A cold room may need underfloor heating, particularly when a freezer is built over the ground. The decision depends on the operating temperature, floor construction and conditions beneath it. For a ground-supported freezer, frost-heave protection should be addressed during design. Electric heating is one possible solution.
The purpose of this heating is to protect the ground or building structure. It is different from comfort heating, and it should not be specified simply by asking how warm the floor should feel. For projects in Singapore, start with a floor section and a clear description of the room’s intended use.
Understand the risk beneath a freezer
A freezer continuously draws heat from its surroundings. Over time, the ground below it can become cold enough for moisture to freeze. In susceptible soil with a water supply, water can migrate towards the freezing zone and enlarge ice lenses. This ice growth can lift and damage the floor, a process called frost heave. Insulation slows heat transfer but does not generate replacement heat. A thick insulation layer alone is therefore not proof that the ground is protected. (See RAYCHEM’s freezer frost-heave design guide; Engineering New Zealand’s coldstore practice note.)
Singapore’s warm climate does not remove the need for this assessment: the low-temperature room operates regardless of outdoor weather. Ask how the proposed construction keeps the ground from freezing throughout the intended operating conditions.
Check which floor arrangement applies
A freezer on a ground-supported slab
Identify what sits beneath the insulation, including the slab, fill and soil. The design should establish how frost-heave protection will be provided and maintained. ASHRAE describes electric cables, heated air and circulating glycol as possible methods. It also notes that suitably designed ambient-air ventilation beneath the floor may be sufficient in warmer climates. (See ASHRAE refrigerated-facility design guidance.)
A room operated above freezing
A room consistently operated above freezing generally does not need the same ground frost-heave protection. Its insulation, moisture control and floor loading still need review. Tell the designer if future freezer use is possible; a floor selected for chilled storage should not be assumed suitable for lower temperatures. (See ASHRAE guidance on floor construction and future use.)
A cold room on a suspended floor
For a floor spanning a space below, assess the actual structure and surrounding air. Condensation can form if an exposed surface falls below the adjacent air’s dew point. The response may involve insulation continuity, vapour sealing, humidity control or purpose-designed heating. Devex describes heating beneath suspended slabs as one condensation-control application. It requires a different assessment from soil frost heave. (See Devex’s refrigeration heating guidance; ASHRAE envelope design guidance.)
Specify what the heating is protecting
For ground frost-heave protection, the heating is normally arranged beneath the floor insulation to protect the subfloor or ground. The refrigerated wearing surface remains on the cold side. The drawings should show the actual layer sequence, heater location and sensor positions so that the civil, insulation and electrical works can be coordinated. (See RAYCHEM’s installation manual.)
Keep other heating duties separate in the specification. Door thresholds, door frames and drainage may need their own protection. A threshold heater does not demonstrate that the soil beneath the whole room is protected. DEVI identifies several distinct cold-store heating applications. (See DEVI’s cold-store frost-protection guidance.)
Compare complete protection systems
Ask the designer to explain why the proposed method suits the project. Electric heating needs an appropriate power supply and controls. A circulating-fluid system needs a dependable heat source and circulation. An air-based arrangement depends on the designed airflow path remaining effective.
Compare access for repairs, operating cost and the response to a failure as well as the installation price. If ventilation or another alternative is proposed, request its design basis. An unverified void or an opening beside the room is not enough information to establish that the ground will remain protected.
Heating output, spacing and control settings must follow the project calculation and selected system. Room size alone is insufficient. RAYCHEM’s design guide, for example, considers floor insulation and the lowest intended operating temperature. Avoid copying a generic watts-per-square-metre value from another installation. (See RAYCHEM’s design requirements.)
Include testing and fault response
Specify how the owner will know the protection is working. Agree which temperatures and equipment faults will be monitored, who receives alarms and what they should do. Ask whether standby capacity or replaceable components are appropriate for the installation, particularly where heating elements will be inaccessible.
Commissioning should follow the selected manufacturer’s instructions, with electrical testing performed by qualified personnel. For an electric system, the handover may include cable test results, sensor and controller checks, protection tests and operating records. RAYCHEM’s manual provides commissioning and maintenance procedures for its systems. The project team should also demonstrate the specified alarm response and leave clear operating instructions. (See RAYCHEM’s commissioning and maintenance guidance.)
The room’s normal air-temperature display does not verify the condition beneath the floor. Keep underfloor protection in the maintenance plan and investigate its alarms even when stored products remain cold. Do not disable protection or change its settings simply because the room remains cold; agree any shutdown with the responsible designer.
Prepare the information before requesting a quotation
Present and possible future operating temperatures
Room dimensions and a section through every floor layer
Whether the floor is ground-supported or suspended, and what lies beneath it
Available insulation specifications, soil and moisture information, and adjacent-space temperature and relative humidity
Available power, heat sources and access for maintenance
Required monitoring, alarms and arrangements for a protection-system failure
For an existing installation, provide drawings and service records if available. New cracking, uneven floors or persistent condensation call for investigation; they do not establish frost heave by themselves. Arrange an engineering assessment before changing the heating or lowering the room temperature.
Planning a cold room or converting a chiller to freezer duty? Contact Airnovation with the layout, floor details and intended temperatures to discuss a suitable floor-protection approach.
Related reading: Chiller vs Freezer Cold Room: Which Does Your Business Need?