The right insulation with underfloor heating ensures 30-50% faster heating and up to 20% less energy consumption. Choose the material that suits your project:
- PIR: Highest insulation value per centimeter, ideal for limited space (80-90 mm thick). Moisture-resistant and durable.
- PUR: Seamless application with sprayed foam, perfect for complex floors. Saves space and prevents thermal bridges.
- XPS: High compressive strength and moisture-resistant, suitable for ground floors or damp areas.
- EPS: Budget-friendly, but thicker layers needed (120-140 mm). Handy for larger surfaces.
Quick Comparison:
| Material | Insulation Value (W/mK) | Thickness (R=3.5) | Moisture Resistance | Cost per m² |
|---|---|---|---|---|
| PIR | 0.022-0.028 | 80-90 mm | Excellent | €18-25 |
| PUR | 0.022-0.028 | 80-90 mm | Very good | €16-22 |
| XPS | 0.029-0.036 | 100-120 mm | Excellent | €12-18 |
| EPS | 0.031-0.038 | 120-140 mm | Good | €8-15 |
Recommendations:
- New construction: Choose PIR for maximum energy savings.
- Renovation: Use PUR with limited height.
- Damp areas: Opt for XPS.
- Budget option: EPS is affordable and easy to install.
A good installation is essential to prevent heat loss and moisture problems. Make a choice based on your floor structure and budget.
1. PIR Insulation
PIR (Polyisocyanurate) has an insulation value of 0.022-0.028 W/mK, meaning that you achieve the same insulation performance with a thinner layer compared to thicker layers of other materials. In renovation projects, an 80 mm thick PIR panel is often sufficient to meet the minimum R-value of 3.5 m²K/W. In new constructions, a thickness of 90 mm or more is usually chosen.
Thanks to the closed-cell structure of PIR, this material offers significant advantages with underfloor heating:
| Property | Advantage |
|---|---|
| Moisture-resistant | Suitable for damp areas |
| High compressive strength | Can bear heavy loads |
| Fire-safe | Complies with strict building standards |
Well-known PIR products like Kingspan Thermafloor TF70 and Recticel Eurothane GP are specially designed for underfloor heating systems. Thanks to their aluminum finish, they deliver excellent performance.
Correct installation is essential for the best results. The panels should fit snugly, and the seams should be sealed with special tape. This prevents heat loss and ensures even heat distribution. On the ground floor, an additional vapor barrier is often required to prevent moisture problems.
While PIR insulation requires a higher initial investment, its thin profile combined with a high insulation value offers long-term savings in energy costs. This makes it a cost-effective choice.
In the next section, we will look at how PUR insulation can offer other advantages.
2. PUR Insulation
PUR (Polyurethane) insulation is known for its seamless application with sprayed foam, in addition to the option of rigid insulation boards. When using sprayed PUR foam, the material is applied directly on-site, resulting in a completely seamless layer without thermal bridges. For underfloor heating, a layer of 30-40 mm is usually sufficient to achieve the desired R-value.
| Property | Value |
|---|---|
| Minimal thickness | 30-40 mm |
| Compressive strength | Very high |
| Moisture resistance | Excellent |
| Lifespan | 50+ years |
The installation of PUR insulation requires certified professionals. The costs for sprayed PUR range from €25-€40/m² (excluding board materials), depending on the chosen thickness and method.
PUR insulation offers clear benefits for underfloor heating systems:
- Seamless insulation prevents thermal bridges.
- High compressive strength ensures long-lasting performance.
It is important that the substrate is dry and clean before applying PUR. For ground floor applications, using a vapor barrier is recommended.
Although the purchase costs can be higher than some alternatives, the long lifespan and excellent insulation values make PUR a smart choice in the long term. It can save up to 20% energy compared to less efficient insulation materials.
For specific floor constructions, XPS insulation may offer other advantages - more on this in the next section.
3. XPS Insulation
XPS insulation (Extruded Polystyrene) provides specific advantages for floor constructions, especially when there is a combination of heavy loads and underfloor heating. This material is known for its high compressive strength (250-700 kPa) and low thermal conductivity (0.029-0.036 W/mK), making it an excellent choice for such applications.
A notable feature of XPS is the closed-cell structure, which results in a very low water absorption of less than 0.7% by volume. This makes the material highly resistant to moisture, which is essential in many construction environments.
For underfloor heating, a thickness of 50-75 mm is generally recommended. This thickness provides an R-value of 1.7-2.6 m²K/W (with λ=0.034 W/mK). However, to meet Dutch building requirements, additional insulation is often necessary. The panels are available with tongue-and-groove connections, ensuring a good connection and minimal heat losses.
| Property | Value |
|---|---|
| Thermal conductivity | 0.029-0.036 W/mK |
| Recommended thickness | 50-75 mm |
| Compressive strength | 250-700 kPa |
| Water absorption | < 0.7% |
| Lifespan | 50+ years |
During installation, it is important to place a vapor barrier under the XPS panels. This prevents moisture problems and protects the insulation. For water-based underfloor heating, it is recommended to use aluminum heat distribution plates on top of the insulation. These plates enhance heat distribution and increase system efficiency.
The cost of XPS insulation varies from €15-25/m². Although it is more expensive than EPS, XPS offers better performance due to higher compressive strength and excellent moisture resistance. Moreover, the material retains its insulating properties throughout its lifespan, ensuring consistent performance of the underfloor heating system.
For projects with a limited budget, EPS insulation can be an alternative. More about this in the next part.
4. EPS Insulation
EPS, or Expanded Polystyrene, is a popular material for floor insulation in underfloor heating systems. It is known for its favorable price-performance ratio. With a thermal conductivity of 0.031-0.038 W/mK, thicker layers are needed compared to materials like PIR or XPS to achieve the same insulation value.
For underfloor heating, an EPS type with a density of 25-30 kg/m³ is often used. This material provides sufficient compressive strength of 60-250 kPa to bear the load of the floor construction. In renovation projects, a layer thickness of 100-140 mm is usually required to achieve an R-value of 3.5 m²K/W.
| Property | Value |
|---|---|
| Thermal conductivity | 0.031-0.038 W/mK |
| Density | 25-30 kg/m³ |
| Compressive strength | 60-250 kPa |
| Recommended thickness | 100-140 mm |
| Price indication | €8-15/m² |
A major advantage of EPS is its ease of use. The material is lightweight, easy to cut and process. Place the panels with a tongue-and-groove connection, tape the seams, and use a vapor barrier, especially for ground floor slabs.
For better efficiency of your underfloor heating system, you can choose EPS panels with an integrated reflective film. This film ensures more efficient upward reflection of heat. When purchasing, look for certifications and specifications suitable for underfloor heating.
EPS is an affordable choice, especially for projects with a limited budget. Although the insulation value per centimeter is lower than that of PIR or XPS, its attractive price makes it a widely used option. Moreover, EPS is fully recyclable, which contributes to more sustainable projects. Correctly installed, EPS insulation will last at least 50 years.
Material Comparison Table
Here is an overview of the key properties of the materials discussed:
| Property | PIR | PUR | XPS | EPS |
|---|---|---|---|---|
| Thermal Conductivity (W/mK) | 0.022-0.028 | 0.022-0.028 | 0.029-0.036 | 0.031-0.038 |
| Compressive Strength (kPa) | 120-200 | 100-200 | 200-700 | 60-250 |
| Required Thickness for R=3.5 m²K/W | 80-90 mm | 80-90 mm | 100-120 mm | 120-140 mm |
| Moisture Resistance | Excellent | Very good | Excellent | Good |
| Price Indication per m² | €18-25 | €16-22 | €12-18 | €8-15 |
Key Points:
- PIR/PUR: These materials offer the highest insulation value per centimeter, requiring only 80-90 mm to achieve an R-value of 3.5.
- XPS: Combines excellent moisture resistance with high compressive strength. Ideal for applications on the ground floor or in damp areas. Requires a thickness of 100-120 mm.
- EPS: The most budget-friendly option, but requires thicker layers (120-140 mm) to achieve the same insulation value.
As discussed earlier in chapters 1 and 2, PIR and PUR allow for high insulation values with less material. XPS stands out with its high compressive strength and moisture resistance, making it suitable for specific applications such as damp environments and heavy loads. EPS offers a cost-effective solution but requires more space due to its greater thickness.
This table helps determine the best choice for specific situations and serves as the basis for recommendations in the next chapter.
Best Uses and Recommendations
Based on material properties and building practices in the Netherlands, these are our recommendations:
New Construction Projects
For new buildings, we recommend PIR insulation. Practical examples show that using PIR insulation in new buildings can lead to an 18% energy saving. This perfectly aligns with the R-value requirements for new construction (≥4.5 m²K/W).
Renovation Projects with Limited Height
For renovations where the installation height is limited, PUR insulation is an excellent choice. This material offers advantages such as:
- A sprayed variant, ideal for complex floor structures
- A good price-performance ratio, especially for larger surfaces
Damp Areas and Ground Floors
For areas with high moisture risk, such as basements and ground floors, XPS insulation is highly suitable due to:
- The high resistance to moisture and long lifespan
Budget-Friendly Solutions
When there are no space restrictions, EPS insulation is a fine choice. This material is especially handy for attic renovations, upper floors, and DIY projects.
Climate-Specific Recommendations
The Dutch climate, with its moisture and fluctuating temperatures, requires insulation materials that are both moisture resistant and insulating. Here are some recommendations:
| Application | Recommended Material |
|---|---|
| Ground floor | XPS or PIR |
| Upper floors | PUR or EPS |
| Wet areas | XPS |
"In underfloor heating systems, the choice of insulation material is crucial for energy performance. Our practical experience shows that a well-thought-out material choice can lead to an energy saving of 15-20% annually", according to the Dutch Association for Sustainable Building in their 2023 annual report.
It is important to use project requirements and local regulations as a starting point. In doubt? Consult a professional, such as Bricknest, to advise you on the best insulation options for your floor construction and goals.
FAQs
Based on the differences between insulation materials (see comparison table), we answer some frequently asked questions here:
What is the Best Insulation for Underfloor Heating?
PIR and PUR insulation are excellent choices for underfloor heating due to their high insulation value per centimeter (λ-value). With these materials, you achieve the same insulation value with a thinner layer, usually around 80-90 mm, compared to other options. This makes them ideal for situations with limited installation height.
What Insulation Thickness is Needed?
The necessary insulation thickness depends on your project. For the Dutch climate, a minimum R-value of 3.5 m²K/W in renovations and 4.5+ m²K/W in new constructions is usually required for effective underfloor heating.
What Happens with Insufficient Insulation?
Insufficient insulation can cause various problems with underfloor heating, such as:
- Higher energy costs: Up to 25% more energy consumption due to heat loss.
- Slower heating: Takes longer to reach the desired temperature.
- Uneven heat distribution: Possibility of cold spots on the floor.
How to Prevent Installation Issues?
Correct installation of insulation is crucial for a well-functioning underfloor heating system. Pay attention to the following points:
- Use a vapor barrier as recommended with XPS or PIR insulation.
- Place edge strips along the walls to minimize heat loss.
