Insulating Concrete Formwork (ICF)

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Insulating concrete formwork (ICF) is a construction method where concrete is poured inside polystyrene to form the structure. The polystyrene is left in place to provide a thermally efficient building. ICF is proven to be a robust, cost-effective method of constructing a variety of building types from houses and basement to multi-storey commercial buildings.

ICF consists basically of twin-walled extruded (XPS) or expanded (EPS) polystyrene panels that are built up to create the walls of the house or other building. This formwork system is then filled with ready-mixed concrete to create a structure ready to accept the roof or floor construction.

We recommend the use of the XPS system for the following reasons: Thermal – XPS is approximately 25% more efficient than EPS Strength – XPS is up to twice as strong as EPS therefore withstands the pressures of the concrete exerted in the wall. Watertight – XPS is virtually waterproof whereas EPS will allow more water to be absorbed over a period of time.

ICF construction has bee successful for over 40 years, principally in Northern Europe, the US and Canada. In the UK it is growing rapidly as a viable construction method and an economical alternative to traditional construction techniques.

The principal advantages of using ICF for the occupier are:

• Low running costs – the occupants benefit from low running expenses, as the energy-efficient building costs less to heat. In fact, a well-designed house may need no heating other than that provided by solar energy.
  
  
• Good Acoustic performance – the ICF insulation reduces impact sound within the building, while the concrete core provides a solid mass to reduce airborne noise. This makes the system ideal for party wall construction where the concrete core may be up to 300mm thick.
  
  
• Healthy indoor environment – all materials used in the ICF system are inert, so give of no toxic fumes. The building will maintain an even temperature and the air quality are easily controlled with no leakage – good news for asthma or allergies sufferers. Problems associated with condensation, mould and mildew on walls are eliminated.
  
  
• Fire resistance - Internal - Plasterboard is mechanically fixed to the ICF rails to provide the necessary protection against internal fire spread. This can provide fire resistance periods of up to one hour.
  
  
• Flood damage – It is thought that an ICF building subjected to flooding would be more resistant to water ingress and should suffer much less consequential damage than other forms of construction. However as we adopt a belt and braces approach to waterproofing this will not be a factor you will have to worry about.
  
  
• Mortgage, insurance and planning acceptance – All mortgage lenders, insurance companies and planning authorities accept ICF construction.

The advantages of using ICF for a sustainable environment are: Superior thermal performance – the combination of the polystyrene insulation and the in-situ concrete easily produces a robust building with a U-value of between 0.14-0.27 W/m2K (depending on wall thickness), which is within the current Part L. Building Regulations requirement for energy efficiency. High thermal mass – the high thermal mass of the concrete provides a more ‘energy storage’ than other forms of construction. This absorbs and stores heat or coolness, which results in less temperature fluctuation. This thermal stability means that less energy is required for heating or cooling and produces a much more even and comfortable living environment. Waste and recycling – with ICF construction, there is minimal waste during construction and at the end of the building’s useful life the materials are recyclable. Fewer deliveries & less traffic – the use of ready-mixed concrete from a local supplier means that the main construction material has not been imported or hauled long distances, and with only two key materials, the number of deliveries to site is reduced.

ICF and the Basement
ICF is ideal for any basement and retaining wall construction.The wall core would be 200mm, 250mm or 300mm depending upon the structural loadingand the soil pressures.The ICF system that we use has advantages over any other ICF system in basements for the following reasons:

• The formwork is made of Extruded Polystyrene – the most moisture resistant of any insulating board
  
  
• The reinforcement can be welded wire mesh – this saves a lot of construction time over the placing and tying of ordinary reinforcement bar
  
  
• Wide formwork ensures excellent concrete compaction

For more information see our information sheet below on ‘How ICF works’ or contact us for a quotation.

‘How ICF Works’ downloadable 604Kb pdf

ICF Frequently asked Questions