Insulation Boards in Underfloor Heating Systems

Insulation boards in underfloor heating systems prevent heat loss. High-quality boards offer superior thermal performance, significantly enhancing the energy efficiency of the system. Currently, the two main types of insulation boards used in underfloor heating are foam boards (EPS) and extruded polystyrene boards (XPS). So, what are the advantages and disadvantages of each?

Foam Board (EPS)
Foam boards are white panels formed by heating expandable polystyrene beads—which contain volatile liquid blowing agents—in molds after pre-expansion. They feature a fine closed-cell structure.

Advantages:

1. Lightweight:
   In China, the density of EPS boards is regulated to 18–22 kg/m³, while in Europe, it is only 15 kg/m³.
2. Low Thermal Conductivity:
   The air-filled cellular structure impedes air transmission, resulting in a thermal conductivity below 0.039 W/(m·K).
3. Good Impact Resistance:
   With 98% of the volume filled with air, EPS boards can absorb and recover from external impacts effectively.
4. Low Water Absorption:
   Moisture can compromise thermal and mechanical properties, but the low water absorption of EPS helps maintain these characteristics.
5. Recyclable:
   EPS has the highest recycling rate among plastics.

Disadvantages:

1. Complex Installation:
   Installing EPS requires laying mesh reinforcement, which is tedious and prolongs construction time.
2. Low Strength:
   EPS boards are prone to cracking, and detachment of the insulation layer is relatively common.
3. Poor Load-Bearing Capacity:
   Due to limited inherent strength, floor reinforcement is necessary during installation.
4. Unstable Quality:
   EPS boards require a curing period after production before use, making consistent quality difficult to ensure.
5. Flammable and Toxic:
   EPS is highly combustible, and its combustion releases toxic fumes. Even with flame retardants, it can only achieve a Class B fire rating.

Extruded Polystyrene Board (XPS)
XPS boards are manufactured by extruding polystyrene resin and other additives, producing panels with a continuous, uniform surface and closed-cell honeycomb structure. This process overcomes the complex production limitations of EPS and offers irreplaceable advantages:

Advantages:

1. Excellent Thermal Insulation:
   XPS boasts high thermal resistance, low linear expansion, and a closed-cell rate exceeding 99%. Its thermal conductivity of 0.028 W/(m·K) is lower than that of EPS.
2. Superior Moisture and Water Resistance:
   The tight closed-cell structure and inherent hydrophobicity of polystyrene result in extremely low water absorption.
3. High Compressive Strength:
   Depending on the model and thickness, XPS can withstand compressive strengths of 150–500 kPa or higher, maintaining performance even after prolonged water exposure and supporting various floor heating loads.
4. Lightweight yet Rigid:
   The combination of closed-cell chemical foaming and honeycomb physical structure makes XPS durable, easy to cut, and convenient to transport.
5. Durable and Chemically Stable:
   XPS is highly resistant to chemical degradation, moisture, and corrosion, retaining its properties even in high-temperature environments.
6. Environmentally Friendly:
   XPS does decompose, mold, or emit harmful substances. Its production uses eco-friendly materials, causing no industrial pollution.

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