Standard Carbon vs. PTC Film: How to Choose the Right Underfloor Heating Kit

If you are researching an electric infrared underfloor heating kit for a UK retrofit or new build, you have likely noticed that not all heating films are created equal. The market is crowded with standard carbon films, but the real conversation in 2026 centres on PTC self-limiting technology, power density, and long-term running costs. This guide cuts through the noise. It explains what a complete kit should include, why the wattage per square metre matters for British homes, and how to avoid the hidden pitfalls that lead to cold spots, wasted energy, or a failed installation. By the end, you will know exactly what to look for in a kit and why the technology inside the film is the single most important factor in your decision.

Table of Contents

• What Is an Electric Infrared Underfloor Heating Kit?
• Why Choose a PTC Carbon Film Kit Over Standard Options?
• Power Ratings, Thickness, and Coverage: Choosing the Right Kit
• Installation: Can You Fit an Infrared Kit Yourself?
• Running Costs: How Much Does It Cost to Heat a Room?
• Compatibility: Which Floor Types Work Best?
• Warranty and Longevity: What to Expect from Your Investment
• Frequently Asked Questions
• Conclusion: Is an iHelios Electric Infrared Kit Right for You?

What Is an Electric Infrared Underfloor Heating Kit?

An electric infrared underfloor heating kit is a pre-packaged system designed to warm a room using far-infrared radiation rather than convection. Unlike traditional water-based underfloor heating or electric cable mats that heat the air, infrared film transfers warmth directly to the floor surface, furniture, and people. The effect is similar to standing in direct sunlight on a cool day: you feel the warmth even if the air temperature is modest.

A complete kit from a reputable supplier like iHelios includes every component needed for installation. You get the heating film itself, connection clips, joining tape, butyl tape for sealing electrical connections, and a vapour barrier foil. The thermostat, whether a basic digital model or a Wi-Fi-enabled smart unit, is typically included or offered as a matched accessory. The "kit" concept matters because it eliminates the guesswork of sourcing compatible parts from different suppliers. For a UK homeowner, this means no last-minute trips to a trade counter and no risk of mismatched connectors that could compromise safety or void the warranty.

The film itself is astonishingly thin, typically less than 0.5mm. This profile is a fraction of the height of a standard electric cable mat and adds virtually nothing to the finished floor level. For period properties where door clearances and skirting boards are already tight, this slimline design is often the difference between a viable retrofit and an expensive floor reconstruction.

Why Choose a PTC Carbon Film Kit Over Standard Options?

When selecting an electric infrared underfloor heating kit, the choice between standard carbon and PTC carbon film is the most critical decision for performance and safety. PTC stands for Positive Temperature Coefficient, a property that fundamentally changes how the film behaves as it warms up.

Standard carbon film operates at a fixed resistance. Apply power, and it draws a constant current until the thermostat tells it to stop. If a section of standard film is covered by a rug, a dog bed, or a piece of furniture pushed out of place, that area can trap heat and continue to rise in temperature. The result is a hot spot that, over time, can degrade the film, damage the floor covering, or in extreme cases, pose a fire risk.

PTC carbon film, by contrast, is self-limiting. As the film reaches its target temperature, its electrical resistance increases, and the power draw automatically reduces. This intrinsic safety mechanism means the film cannot overheat, even if a section is partially covered. For a British living room where furniture gets rearranged or a bedroom where a laundry basket might sit on the floor, this self-regulating behaviour is not just a technical nicety; it is a genuine safety advantage.

The longevity argument follows directly from this thermal stability. A film that never exceeds its design temperature experiences less thermal stress. The carbon particles, the copper bus bars, and the laminated layers all expand and contract less over thousands of heating cycles. In a UK climate where underfloor heating might run for six months of the year, that reduced fatigue translates into a system that performs consistently for decades rather than years.

Power Ratings, Thickness, and Coverage: Choosing the Right Kit

Understanding the wattage of your electric infrared underfloor heating kit is essential because it determines whether the system will serve as a primary heat source or a supplementary comfort layer. Power ratings across the market range from 100W/m² to 220W/m², and the right choice depends on your room's construction and insulation level.

A 100W/m² kit is suitable for well-insulated modern homes where the underfloor heating is providing background warmth rather than replacing radiators entirely. For older UK properties with solid concrete floors or rooms with high heat loss, a 140W/m² to 220W/m² output is necessary. The iHelios 220W/m² kit is engineered for exactly these demanding scenarios: suspended timber floors with draughts, conservatories with large glazed areas, and solid subfloors that act as a significant heat sink. Higher wattage means faster warm-up times and the ability to achieve comfortable floor temperatures even when outside temperatures drop below freezing.

Film thickness is a specification that deserves attention, particularly in retrofit projects. The heating film measures 0.5mm, which is thinner than a standard credit card. When combined with a 5mm or 10mm insulation board, the total build-up is still under 12mm. This minimal height increase means you can install the system without planning doors, adjusting stair noosing's, or creating awkward transitions between heated and unheated rooms. For UK homes where floor height differentials are already a common quirk, preserving the existing levels is a significant practical benefit.

Cutting intervals dictate how precisely you can fit the film to your room's layout. Most films can be cut every 25cm along marked lines, allowing you to create a heating layout that navigates around kitchen islands, toilet pans, and fitted wardrobes. You never cut across the film's width; you only cut at the designated intervals along its length. This modular approach means you can cover irregular floor plans without wasting material or leaving cold strips.

Thermostat capacity is the final piece of the sizing puzzle. A standard 16 Amp thermostat can handle a maximum load of approximately 3,680 watts.

For a 220W/m² iHelios heating film, that equates to roughly:

3,680W ÷ 220W/m² = 16.7m²

So, as a safe guide, one 16A thermostat can control approximately 16m² of 220W/m² heating film.

If your room exceeds this area, you should consider either multiple thermostats zoned independently or installing a contactor setup, which allows a single thermostat to control a larger heating load safely.

Calculating this before ordering helps avoid discovering that your kit exceeds the thermostat capacity or needs a different electrical setup.

Installation: Can You Fit an Infrared Kit Yourself?

The installation of an electric infrared underfloor heating kit splits neatly into two phases: the physical laying of the film, which is a competent DIY task, and the final electrical connection, which must be carried out by a qualified electrician. In the UK, this is not optional advice; it is a requirement under Part P of the Building Regulations for any fixed electrical installation in a domestic setting.

The process begins with subfloor preparation. For concrete subfloors, a damp-proof membrane is essential, followed by a rigid foam insulation board of at least 10mm thickness. The insulation prevents heat from being absorbed uselessly into the concrete mass below. For suspended timber floors, a 5mm or 6mm insulation board is typically sufficient, but you must ensure the boards are level and free from protruding nails or screws that could puncture the film.

Once the insulation is down, the heating film rolls out directly on top. You cut it to length at the marked intervals and position the panels to cover the walkable floor area, leaving a 10cm to 15cm gap around the perimeter and avoiding areas under fixed cabinetry. Connection clips pierce the copper bus bars at the edge of the film, and butyl tape seals each connection point against moisture ingress. The thermostat sensor sits in a channel cut into the insulation board, positioned between two heating elements so it reads the floor temperature accurately.

The floor covering goes directly on top of the film. Laminate and engineered wood flooring float over the system without adhesive, making them the most straightforward options. Once the floor is laid, a qualified electrician makes the final hardwired connection to the fused spur and tests the circuit. This two-stage approach keeps labour costs manageable while ensuring the installation is safe, compliant, and covered by the manufacturer's warranty.

A note on bathrooms: heating film is not rated for wet areas classified as Zone 1 or Zone 2 under the wiring regulations. If you want underfloor heating in a bathroom, a cable mat system designed for tiled wet floors is the appropriate alternative.

Running Costs: How Much Does It Cost to Heat a Room?

Infrared underfloor heating does not run continuously like a storage heater. Once the floor mass reaches the set temperature, the thermostat switches the system off, and the floor releases stored heat gradually. This cycling behaviour means the actual power consumption is roughly half of the film's rated output, a principle known as the 50 percent duty cycle.

Consider a 5 square metre room fitted with a 220W/m² iHelios infrared heating system. The total connected load is 1,100 watts (1.1kW). Assuming a 50% duty cycle, the average power draw over an hour is approximately 550 watts (0.55kW).

Based on a UK electricity price of £0.25 per kWh, running the system for 8 hours per day would cost around £1.10 per day.

Over a typical month of weekday use (20–22 days), this equates to approximately £22–£24 per month. For rooms with good insulation and smart thermostat control, actual consumption may be lower, as the system only uses full power during heat-up periods before cycling to maintain comfort.

These figures depend heavily on the quality of the floor insulation. A system installed directly onto an uninsulated concrete slab will lose a significant portion of its heat downwards, forcing the film to run for longer cycles and potentially doubling or tripling the running cost. The insulation board is not an optional extra; it is the foundation of an efficient system.

Smart thermostats add another layer of cost control. Wi-Fi-enabled thermostats compatible with iHelios kits allow you to set schedules that match your occupancy patterns, so the heating is not running in an empty house. Some models support geofencing, automatically lowering the temperature when your phone leaves the vicinity and warming the floor ready for your return. These features chip away at wasted energy without requiring any daily input from you.

Compatibility: Which Floor Types Work Best?

The best floor coverings for an electric infrared underfloor heating kit are laminate and engineered wood. Both materials have low thermal resistance, meaning heat transfers through them efficiently, and both are dimensionally stable under the moderate temperatures the film produces. The floating installation method used for laminate and engineered wood also makes them ideal partners, as no adhesives or nails risk damaging the film beneath.

Luxury Vinyl Tile, or LVT, is an acceptable alternative provided the manufacturer's guidelines confirm compatibility with underfloor heating. The maximum floor surface temperature should not exceed 27°C for most LVT products, which is well within the range of a properly controlled infrared system.

Carpet can work, but only with strict limitations. The combined tog rating of the carpet and any underlay must not exceed 2.5 tog. Crucially, you must not install a standard foam underlay between the heating film and the carpet. The film sits directly on the insulation board, and the carpet sits directly on the film. A thick underlay acts as a thermal barrier, trapping heat below the carpet and causing the system to run inefficiently or overheat.

Natural stone and ceramic tiles are technically compatible but require more work.

Warranty and Longevity: What to Expect from Your Investment

A quality electric infrared underfloor heating kit from a manufacturer like iHelios comes with a 20-year warranty as standard. This covers defects in materials and workmanship, giving you a decade of peace of mind. The expected lifespan of PTC carbon film, however, extends well beyond the warranty period. With no moving parts, no fluids to leak, and no combustion process, the film itself has a projected service life of 20 to 50 years when installed according to the manufacturer's instructions.

Warranty claims are rare, but when they do arise, the cause is almost always an installation error.  Following the installation guide to the letter is the simplest way to protect your investment.

Conclusion: Is Electric Infrared Kit Right for You?

An electric infrared underfloor heating kit from iHelios is designed for the UK homeowner who values safety, efficiency, and long-term reliability. The PTC self-limiting film sets it apart from standard carbon alternatives, offering inherent overheating protection and consistent performance across decades of use. The 220W/m² power density makes it suitable for the solid floors and period properties that define much of Britain's housing stock, while the ultra-thin profile preserves your existing floor heights.

If you are planning a laminate or engineered wood floor and want a heating system that is straightforward to install, economical to run, and backed by a 20-year warranty, measure your room, check your subfloor type, and explore the iHelios range for the kit that matches your space. With UK-based support and a technology that prioritises safety at every watt, it is a decision that pays back in comfort from the first cold morning you switch it on.