Clay Heating Panels – Thermal Heating System


Clayworks Clay Heating Panels are clay and wood fibre dry-lining boards with integrated heating pipes designed to carry hot or cool water through walls or ceilings. The panels thereby act as the heating or cooling element within a building.

They have a sandwich construction made of wood fibre and naturally dried clay plaster. The integrated heating pipes are identical to those used in underfloor heating and require no specialist plumbing.

Once installed, the system is invisible to the eye as it sits within the walls or ceilings. The application of a thin layer of fresh clay plaster completes the installation, creating a beautiful, seamless and healthy finish.

Once linked to a heat source, the panels warm up gently to radiate heat either downwards or across the room. The individual heating loops are linked to thermostats which allow the end user to control the temperature as they would do with conventional heating systems.

Clayworks Clay Heating panels are well suited for natural heat sources such as solar and ground source heat pumps. In warmer climates, running cold water through the pipes offers a gentle and healthy alternative to mechanical air conditioning.

The panels are 62.5cm wide and 115cm long and are supplied with the heating pipes already fully integrated. Such an extremely high level of prefabrication allows for fast, cost effective installation. This saves working hours and drying times on the construction sites, leading to significant savings on time and material resources on site.



Due to the excellent breathability of both wood fibre and clay, our panels help minimise damp, aid thermal comfort and help protect the structural integrity of the building.

Infrared heat is used in medicine and is known to be gentle and effective.

Clayworks Clay Heating panels offer all of the health and sustainability benefits of clay when used as an internal building material:

• No VOCs
• No toxins
• No off-gassing
• Critically, clay helps to keep room humidity at between 40% and 70% the level at which the majority of adverse health effects are kept at bay including asthma. At these levels the likelihood for airborne infectious bacteria and virus to survive is the lowest.


The panels are perfect as a cooling system: if cold water is sent through the water pipes, the system functions as gentle air conditioning without the noise, draftiness and high maintenance associated with traditional air conditioning systems.


The panels are particularly valuable for historic building refurbishments due to their permeability. Clay plaster allows walls within buildings to breathe.  The system also offers an alternative to underfloor heating where historic floors need to be preserved and areas of walls or ceilings are more suitable for integrated heating.


Just like underfloor heating, integrated clay panel heating increases usable space as it removes the need for radiators. Especially when placed in ceilings, the system offers future design flexibility adding to the lifespan of the building.

A minimalist aesthetic is easily achieved.

Having the heating pipes integrated into dry lining boards also means that partitions can be built using the panels. This is an easy and efficient way to create partitions which not only include heating but also offer acoustic benefits. The weight of the clay is beneficial for cross-room noise reduction and the permeability of the panels buffers reverberation.

There are no design limitations due to the size of the individual boards or the pipes running through them because the heated boards are installed in combination with plain boards which can be cut to size. The only limit there is lies within the minimum size of a single heated board.

A range of specialist products is available for applications such as windows, external walls or areas of thermal bridging.


Wall heating in particular delivers targeted heat to specific areas where the effect of other heating systems can be lost due to drafts or challenging layouts. This is particularly valuable in open plan areas such as shopping centres, airports or office receptions. Heated walls behind reception desks directly benefit the wellbeing of staff and visitors whilst gentle heat in restaurants or spas behind built in seating can increase the overall level of comfort.


The way we feel warmth depends upon the total energy that reaches us – the more heat radiation, the less heat conduction is necessary. As a result, the room temperature can be reduced by 3 degrees while still giving the same feeling of warmth, enough to reduce heating costs by up to 18%.

In addition, the actual heat output of wall and ceiling heating tends to be far more effective than underfloor heating. The pipes run much closer to the surface and clay has superior heat conductivity to concrete or screed. There also is no need to wait for the heat to come through added layers such as timber flooring or tiles.


For heating internal rooms by cladding walls and ceilings, including bathrooms and toilets. Clay panels are not suitable for areas where there is contact with running water.


• Excellent sound insulation. Sound can be reduced by high mass material or soft wave reducing material.

• Basic thermal insulation: The core of the Clayworks Panel is 17mm wood fibre which provides good basic insulation.

• High inherent stability – excellent for stud constructions.

• The system regulates humidity, helping to keep a room at about 50%, optimum for helping to prevent asthma as this helps to keep the mucous membrane from drying out.

• Absorbs and stores indoor air pollution.

• The clay’s capillary structure, its permeability and the number of micro cavities enables the material to absorb and store odours and smells and Ionise the air, contributing to a feeling of fresh air.

• Energy-efficient: the panels store the warmth from the day and release it slowly in the night hours.

• Constructed primarily of ecological materials – wood and straw.

Clay works clay panels are highly sustainable due to the low energy required during production and the raw materials used. Clayworks clay boards can be 95% recycled.

• High efficiency due to warmth insulation towards the wall which insulates against heat escaping into the wall or ceiling.

• The clay plasters and panels absorb the warmth of the heating system and deliver it into the room by longwave, healthy warmth radiation.

• Fast temperature response – within 5-10 minutes – due to the low mass compared to full clay panels.

• Convenient panel sizes: Maximum size 62.5 x 115cm / 21 kg. Can be managed by a single person for wall mountings and 2 people for ceilings.

• The system includes end panels and connecting panels.

• Flexible modular system: Up to 8 panels can be connected in a row.

• Enough space for built-in sockets. Sockets with a diameter of up to 68mm can be drilled between the pipes.

• Marked pipe course.

• Savings on labour time and labour cost compared to underfloor heating systems due to less cost for the sub-construction.

• Only 40% of the room size is required for the heating panels: the remaining 60% will be unheated clay panels.

• Significantly less dust sweeping than air convection systems.

• In small spaces, no space for furniture or decoration is occupied.


The calculations are based on the following;
The fibre board thickness is 17mm within the clay sandwich see below;

λ = 0.073 W. m-1 .m-1
Overall panel thickness is 31mm.
Makeup is fibre board (17 mm) & clay plaster sandwich 31 mm o/a.

Where λ is the ‘thermal conductivity’

•  R values go up as insulation gets better whilst U values go down. The U VALUE is in essence the reciprocal of the RVALUE . The lower the UVALUE the better.
•  Thermal conductivity has been stated as λ = 0.073 W. m -1 .m -1 (or W/m.K) which in turn implies that the U value (thermal transmittance) is implied by ;
•  R = l/λ where l is the material (see below) thickness of
⇒  R = 0.031/0.073 = 0.42 K.m 2 /W

Where R is thermal resistance

•   The UVALUE is simply the inverse of the R VALUE plus the internal and external convection and radiation heat losses inter alia …
•  I.e. UVALUE = 1/[R VALUE + R si + R 1 + R 2 … + R so ] where the common value of R si is 0.12 K.m2 /W & R so is 0.06 K.m2 /W.
∴ UVALUE = 1/[0.42 + 0.12 + 0.06] = 1.667 W/m 2 .K min
•  The UVALUE would decrease (a good thing!) when you include whatever wall type the
panel is added to
•  For example if the Clayworks clay/fibre-board panel was added to a solid 9” brick
wall (where R9”- BRICK = 1.8 K.m2/W)
∴ UVALUE = 1/[0.42 + 0.12 + 1.8 + 0.06] = 0.416 W/m2.K

If the clay panel is looked at in isolation i.e. without the additional thermal resistances;

UVALUE = 1/[0.42] = 2.38 W/m2.K

Clayworks Clay Board + 10mm of Clayworks clay plaster
With the additional layer of 10mm Clayworks clay plaster applied to the 31mm fibre board
note the following;

10mm Clay (λ) = 0.76 W. m-1 .m-1
               R 10mm CLAY-PLASTER = 0.010/0.76 = 0.0132 K.m2/W
\ Σ UVALUE of 10mm Clayworks plaster + 31 mm fibre board = 1/[0.0132 + 0.42] = 2.37 W/m2.K

For comparison an unfilled 10” brickwork cavity wall (built prior to 1900) will have a U-value of around 2.0 W/m2.K

As a comparison, the calculations give us the U value of a simple cavity wall from the 1800s – it has a U value of 2 so not much better than the plaster panel. Sitting in a house made just from plaster panels you wouldn’t feel much colder than in your average Victorian building.


• Dimensions: 62.5 x 95/115 x 3.1cm.

• Surface area: 0.59m²/0.72m².

• Weight: 17.5kg/panel (= 29.6kg/m²)/ 21.5kg/panel (= 29.6kg/m²).

• Heating pipe: 11.6mm outer diameter – 1.5mm wall thickness.

• Pipe length: 6.5m.

• Clay application: 15mm finished system.


• Fixed with staggered joints on OSB clad walls or timber/metal framed (w = 6cm) studs at 62.5cm centres.

• Fixed on ceilings or to the underside of rafters 31.25cm centres apart.

• On a wall, they can also be fixed to a solid substrate using an adhesive.

• Fixing materials: drywall screws (3.9 x 45mm) or galvanized staples (length 50mm or longer, width 10mm or more, wire gauge 1.4 mm or more).

• Fixing distance: approx. 15cm apart on all tapered edges. On ceilings or the underside of rafters, an additional row through the middle of the length of the panel is required.

Installation overview

We strongly recommend that you contract with an approved installer. The following guidelines are for design and construction planning purposes.


Anywhere within a building except for areas where there is running water. The panels are especially suitable for bathrooms as the clay system absorbs humidity, however they cannot be used within shower enclosures or directly behind a sink as a splash back.

In a kitchen, clay plaster significantly decreases the build-up of grease, which tends to occur over time in all kitchens.


Stud walls
The panels are screwed to studs with a spacing of 62.5cm.

The spacing for ceiling or roof slopes is 31.25cm.

Wood walls
The panels can be screwed to the wall.

Brick walls or gypsum panels
The panels can be glued without plugging


Vapour diffusion resistance μtotal < 7.

Density 9.6 x 10² kg/m³ (average).

Thermal conductivity λtotal = 0.073 W/(m•K); s(d)=0.031m.


Heating performance 80 W/m² (= ca. 48,0/57,6 W/panel) based on a flow temperature of 35°C and a room temperature of 20°C.

Heating circuit

Up to 8 panels or 60m pipe length. The feed pipe should be a 16 x 2 mm pipe and therefore doesn’t have to be added to the total pipe length.


Measurement of sound absorption in a reverberation chamber to EN ISO 354:2003.
Test object: Heating Panel end plate.
Test centre: Lucerne – Technology and Architecture for International Building.
Date of inspection: 20 March 2014.

Examination procedure

Expiry of the measurement: The necessary for the calculation of reverberation times are determined by the method with integrated impulse response (bursting of a balloon): The decay curves are determined by direct recording of the decaying sound pressure level with the netdb PRO 12 channel frequency analyzer. For a valid measurement, the decay curve to min needs be -40 dB evaluable. The measurements are performed on 12 different microphone positions and 3 different sound source positions. The specified in each third reverberation time is the arithmetic mean of 36 measurements. reverberation times are determined with and without test specimen under the same climatic conditions.


Surface of the test object: 10.7 m² air.
Temperature: 18.6°C.
Relative Humidity: 50% r. F.
Barometric pressure: 95807 Pa


Should the panels incur damage, by being knocked by furniture for example, they can easily be repaired by taking out the damaged material and infilling with clay plaster.


Wiring within the panels is not possible but drilling through the panels for lights, sockets and so on is. We recommend running any services behind the panels and marking out locations of any fittings prior to applying the finish plaster. This simply makes it easier as the un-plastered heated panels have the pipe runs marked out on them so you know where to drill. You can drill anywhere apart from where the pipes run. It is not a problem to add further fittings after plastering as there are easy ways to trace the pipes such as spraying water and watching the clay dry first where the heating pipes run.

Backing boards behind the panels

The wood fibre boards are there for stability and added acoustic and thermal performance. The panels can be glued to any flat solid surface such as concrete walls and ceilings but for masonry we would recommend a soft wood subframe which allows for even spacing of screws to fix the boards. The subframe also creates a space to run services.


The same way you would do for any plastered wall, you can put nails and screws in the wall, for heavier items such as built in floating cabinets etc. we recommend plywood backing but we can look at the project in detail and advise.

Is it possible to achieve good enough thermal performance of the external walls to replace the radiators with the wall heating? Highly likely, yes. We can calculate the area of heated wall needed relative to the size of the room(s) it needs to heat up.



Fire Rating

The panels are not yet fire rated. The clay plaster itself is BRE Class 1 fire rated (also fulfilling the requirements for Class 0 as outlined in the Building Regulations).