Insulating your attic: materials to compare before choosing

Polyurethane foam or polystyrene: what are the differences?

Sprayed polyurethane foam is prized for its excellent insulating properties. At a given thickness, it offers high thermal resistance and easily conforms to irregular surfaces. By effectively covering even the smallest crevices, it minimizes thermal bridging and ensures long-term durability thanks to its strong adhesion.

Mineral wool , whether glass wool or rock wool, remains a benchmark for its excellent value. Easy to install, it also provides good sound insulation. However, its performance depends heavily on the quality of the installation. Incomplete application can reduce its effectiveness.

Expanded or extruded polystyrene , on the other hand, is highly resistant to moisture and suitable for exposed environments. However, its low water vapor permeability necessitates adequate ventilation. The best choice therefore depends on the building's characteristics and the specific requirements of the construction site.

Technical criteria to consider

Choosing the right material depends on many parameters.

Thermal performance indicators

The first indicator to compare is thermal resistance (R). The higher this value, the more the material limits heat loss. When available space is limited, Berner polyurethane foam is often the most efficient solution for a given thickness.

Fire resistance also deserves special attention. Mineral wool has an excellent rating, while polyurethane foam and polystyrene may require additional protection depending on applicable regulations.

Points often overlooked on construction sites

Beyond the intrinsic performance of the materials, several field factors influence the final result. Among the elements not to be overlooked are:

• Attic ventilation: essential to avoid condensation, regardless of the solution chosen;
• The continuity of the insulation: any empty or poorly treated space generates a measurable thermal bridge;
• Compatibility with joinery: air inlets, roller shutter boxes and access hatches must be treated with care;
• Compliance with applicable DTUs: DTU 45.11 for the projection of loose insulating products, DTU 45.10 for panels.

These precautions are not minor details . They directly affect the efficiency of the project and the satisfaction of the end customer.

Product quality also makes a difference

The performance of insulation depends not only on the installation technique. The quality of the materials used is just as crucial. A reliable product guarantees consistent characteristics and greater durability. For polyurethane foam, application conditions, such as temperature and humidity, directly influence the result. A high-quality formulation ensures even expansion and minimizes the risk of shrinkage or performance loss.

Professionals therefore favor products designed for intensive use, whether they be fast-setting foams, formulas adapted to low temperatures, or packaging intended for large-scale projects. Combining a suitable material with high-performance products remains the best guarantee of long-lasting insulation.

In conclusion, choosing insulation for an uninsulated attic comes down to finding the best balance between thermal performance, technical constraints, and budget. Polyurethane foam, mineral wool, and polystyrene each meet specific needs.

Reference document: thermal insulation

This file allows you to:

• Understanding the principles of thermal insulation and its impact on the building's energy performance
• Choosing the right insulation materials and techniques for your construction or renovation project
• Identify solutions to improve thermal comfort in summer and winter
• Discover the regulations, financial aid and innovations in the sector
• Explore brands, articles and news dedicated to thermal insulation

👉 Reference file: thermal insulation