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)

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)