Pipe Types Used in Underfloor Heating Systems and Their Differences

Underfloor heating systems have become one of the most preferred heating solutions in both residential and commercial buildings in recent years. The efficiency, durability, and longevity of these systems largely depend on the type of pipe used. Each pipe material offers different properties in terms of thermal conductivity, flexibility, and chemical resistance. In this article, we will take a detailed look at the main types of pipes used in underfloor heating systems and their differences.

PE-RT Pipes (Polyethylene of Raised Temperature Resistance)

PE-RT pipes have become increasingly popular in underfloor heating projects in recent years.

Advantages:
According to a 2014 document published by the Plastic Pipe Institute (PPI), the thermal conductivity of PEX pipes is reported as 0.41 W/m·K, while that of PE-RT pipes is 0.46 W/m·K. These figures show that PE-RT pipes have higher thermal conductivity compared to PEX pipes.

Normally, the desired oxygen permeability value for PE-RT pipes is 0.32 mg O₂/m²·day, whereas KAS PE-RT pipes have a value of only 0.03 mg O₂/m²·day — approximately 10 times lower than the standard value.

• Flexible and lightweight structure allows for easy installation

• Chemically resistant

• Environmentally friendly and recyclable material

• More cost-effective than PEX pipes

• Advanced production methods improve heat and pressure resistance as well as flexibility

• Significantly more eco-friendly compared to PEX products

Over the past 15 years, PE-RT pipes have achieved market leadership in Europe, surpassing other products in usage rate.

European market distribution:

• Copper/Traditional materials: 48%

• PEX-A, PEX-B, PEX-C: 24.7%

• PE-RT: 27.3%

This data shows that PE-RT pipes have overtaken PEX products in market share.

Disadvantage:

• The pipe bending radius is slightly larger compared to PEX.

PE-RT pipes provide an efficient and economical solution, especially for low-temperature heating systems such as residential buildings.

PEX Pipes (Cross-linked Polyethylene)

PEX is one of the most widely used pipe types in underfloor heating systems.

Advantages:

• High temperature resistance (up to 90°C)

• Resistant to corrosion and chemical effects

• Flexible structure allows for easy installation

• Long lifespan with minimal maintenance required

Disadvantages:

• Sensitive to UV radiation and should not be exposed to direct sunlight

• PEX-A pipes require heating during installation in cold climates, which increases labor costs

• Due to a higher cross-linking ratio, installation can be more difficult compared to PE-RT

PEX pipes are generally categorized into three groups — PEX-A, PEX-B, and PEX-C — based on the cross-linking method used in production. PEX-A pipes have the highest temperature resistance.

PEX-AL-PEX Pipes (Aluminum Composite Pipes)

PEX-AL-PEX pipes consist of an aluminum layer sandwiched between inner and outer PEX layers.

Advantages:

• Excellent shape memory — maintains its form when bent

• Low thermal expansion coefficient — minimal deformation with temperature changes

• Oxygen barrier prevents corrosion in metallic components of the system

Disadvantages:

• Requires careful installation; incorrect connections may cause leakage

These pipes are widely used in professional heating projects due to their high temperature resistance and structural stability.

PB Pipes (Polybutylene)

PB pipes were very popular in the past but have largely been replaced by PEX and PE-RT pipes today.

Advantages:

• High flexibility

• Long lifespan

Disadvantages:

• Limited resistance to high temperatures

• Limited availability for new projects

However, PB pipes can still be found in older heating systems that remain operational.

Metal Pipes (Copper and Steel)

Although not commonly used today, metal pipes are still utilized in specific industrial projects.

Advantages:

• High thermal conductivity

• Resistant to mechanical impacts

Disadvantages:

• Rigid and difficult to install

• Prone to corrosion

• May cause expansion-related issues in underfloor systems

For this reason, metal pipes are primarily used in collector connections or specialized industrial applications.

Which Pipe Type Is More Suitable?

When selecting the appropriate pipe type for an underfloor heating system, consider the following factors:

• Building type: residential, villa, factory, warehouse, etc.

• Heat source: boiler, heat pump, solar energy

• Operating temperature: low or high-temperature systems

• Installation conditions: required flexibility and ease of installation

Why Choose PE-RT Pipes?

The EN 22391 Standard defines pipes used in underfloor heating systems and specifically includes PE-RT pipes. These pipes are considered the optimal solution due to their:

• Excellent balance between temperature and pressure performance

• Ease of installation

• Cost-effectiveness

• Environmentally friendly material composition

For high-pressure and high-temperature industrial applications, PEX-A pipes may be preferred. However, their environmental impact and higher cost remain significant disadvantages.

Installation and Application Recommendations

• Pipe spacing: should be determined based on the heating demand of the project

• Pipe diameter: 16 mm is the most common choice

• Layout: spiral (snail) pattern ensures even heat distribution

• Pressure testing: must be performed after installation.

All KAS PE-RT and PEX pipes are factory-tested at approximately 3 bar air pressure before delivery, ensuring both factory and on-site testing reliability for maximum safety and performance.

• Insulation: EPS/XPS insulation boards should be used beneath the floor

The efficiency of an underfloor heating system depends not only on the type of pipe used but also on proper installation practices.

KASTherm PE-RT and PEX pipe systems deliver high efficiency, long service life, and reliable performance — ideal for both residential and professional projects.

Choosing the right pipe type directly affects system performance, energy efficiency, and lifespan. Always seek professional technical advice when determining the most suitable material for your project.

At KASTherm, we help you build the most efficient underfloor heating system with our high-quality PE-RT and PEX pipe solutions.

Contact us to determine the most suitable pipe type for your project.