SPC Flooring, Underfloor Heating and Sunlight: The 27°C Limit

Kermit SPC flooring can be used with underfloor heating when the selected flooring and heating assembly are compatible, and the finished floor surface stays at or below 27°C at every point. The limit applies to the floor surface. It is not a heating-water temperature or a room-thermostat setting.

A suitable installation needs three decisions: the flooring and underlay assembly, the system that controls the surface temperature, and the way sunlight or furniture may create local hot spots. Agree all three before the floor is ordered.

Use this guide with Kermit's English underfloor heating PDF and the complete English installation manual. The heating supplement does not replace the instructions for the selected product and locking system.

Keep three temperature readings separate

Reading	What it tells you
Room temperature	The air temperature at the room sensor; it does not establish the hottest floor-surface temperature
Heating-water temperature	A system operating value to be set by the heating specialist; it is not the permitted floor-surface temperature
Finished floor-surface temperature	The temperature of the installed flooring, which must not exceed 27°C

Kermit's heating guide calls for a thermostat with a floor sensor. Ask the heating installer to confirm the control arrangement and how surface-temperature limits will be maintained throughout the occupied area. A reading from one location may not reveal a sunlit patch or heat trapped elsewhere.

Do not turn the system up simply because the air in the room feels cool. First check the controls, floor-surface readings and the building's heating requirements. The flooring temperature limit remains the same when the room needs more heat.

Agree the complete flooring and heating assembly

Confirm the collection, decor, thickness, backing and heating-system type. The installation manual allows compatible water-based systems within its stated conditions. It restricts electric and infrared applications and requires avoiding direct contact with heating elements. An electric mat or film should therefore not be treated as approved just because SPC appears in its advertising.

For an electric or unusual retrofit system, obtain agreement on the exact build-up and temperature controls from Kermit and the heating-system supplier before proceeding. Product-specific preparation and embedding conditions must be checked in the complete manual. A temperature limit alone is not a full installation specification.

Attached backing also varies. Some Kermit collection profiles list integrated IXPE, while the documented 6 mm configuration has no attached IXPE. Use the specification guide to keep those configurations separate. Add an extra underlay only when it is approved for both the chosen flooring and the heating assembly.

Ask for thermal-resistance information for the whole relevant floor-and-underlay assembly. A result for one plank cannot establish the behaviour of an additional insulating layer. This guide does not promise a fixed heat output or energy saving; those depend on the building and heating design as well as the floor.

Complete drying and start-up in the right order

The MMFA heating guidance also calls for coordination of the heating system, screed and floor covering, with a drying and heating-up record. For Kermit, use the following sequence with the applicable product instructions:

1. Identify the screed and complete its drying and heating-system commissioning requirements. Record the moisture test method and the acceptance limit that applies to that screed.
2. Switch the heating off for flooring installation and allow the floor to reach the required fitting conditions. Follow the installation manual for acclimatisation and the selected joining method.
3. Confirm the movement-gap and transition plan before covering the perimeter. Kermit's minimum clearance is 10 mm at walls and fixed objects.
4. At initial start-up, increase the temperature gradually by 3–5°C per day, as stated in the heating guide, while checking the finished floor surface. Stop at the desired comfort level and keep every part of the surface at or below 27°C.

The daily increase is not an instruction to keep raising the temperature after the comfort level or surface limit has been reached. Agree the commissioning schedule and controls with the installer, and record the actual settings at handover.

Treat sunlight as a separate heat source

Large windows can expose one part of a room to much stronger sunlight than another. Closing the underfloor-heating valve does not control solar heat arriving through the glass. Plan blinds, curtains or suitable shading and check the exposed floor under the conditions in which the room will be used.

Kermit's guidance does not approve uncontrolled conservatories, unheated holiday homes or other extreme conditions. Review the actual room use and exposure before specifying the floor. Indoor-use wording should not be read as approval for every enclosed space.

Heat and colour change are also different issues. The care manual advises controlling strong sunlight to reduce long-term colour change. A surface treatment or a laboratory result should not be read as a promise that prolonged exposure can never affect appearance.

Check rugs, furniture and local heaters

Rugs, low-clearance furniture and local heat sources can change conditions at a small area of the floor. Follow the heating guide's instruction to prevent trapped heat and local overheating. Discuss the intended furniture and rug arrangement with the heating installer, rather than checking only the empty room.

Keep portable heaters and hot objects from creating concentrated heat at the surface. Do not let skirting, fixed cabinets or profiles restrain the floating floor. Heating suitability also does not change Kermit's limits on bathroom floors, outdoor use or areas cleaned by hosing.

Hand over settings as well as a finished floor

Keep the selected flooring and underlay details, system identity, screed drying record, moisture acceptance, sensor/control arrangement and start-up record together. Show the occupant where to check the settings and explain that changing rugs or furniture can alter local conditions.

For the rest of the site checks, use the installation planning guide. The person responsible for the floor should receive the manuals and agreed limits at handover, not have to reconstruct them after a heating problem.

Heating and sunlight questions

Does 27°C refer to the heating water?

No. It is the maximum temperature of the finished flooring surface. A heating specialist must set the system so that the floor stays within that limit; room and water readings are different measurements.

Can I add another underlay for more comfort?

Only if it is approved for the selected flooring and heating assembly. Confirm any attached backing first. Additional layers can affect both support and heat transfer, so thickness alone is not a basis for choosing them.

Does a room thermostat protect a sunlit floor from overheating?

It does not establish the temperature of every part of the floor. Direct sunlight and trapped heat can create local hot spots. Use the specified floor-sensor controls, manage exposure and have the installer check the relevant locations.

Does suitability for heating also approve floor cooling?

No. Cooling needs a separate compatibility assessment and dew-point controls to prevent condensation. Check the complete Kermit manual and the heating/cooling system instructions before including cooling in the project.