Radiant floor heating

Surface heating refers to a heating system in which heat is not emitted via individual radiators, but rather over a large area through pipes integrated into floors, walls, or ceilings. The best-known example is underfloor heating; other types include wall heating and ceiling heating. Surface heating systems operate at low flow temperatures and are therefore particularly efficient when combined with heat pumps.

Structure and Function

Surface heating systems consist of a network of plastic or composite pipes (usually polyethylene or PEX) through which hot water (flow temperature 25-45 °C, depending on the system) circulates. The heat is distributed evenly across the entire surface and warms the room through radiation and convection.

Types:

Type	Location	Flow temperature	Special feature
Floor heating	In the screed	25-40 °C	Most comfortable feeling of warmth, slow response
Wall heating	In the wall	28-40 °C	Faster response, saves on screed
Ceiling heating	In the ceiling	28-35 °C	Even radiant heat, barely visible
Electric underfloor heating	In the screed (cables)	Direct heating	Only practical for small areas (bathroom)

Advantages and Disadvantages Compared to Radiators

Advantages of surface heating:

• Even heat distribution, no feeling of cold due to drafts
• Low flow temperatures = ideal for heat pumps and solar thermal systems
• No space taken up by radiators → more design freedom
• Hygiene benefits: less dust stirred up by convection
• Summer operation possible: cooling via cool water (surface cooling system)

Disadvantages of surface heating:

• High installation costs (screed thickness, piping)
• Slow response time with underfloor heating (heating-up time 1-2 hours)
• Retrofitting in older buildings is complex (screed height increase or thin-layer system)
• Limited furnishing options with wall heating

Surface heating and the Building Energy Act (GEG): Relevance when replacing heating systems

Since 2024, the Building Energy Act (GEG) has required that newly installed heating systems must be powered by at least 65% renewable energy. Heat pumps-the preferred solution for this requirement-work most efficiently in combination with radiant heating. The reason: Heat pumps achieve the best seasonal performance factors (SPF) at low flow temperatures (below 40 °C), while radiators often require flow temperatures of 55 to 70 °C.

Anyone who owns a house with radiators and wants to install a heat pump should check whether the radiators are sufficiently sized for lower flow temperatures or whether underfloor heating should be retrofitted. In many cases, well-insulated older buildings can also be operated with optimized radiators at flow temperatures of 45 to 50 °C-a case-by-case assessment by a heating contractor is recommended.

Radiant Floor Heating as a Cooling System

An often-overlooked advantage: Radiant floor heating can also be used for cooling in the summer. Cool water (approx. 18-20 °C) is circulated through the floor pipes and draws heat from the room via the cool radiant surface. This so-called “surface cooling system” or “natural cooling” can be combined particularly efficiently with a geothermal heat pump, which transfers heat directly to the ground. Together, this creates a year-round efficient system for heating and cooling without the need for additional air conditioning.

Practical Tip for Homeowners in Nuremberg and Franconia

In our consultations, we are seeing more and more often that surface heating systems are considered a decisive purchasing factor for new-construction properties in Nuremberg and the metropolitan region-especially when combined with an air-to-water heat pump, which will be the standard heating solution for new buildings under the GEG 2024. Anyone buying an older home in Nuremberg and wishing to retrofit a heat pump should first check whether underfloor heating can be installed: In many Wilhelminian-style buildings, a surface-mounted system (thin-bed system, approx. 25 mm installation height) is possible. We recommend consulting an energy advisor from the Bavarian Consumer Center network or the BAFA list. The investment in underfloor heating pays off in the long term through lower heating costs and a higher energy efficiency rating-which also positively impacts the achievable selling price of the property.

Frequently Asked Questions

Can I retrofit underfloor heating in my older home in Nuremberg?

Yes, this is possible in many cases. There are special thin-bed systems (starting at approx. 25 mm installation height) that can be installed without the need for extensive screed removal. A prerequisite is a sufficiently insulated floor slab or basement ceiling to prevent heat from escaping downward.

Which floor coverings are compatible with underfloor heating?

Basically all common floor coverings: tiles (ideal, best heat conduction), natural stone, laminate and hardwood (labeled “suitable for underfloor heating”), vinyl, and engineered flooring. Sensitive woods (e.g., solid wood 20 mm or thicker) react to fluctuating humidity and temperatures-follow the manufacturer’s recommendations in these cases.

How high are the heating costs for underfloor heating with a heat pump?

Heating costs depend on the building, the quality of insulation, and the price of electricity. As a guideline: A well-insulated single-family home (150 m²) with an air-to-water heat pump and underfloor heating requires approximately 3,000-5,000 kWh of electricity per year for heating. At an electricity price of €0.30/kWh, this would amount to €900-1,500 in annual heating electricity costs.

How slow is the response of underfloor heating to temperature changes?

The response time depends on the screed thickness and the system temperature. Typical heating-up times range from 1 to 4 hours. Modern control systems compensate for this lag through predictive control (weather-compensated control)-the system heats up early based on the outdoor temperature, not only once it gets cold.

What does it cost to retrofit underfloor heating in an older building?

Retrofitting underfloor heating involves varying levels of effort, depending on the chosen system and the condition of the existing floor. The classic wet screed system (approx. 80 mm installation height including insulation) offers the best performance, but requires significant renovation work: door thresholds must be adjusted, doors shortened, and, if necessary, drain connections relocated. The cost is around 60 to 90 euros per square meter, plus the cost of the screed and flooring. Dry systems (studded panels without wet screed) are significantly less involved; they require an installation height of only 25 to 40 mm and work well in well-insulated older buildings. The cost here is 40 to 65 euros per square meter. In older Nuremberg buildings with post-war concrete ceilings, retrofitting is often possible; for historic wooden beam ceilings-typical of buildings constructed before 1930-structural inspections and, if necessary, reinforcement measures are required beforehand. We recommend always making the decision to install underfloor heating in conjunction with the overall renovation strategy and the planned heating system.

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