Insulating concrete formwork (ICF) uses hollow, lightweight insulation forms that are fitted tightly together, which are then filled with concrete. Since the concrete sets in direct contact with the insulation, it delivers an airtight reinforcement that prevents thermal bridging. With a demand for greater energy-efficiency, ICF offers quick build speed and high performance standards that more builders are looking to incorporate.
Studies have shown that gaps in insulation can dramatically undermine U-values. Insulation testing of a cavity wall with 50mm of XPS insulation in the cavity – with a 10mm gap to the inner leaf and 40mm gap to the outer leaf – showed that a 3mm gap between the insulation boards increased the U-value from 0.34 to 0.54 W/m2K, whereas a 10mm gap increased it to 0.65 W/m2K, as the thermal performance was undermined by natural convection.
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