What Is ICF?
Insulated Concrete Formwork (ICF) is a construction method in which permanent formwork blocks — made from expanded polystyrene (EPS) foam — are stacked to create wall forms, reinforced with steel rebar, and then filled with concrete. The EPS remains in place after the concrete cures, providing continuous insulation on both sides of the structural concrete core. The result is a wall system that combines the structural mass of concrete with very high thermal insulation values.
ICF has been used in North America and Europe for decades and is growing in adoption in New Zealand, driven by increasing awareness of the system’s performance advantages and the availability of New Zealand-specific products and training.
Performance Advantages
ICF construction offers several performance advantages over standard light timber frame:
- Thermal performance: The continuous insulation eliminates thermal bridging through framing members, and the thermal mass of the concrete core moderates internal temperature fluctuations
- Airtightness: Monolithic concrete construction is inherently more airtight than framed construction, reducing heat loss through air infiltration
- Acoustic performance: The mass of the concrete wall provides excellent sound attenuation
- Durability: Concrete walls are not susceptible to the rot and durability failures that have affected some NZ timber frame construction
- Fire resistance: Concrete provides inherent fire resistance without the need for additional fire protection
NZ Adoption Challenges
ICF adoption in New Zealand faces the same challenge as any alternative construction system: the industry’s familiarity with timber frame means that ICF requires investment in training, tooling, and systems change. Building consent authorities less familiar with ICF may require additional documentation. And the initial build cost of ICF is typically higher than timber frame, even though the lifetime operating cost advantage (from lower heating costs) can justify the investment. Builders who develop ICF capability and can explain these trade-offs to clients are well positioned in a market segment that is likely to grow.