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Underfloor Heating

The perfect partner for an Air Source Heat Pump is Underfloor Heating. This is because Air Source Heat Pumps are more efficient the lower the water temperature and as Underfloor Heating operates at lower temperatures than radiators, it is clear why it is a perfect match.

Underfloor Heating has a more even distribution of heat since there is pipe in the floor evenly spaced that emits a nice gentle warmth that gives a warm floor which gets cooler at ceiling height. Underfloor Heating is typically more efficient than radiators as it operates on lower temperatures and it also frees up valuable wall space.

There are a number of installation options available and at Unitherm, we have the solutions to meet with the building.

Please find detailed below the floor construction details and core components for Unitherm’s range of warm water underfloor heating systems:

Floor Construction Details


The Uni-staple system provides a quick, flexible and simple method of securing the underfloor heating pipework when laying a screed floor. The staples have a barbed end which fixes into the insulation. To speed up the process further, a pipe stapler is available. In preparation for certain screeds, a polythene sheet/membrane may be required over the insulation prior to stapling the pipe.


The Uni-Cliprail system provides a quick, flexible and simple method of securing the underfloor heating pipework when laying a screed floor. The cliprail has an adhesive back which fixes onto the insulation. In preparation for certain screeds, a polythene sheet/membrane may be required over the insulation prior to stapling the pipe.

Uni-Spider25 / Uni-Spider Slim20

The Uni-Spider25 / Uni-Spider Slim20 system comprises of a series of interlocking castellated panels which have been designed to avoid using cliprail and staples to speed up the installation of the underfloor heating system. It has an adhesive layer on the underside to ensure no movement when the screed is poured. This design enables very thin screeds to be poured over the panel to give the lowest possible build.


The Uni-Foilboard20 is a low profile, light weight system, ideal for all types of installation especially where the floor height is a premium. The insulation panel is pre-grooved, a foil reflective layer is then heat-adhered to produce an effective high output panel. When using carpet or a thin laminate, a 6mm flooring grade plywood would need to be used.


The Uni-Gyspum18 is a low profile high performance system manufactured from reinforced gypsum, the CNC routed panels with universal bulb returns are engineered to provide an optimum heating system. There are significant installation time saving benefits over that of a wet system. A flexible adhesive should be used when installing tiles.


The Uni-Foilchip22 is a structural heating board which gives rapid even heat distribution, dry construction and is fully recyclable. With a 22mm thickness, a 6mm flooring grade ply would need to be bonded and mechanically fixed to the chipboard prior to any floor covering. This can be installed on solid, joisted and battened floors.


The Uni-Joistplate is a double channel aluminium diffuser plate which sits between joists. When notching joists, this needs to be done in accordance with the relevant building regulations. Web/Eco joists & I-beams can be utilised without the need to notch the joists. This design is ideally suited for new build applications.


The Uni-Pugscreed can be used with either just staples or you can install cliprail for extra security of the pipe. The screed density can vary depending on the thickness of screed installed. When installing intoa joisted floor system, the joists must be correctly sized to accept the additional loading. Battens can be installed onto a solid floor to reduce the screed thickness.

PEX-b 16mm; PE-RT 12mm

Our multi- layer underfloor heating pipe comes with a 50 year warranty and conforms to ISO 9001 & DIN 4726. Both our 16mm & 12mm are available in various coil lengths. We would recommend the user of a De-Coiler when using the larger coils.

Uni-Mix LV

The Uni-Mix LV is designed to blend flow and return from your heat source to provide a constant floor temperature throughout. With an operating range of 30-65° and featuring a fully ERP compliant, energy efficient circulator as well as a port for an automatic air vent. Also, it comes with a compact bolt on the unit which provides a quick and simple installation.

Dynamic Balancing SS Manifold

Stainless steel manifold for UFH systems with dynamic flow balancing and independent setting for each individual circuit, consisting of:

  • Delivery manifold with flow meters with fluid shut-off function
  • Return manifold with dynamic flow balancing valves and manual handwheel (M30 x 1,5 mm connection), prearranged for thermo- electric command via R473/R473M actuators that can be installed after fitting the relative R453FY002 ring nut (to be ordered separately)
  • Pair of end pieces with self-sealing complete with drain cocks, manual air vent valves and specific R74 key
  • R588Z metal brackets
  • R73PY010 key for presetting

Floor Coverings

Please see detailed below, details on typical floor coverings when used in conjunction with a Unitherm underfloor heating system:

Carpet – The combined tog value of the carpet and underlay should NOT exceed 2.5 tog, but its preferential for the combined tog value to be below 2.

Solid Wood – Solid hardwood should be kiln dried with a minimum moisture content of between 6% - 9%. The hardwood should also be stored in a dry place, acclimatised prior to laying and a floor sensor fitted to avoid overheating.

Laminate – A more stable floor covering than solid wood and its more hard wearing. Laminate can be easily installed on underfloor heating as a floating floor or with an adhesive, but check with the supplier for installation instructions. The floor temperature should not exceed 27°C, so a floor sensor should be fitted to avoid overheating.

Vinyl – Whilst vinyl works well with underfloor heating, it should be noted that the floor temperature should not exceed 26°C and therefore a floor sensor should be fitted. Also, vinyl should be acclimatised prior to installation by unwrapping and it being loose laid in the room that the vinyl is to be fitted for at least 24 hours prior to fixing.

Tiles – A very common floor covering with underfloor heating since tiles conduct heat well which means that the underfloor heating system will operate more efficiently and heat the room quicker. A decoupling membrane is recommended as this will isolate any movement and therefore protect the tiles from cracking.