Surface heating

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Logo of the German Institute for Standardization DIN EN 1264
Area technical building equipment
title Heating and cooling systems integrated into the room with water flow
Brief description: Part 1-5
Latest edition 2006-2011
Logo of the German Institute for Standardization DIN EN ISO 11855
Area technical building equipment
title Environmentally friendly building planning - planning, design, installation and control of surface-integrated radiant heating and cooling systems
Brief description: Part 1-5
Latest edition 2015-2016
ISO 11855

The term surface heating is often mentioned in connection with surface cooling. The reason lies in the same suitability and design of the system components. The term surface heating and cooling is therefore used.

Surface heating / cooling is a generic term for various heating and cooling variants that emit or absorb heat via the surfaces of the components of a building.

The individual variants are structured as follows:

Advantages of surface heating

Surface heating increases thermal comfort by warming the surrounding areas. The low system temperatures required for this ( low-temperature heating system ) make them particularly suitable for modern condensing technology , heat pump heating and when used in conjunction with solar thermal energy .

Design of surface heating / cooling

The EN 15377 defines for the interpretation of the following heat transfer coefficients determined:

Type of heating Output
[W / (m² · K)]
Ceiling heating 6th
Underfloor cooling 7th
Wall heating : 8th
Underfloor heating 8-11 depending on the surface temperature, see calculation of underfloor heating

However, the above values ​​are only a first approximation, because the heat transfer coefficients are functions of the exact position of the surfaces in the room and, above all, the surface temperature above or below the room temperature, which in turn is to be formed from the air temperature and the radiation temperature. Definitions of these quantities can be found in detail.

Interface coordination

When installing surface heating or cooling, it is important to act across all trades, in both new and existing buildings. The planning and execution work by the architect, planner, heating engineer, drywall builder, screed layer, top floor layer and, if necessary, other parties involved must interlock directly.

The Federal Association of Surface Heating and Surface Cooling e. V. (BVF): Together with many other associations, two pieces of technical information on "Interface coordination for surface heating and surface cooling systems" were published, relating to new buildings and existing ones. They supplement the applicable standards and technical rules. The individual fields of activity are clearly defined, the areas of responsibility clearly delimited. The individual planning and work steps are documented with the integrated checklists and protocols. The brochures serve as a useful tool for planners, construction workers and supervisors in their activities.

Performance calculation

Main article: Calculation of underfloor heating

The simplest, but still quite precise, is the power calculation with the help of the so-called basic characteristic curves, as they have proven themselves for underfloor heating and are specified in EN 1264-2 . Based on this representation, the basic characteristics for heating and cooling with ceilings, walls and floors have been derived. In the case of wall systems, a distinction is made between active surfaces on inner walls and outer walls because of the widely differing radiant heat flows.

If the heat transport in the room is simulated with thermal room models, the convection heat flow between the thermally active surface and the air and the radiant heat flow between the room surfaces are usually determined separately. The respective radiation component then follows immediately from the separately determined heat flows. Furthermore, the thermal comfort parameter "radiation temperature asymmetry" can be determined.

Subsequent hydraulic balancing

The hydraulic balancing of a surface heating system is necessary to ensure efficient operation. In the case of existing systems in particular, however, there is often a lack of implementation documents or the length of the heating circuit and the existing spacing of the heating pipes are not known. For these cases, the Federal Association of Surface Heating and Surface Cooling e. V. (BVF) has developed a free guide consisting of instructions, a heating circuit table and a form to determine the pump delivery head.

The document describes a method to be able to carry out hydraulic balancing for a large number of typical systems with sufficient accuracy: a rough calculation method by determining the individual heating circuit water quantities. This approximation method is based on the assumption that in many typical cases the construction year of the building can be used to determine the specific heating load. Guideline values ​​can also be assumed for the spread. The flow rate per circle results from the respective area; the pump delivery head is designed after determining the total amount of water. On the system side, heating circuit distributors with adjustable flow meters or adjustable automatic flow controllers are required for this.

Radiation share of different surface heating systems

The radiation component of the heat transfer coefficient inside buildings in the temperature range from 15 to 30 degrees is approximately 5.5 W / m² / K ( EN 15377). This applies to all heated areas, the physical basis for this is the Stefan-Boltzmann law . Values ​​that are above this value mean that the heat is also given off via convection . Based on this, the ceiling heating has the highest proportion of radiation (92%), followed by the wall heating (69%) and the underfloor heating (50% - 69%). For comparison: panel radiators without convectors have a radiation component of around 50%, whereas pure convectors only have around 10%.


  1. Bernd Glück: "Definitions of the operative room temperature (perception temperature) and the radiation temperature of the environment"
  2. Bernd Glück: "Deriving basic characteristics of thermally active surfaces in rooms (see LowEx_Report p. 29ff)" .
  3. Bernd Glück: "Dynamic (thermal) room model" .

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