Show Menu

Underfloor Heating Information

H2O Heating are the experts in all forms of under floor heating systems, whether your requirement is for a single room; extension or renovations; large scale multi-zoned development – car showroom, nursing home or a multi-million architectural residential dream you can be confident that H2O Heating will design a bespoke system that takes into consideration the occupants needs and requirements offering all our clients the same unsurpassed service.

H2O Heating use only the best products in all its systems but this is particularly important when considering an under floor heating system; only the best products from leading European manufacturers that have been well tested and developed backed by considerable warranties are incorporated into our under floor heating systems meaning you can relax safe in the knowledge your system has been designed and will be installed to the highest standard. All pipe work used by H2O Heating is supplied from leading and reputable manufacturers – either Rehau or Uponor Pe-Xa, Peroxide-Cross Linked Polyethylene Pipe – so we can be confident in the system we are supplying and installing for our clients.

The concept of underfloor heating is not new, first used by the Romans; a warm, gentle and sumptuous radiated heat is emitted from the floor warming the room. Under floor heating is ideal for homes where wall space is at a premium – such as large open plan living and rooms with high ceilings as the heat is distributed from the base.
Floor coil systems work best in rooms with a concrete or tiled finish floor but can be used with engineered timber or carpet – please consult your flooring specialist for further information.


An in-slab system is where the pipe work is fixed to a layer of the reinforcing mesh in the concrete slab floor.
A concrete cover of 50mm (manufacturer recommendation) is then poured over the pipe; when operational the hydronic boiler will supply water at 45 -50°C through the pipework there may be a variant in temperature across the floor due to the water flow temperatures (this does not affect the room’s air temperature). Please note that the engineers responsible for the floor design must be aware that 16mm pipes at 200mm centres will be laid in the floor.
*Careful consideration should be given to final floor covering, Timber and carpet are not to exceed and R Value of 0.15 M2/K/W.

Floor Coils: Secondary Pour

A secondary pour system is where the pipes are located in a second stage concrete or screed pour usually on top of the constructional slab. Most often installed using an insulted pipe positioning board.

Pipe positioning boards are a polystyrene based Insulation sheet approx 37mm thick with an R value up to 1.0; the advantage of using pipe positioning boards is that they create a thermal break between the constructional slab and the topping slab/screed, this thermal break increases the efficiency of the system by reducing the heat up time as you are only heating up the secondary layer of concrete/screed which tends to be a reduced thickness.

This system is not recommended for a polished screed finish due to the possibility of cracking in the finished floor – please speak to one of our knowledgeable sales staff for further information.

Floor Coils: Diffusion Tray

A diffusion tray system allows underfloor heating to be installed in to a suspended timber floor where normally an underfloor heating system would not be possible. A diffusion tray adds as a spreader plate to distribute the heat laterally underneath the timber sub floor.

Diffusion trays are installed between the floor joists and are approximately 380mm wide so careful planning during engineering is required – for further information at design stage please consult with one of our experts.


Pipe work will be installed in a per-determined pattern to give optimum performance suitable for each individual room. Each circuit is a maximum length of 100m and larger rooms may have multiple circuits. There may be a variant in temperature across the floor due to the water flow temperatures, (this does not affect the room’s air temperature).

A distribution header will be installed above floor level, inside or outside the building, generally in a central location; the distribution header can be housed in cabinetry as long as it is accessible. Each floor coil circuit can be controlled by an on/off valve fitted to the header which allows for the control of which rooms are to be heated. Further Individual Zone control of each room is available, but must be included at the design stage.

Benefits of Under Floor Hydronic Heating Systems


A floor coil system is the cheapest form of hydronic heating to run; the running costs are lower due to the hydronic boiler operating at a lower supply temperature – thus resulting in less gas consumption.


Floor coils systems, like other types of hydronic heating systems, offer increased efficiency through the ability to zone the system using an electronic actuation control system, thus offering a room by room controlled environment in your home.

Floor coils are particularly effective when coupled with a high efficiency condensing boiler due to the low return water temperatures. Under floor heating systems account for over 60% of the European market due to their high efficiency; running costs are lower due to the heating boiler operating at a lower supply temperature.


Due to the very nature of an underfloor heating system heat is emitted from the lowest part of the room- the floor – and distributed evenly thus eliminating cold spots and further adding to your comfort.


A floor coil system can be mix and matched with standard and/or designer radiators using a special partage system adding to the flexibility of the system and making the design possibilities endless.

Underfloor Heating pipe

At H2O Heating we use two types of under floor heating pipe; Uponor Comfort Pipe PLUS and Rautherm-S Floor heating pipe from Rehau. Both of the pipe systems are German engineered from long standing reputable companies and both offer exceptional warranties of 10 years for installed pipe.

Uponor is an international market leader in Plumbing and indoor climate systems, “designed for efficient performance, long lifetime, easy installation and a low environmental footprint” Taken from Uponor With origins from 1918 Uponor first started manufacturing plastic pipe in 1965 today they continue manufacturing adhering, and often exceeding, to the strict principles set under ISO 9001 ensuring their pipe is manufactured to a high quality.

Uponor Comfort Pipe PLUS

PE-Xa pipe with an oxygen diffusion layer of EVOH (ethylene vinyl alcohol), with an extra outer protection layer in white colour with two blue stripes. Complying with EN ISO 15875 “Plastic piping systems for hot and cold water installation – Cross-linked polyethylene” and fulfils the requirement for oxygen diffusion resistance as per DIN 4726.

Application class 4+5/ 6 bar
Max design temperature: 90°C
Malfunction temperature: 100°C
Design pressure 6/8 bar at 90°C/70°C
Fire class: E according DIN EN 13501-1

Rehau is a global leader in the manufacturer of polymer based products with over 50 years experience in the plumbing and heating industry. REHAU has developed a comprehensive hydronic heating solution that systematically addresses the needs of designers, installers, builders and homeowners alike taken from Rehau With a reputation worldwide for research and development and the production of innovative solutions with quality products.

Rautherm-S Floor heating pipe (PE-Xa cross-linked polyethylene pipe)

Million metres of RAUTHERM S pipe have proven its quality during installations across the globe in the last 30 years. – Completed by the permanent leak-proof compression sleeve jointing technology, REHAU RAUTHERM S piping system with EVOH oxygen barrier provides a no-worry installation, each and every time.

The Rehau S-floor heating pipe is made from RAU-PE-Xa – Peroxide-crosslinked polyethylene (PE-Xa). – with a PE-Xa inner layer and an outer EVOH oxygen barrier with red adhesive for clear distinction as radiant heating/cooling pipe.

Oxygen-tight according to DIN 4726.

Suitable for use in heating and cooling applications in residential and commercial applications in accordance with BS EN 1264 and BS 7291.