Insulating concrete forms can provide a wide range of environmental benefits – not least Passivhaus levels of insulation and airtightness. Nudura identifies the key areas of consideration for specifiers.
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Airtightness and thermal performance and are central to the environmental performance of insulating concrete formwork. The standard Nudura wall system, comprising a 102mm internal concrete core, EPS formwork (2x67mm) and applied interior and exterior finishes, gives a tested U-value of 0.23W/m²K. U-values of 0.21, 0.18, 0.14 and 0.11 can be achieved using the company’s Plus product.
Graph showing stabilising effect of thermal mass on internal temperature
“Nudura wall systems are able to meet and exceed UK Building Regulation and the Passivhaus requirements easily and cost effectively”, says Nudura’s International Sales & Business Development Director Jean-Marc Bouvier. “What’s more, this form of construction can save building owners up to 70 per cent in energy costs compared to traditional building methods. The total energy consumption for schools constructed with ICF can be as low as 40-50kWh/m²/yr. This kind of performance can be achieved with a U-value of only 0.24W/m²K, as the system incorporates high levels of thermal mass and airtightness, while avoiding cold bridging.”
Air permeability has been tested as low as 0.33 m³/hr.m² or 0.18 ACH at Woodside School in London
Closely connected with thermal performance is airtightness. Analysed both onsite and in laboratory testing, Nudura’s 152mm form provides a maximum air leakage of 0.117l/s/m² under a pressure of 8mm water. On-site air permeability tests have resulted in figures as low as 0.33m³/h.m² at 50 pascals or 0.2 ACH at 50 pascals. PHPP and Code for Sustainable Homes levels 4, 5 and 6 require maximum air leakages of around 1m3/h.m² and 3m³/h.m² at 50 pascals respectively. By eliminating gaps and draughts, ICFs create airtight structures that maximise the efficiency of mechanical heating, cooling and ventilation systems. This can result in healthier living and working environments for building occupants.
Nudura’s EPS insulation does not contain, emit or use in its production any CFCs, HCFCs or VOCs
Materials and waste
A criticism that has been aimed at ICF is that its principal components – concrete and expanded polystyrene – are derived from fossil fuels. In defense of this, Bouvier points out that only 0.1 per cent of a barrel of oil is used to make polystyrene. More importantly, for every litre of oil used to make EPS insulation, the product can save around 200 litres in reduced heating requirements. In addition, Nudura’s EPS insulation does not contain, emit or use in its production any CFC (chlorofluorocarbons), HCFCs (hydrofluorocarbons) and VOCs (volatile organic compounds), making it non-toxic and environmentally safe. It is also zero-rated for ozone depletion and global warming potential (ODP and GWP). For assembled walls, the ratings are zero ODP and <5 GWP.
More than 50 per cent of the product by weight comprises recycled material. Nudura’s central folding web design is manufactured from 100 per cent recycled polypropylene and steel, while all parts of the system are recyclable at the end of their life. The manufacturer says that its products contribute to a proven 50 per cent reduction in waste compared to conventional cavity-block construction. Furthermore, projects that are designed to Nudura product dimensions can reduce on-site waste to as little as one per cent.
According to ICF Builder, life-cycle assessments comparing ICFs to other building materials show that they outperform these in nearly every region and type of construction. LCA studies indicate that in- use operation, including heating and cooling, account for the majority of a building’s environmental impact over its lifetime (up to 90 per cent). ICF’s ability to combine in-situ concrete walls with permanent EPS formwork maximises airtightness and thermal effieciency, resulting in significantly reduced energy/environmental costs and long life expectancy.
ICF construction combines long life expectancy with high levels of thermal mass and airtightness
Published in 2002, a Portland Cement Association (PCA) funded report entitled ‘Life-cycle assessment of an insulating concrete form house compared to a wood frame house’, evaluates two 220-square-metre dwellings – identical, except for the exterior wall cladding and HVAC system, (which was smaller in the ICF house) – modelled in five climatically diverse cities (Phoenix, Miami, Washington DC, Seattle and Chicago). According to the summary, “The results show that in almost all cases, for any given climate, the environmental impact in each category is greater (worse) for the wood house than for the ICF house. The largest impacts are in the form of depletion of fossil fuel reserves (categorised as damage to natural resources) and release to the air of respiratory inorganics (categorised as damage to human health). Among the construction products used in the house, wood products and copper tubing have the largest environmental load, followed by cement-based materials.”
For more information on Nudura ICF systems please visit the website.