The role of XPS insulation in passive house design

Passive design is an approach that harmonises with the local climate to maintain comfortable indoor temperatures. Passive House or Passivhaus is a design standard from Germany that achieves high levels of thermal comfort and energy efficiency by utilising insulation, airtightness, window and door design, and ventilation systems.

Effective passive design minimises or eliminates the need for additional heating or cooling, depending on the location. A home based on passive principles can provide long-term thermal comfort, lower energy costs, and reduce greenhouse gas emissions.

It is most effective to incorporate passive design principles when designing and building a new home, but some passive design features can be added through renovations or home improvements.

One of the fundamental principles of passive design is to seal the building envelope, which is the physical interface between the conditioned interior environment and the unconditioned outside environment of a building, also known as thermal bridging.

Insulation is a vital part of any passive-designed home, helping to keep heat inside in winter and outside in summer. The performance of insulation products is measured by how well they resist heat flow, known as their R-value. The higher the R-value, the higher the level of insulation.

XPS foam has excellent thermal resistance, keeping its R-value stable throughout its life. It is, therefore, outstanding underslab insulation and slab edge insulation due to its high compressive strength, moisture resistance, and durability.

Eliminating thermal bridges

A thermal bridge is the point where the hot or cold air crosses from the inside to the outside or vice versa through floor, walls and roof components.

Due to their high thermal mass, the construction materials most likely to create large thermal bridges include aluminium, steel and concrete. Thermal mass is the ability of a material to absorb, store and release heat, and thermal lag is the rate at which a material releases stored heat. For most common building materials, the higher the thermal mass, the longer the thermal lag.

One common location for thermal bridges is concrete slab edges. By installing XPS board as concrete slab edge insulation, you stop thermal bridges and seal the building envelope. Coupled with XPS insulation in the concrete slab and other measures to seal your home, you’ll effectively create a stable environment all year round.

A well-insulated concrete slab will contribute to the building’s thermal envelope. Learn more in our whitepaper on the role of XPS in energy-efficient building design.

Commercial uses of extruded polystyrene foam

As well as residential applications, XPS boards have many commercial applications, including wall and floor insulation, wall cladding, roof purlins, cool room insulation, green roof barriers, and much more.

XPS sheets are ideal for insulating and protecting green roofs on commercial buildings. Even in extreme weather conditions, Foamex StyroRoof preserves its thermal and physical properties thanks to its high-density cell structure and low moisture absorption. Placed below the soil but above the concrete on a roof, XPS foam sheets can assist with creating a thermal barrier and improving the energy performance of the overall building.

In cold storage, XPS board is commonly used as floor insulation due to its stable and predictable thermal conductivity and moisture resistance. Thermal efficiency is essential for decreasing the load on refrigeration equipment and reducing energy use in all types of commercial cold storage applications. Compressive strength is also crucial as insulation for cold storage floors must withstand the weight of material handling equipment, stored goods, stress from racking and the weight of the commercial building.

Sustainable building materials – XPS insulation

Polystyrene products often get a bad rap, which is entirely undeserved because they are manufactured and recycled sustainably, as well as their role in creating a more energy-efficient home or commercial building.

XPS products in Australia are manufactured using up to 100% recycled polystyrene diverted from landfill. The manufacturing process is low-polluting and energy-efficient.

XPS foam like StyroBoard XPS is favoured for its high compressive strength. It meets critical structural and civil engineering requirements because it is dimensionally stable, organically inert and practically impervious to water.

With superior compressive strength and higher long-term R-values, XPS foam board is suitable for use on floors subjected to engineered loads and constant traffic and insulation for inverted roofs, rooftop gardens, parking decks and commercial purlin roof spacers.

Foamex manufactures XPS products in Australia and adheres to strict standards regulating the use of blowing agents. Buying XPS made offshore is accompanied by a risk that the product was made in a country that does not regulate the use of environmental pollutants in XPS products. Toxic input materials may be used to improve the thermal value of different building products. Still, the product may continue to pollute the environment after installation via natural off-gassing over the lifetime of the building. The manufacture of XPS also creates minimal pollution, as the energy used to produce the products comes from steam and water. Over an extended period, the energy efficiency payback of insulation with high R-values exceeds the energy used to manufacture the product.