Insulated Concrete Formwork (ICF) is a modern method of construction that consists of hollow, interlocking blocks which are stacked to create a form (mould) for concrete. The blocks are manufactured from an insulating material, often polystyrene. Once the blocks are stacked into the desired structural shape, concrete is poured into the hollow centre. The concrete may be reinforced with the placement of steel bar for structural engineering. The insulating formwork (mould) is retained once the concrete has cured. This provides insulation to both the internal and external faces of the concrete.

ICF properties are definitely sustainable. But let’s be clear about how we are defining sustainability.

So, let’s address the elephant in the room. Concrete isn’t considered to be a sustainable material. Concrete is made up of cement and aggregates. Cement production accounts for circa 7% of the global CO₂ equivalent (greenhouse gasses), annually^{Ref.01}. This is due to the high volume of concrete produced around the world.

UNDERSTANDING THE FIGURES

Current research shows that for every tonne of concrete produced, anywhere between 0.050 tonnes to 0.160 tonnes of CO₂ equivalent (greenhouse gasses) are produced^{Ref.02}. The Concrete Centre have reported an average of 0.072kg CO₂^e/kg which is a reduction of 30% from the 1990 baseline^{Ref.03}. These numbers are useful to compare against other building materials as a comparison.

Sustainable timber actually absorbs carbon from the atmosphere. Current research shows that for every tonne of sustainable timber produced, anywhere between 0.030 tonnes to 0.243 tonnes of CO₂ (equivalent) are absorbed^{Ref.04}. This is therefore an average of -0.137kg CO₂^e/kg, providing the opportunity to offset other emissions within a project. However, these figures fail to include the environmental impacts of deforestation and transport of materials from abroad. It must be noted that not all timber is sustainable. Should timber be sourced from unsustainable deforestation overseas, the true carbon emissions of timber products may vary from 6.35kg CO₂^e/kg to 10.36kg CO₂^e/kg^{Ref.05}. Deforestation currently contributes circa 25% of the global CO₂ equivalent (greenhouse gasses), annually^{Ref.06}. In this instance, concrete would be a more responsible option as the environmental damage would be less.

A SUSTAINABLE BUILT ENVIRONMENT

What’s a more important focus during construction, the use of sustainable building materials or to produce a sustainable property?

Current studies show that only 25% of a building’s energy consumption occurs during the construction stages, with the operation accounting for almost 75%^{Ref.08}. Therefore, the greatest impact to a reduction in carbon emissions can be achieved through the creation of more energy efficient properties. It was reported in 2015 that home energy use accounts for circa 13% of the UK CO₂ equivalent (greenhouse gasses) ^{Ref.07} emissions. This could be significantly reduced if houses were more efficient.

Producing a more energy efficient (sustainable) built environment is a more important focus than utilising sustainable materials.

THE SUSTAINABLE BENEFITS OF ICF STRUCTURES

ICF construction provides long-lasting, airtight, and thermally efficient homes. This “fabric first” approach boasts reduced construction time on site, locally procured materials and reduced carbon footprint of material production when compared with other technologies on the market. Using Fabric First principles may also help to meet the more advanced current and future energy efficiency requirements towards achieving zero carbon and near zero energy homes ^{Ref.09}.

ICF systems are an in-situ formwork creating extremely airtight properties ^{Ref.10}. This benefits from reduced construction times on-site, with detached housing superstructures completed in as little as six weeks (including foundations) by only a team of 2-3 operatives.

The principal benefit of ICF construction is the energy efficiency. The resulting construction offers U-values as low as 0.11W/m²K, beating current Passivhaus standards of 0.15W/m²K ^{Ref.11}. This technology utilises the high thermal mass of concrete by insulating the internal and external profiles with XPS/EPS. Current studies show the lifespan of reinforced concrete far surpasses any other modern or standard methods of construction ^{Ref.12}. With lifecycles spanning centuries, as opposed to decades, ICF reduces embodied carbon from a lowered need for maintenance and longer lifespan.

The design of the property can make use of the ICF block sizes to reduce on-site waste. This furthers the goals of Material Resource Efficiency through optimised use of materials and reduced waste during construction ^{Ref.13}.

Sustainability is measured across 3 sectors: environmental, social, and economic. The table below outlines the sustainable benefits of concrete construction.

Ref.01 – Thomas Czigler, Sebastian Reiter, Patrick Schulze, and Ken Somers, Laying the foundation for zero-carbon cement

Ref.02 – Akan, M. O. A., Dhavale, D. G. & Sarkis, J., 2017. Greenhouse gas emissions in the construction industry: An analysis and evaluation of a concrete supply chain

Ref.03 – The Concrete Centre, 2018. Remixed: How Concrete is Evolving for a Net Zero Built Environment. Concrete Futures.

Ref.04 – BMTrada, 2022. Carbon and timber in construction for building designers

Ref.05 – Weight, D. H., 2011. Embodied through-life carbon dioxide equivalent assessment for timber products.

Ref.06 – P. Moutinho, S. Schwartzman, Tropical Deforestation and Climate Change

Ref.07 – BRE Global, 2018. Home Quality Mark One: Technical Manual (England, Scotland, Wales)

Ref.08 – M. Karimpour, M. Belusko, K. Xing, et al., Minimizing the life cycle energy of buildings: review and analysis, Building and Environment 73 (2014) 106–114.

Ref.09 – Stenlund, S., 2016. Applying Fabric First principles: Complying with UK energy efficiency requirements

Ref.10 – The Concrete Centre, 2010. Insulating Concrete Formwork: A guide to the performace benefits of ICF Solutions

Ref.11 – Hopfe, C. J. & McLeod, R. S., 2015. Passivhaus designer’s manual – a technical guide to low and zero energy buildings

Ref.12 – Tovey, A. K., Roberts, P. J. J. & Kilcommons, M., 2007. Design and Construction using Insulating Concrete Formwork

Ref.13 – Adams, K. & Hobbs, G., 2017. Material resource efficiency in construction: Supporting a circular economy

The UK construction industry is conservative in nature and slow to change. There are many reasons for this.

The industry has a long history of traditional practices and cultures. This has been reinforced by the use of apprenticeships where the transmission of skills and knowledge is through experience.

Also, the industry carries high levels of risk, with large investments and complex projects. This can lead to a risk-averse culture that is resistant to change, as any deviation from established practices could be perceived as risky.

The UK construction industry is highly fragmented, with many different companies and contractors involved in any given project. This can make it difficult to introduce new technologies or processes, as there is no single entity to co-ordinate or manage the change.

The UK construction industry is also heavily regulated, with many standards and guidelines that must be followed. Again, this can make it difficult to introduce new technologies or methods that do not comply with existing regulations or standards.

It is therefore no surprise that modern methods of construction have struggled to find a market in the UK.

ICF construction has a number of performance characteristics that can improve the sustainability performance of a building or structure.

SUSTAINABLE CONSTRUCTION

Sustainability is measured across three “pillars”: Environmental, Economic, and Social.

The environmental benefits of ICF construction can be high energy efficient structures, reduced timeframes for construction, reduced site waste, increased sound insulation, reduced transportation of materials, and increased usage of recycled materials.

The economic benefits of ICF construction can be locally procured building materials, benefiting the local economy, and reduced site labour, reducing overheads.

The social benefits of ICF construction can be higher quality air control against pollutants, reduced noise transference between occupants, and longer lasting, more durable structures for generations to come.

ACOUSTICS

The double insulation of ICF walls, along with the concrete core, creates a high acoustic insulation, significantly reducing noise transference.

This issue of acoustic performance has grown in importance over the past several years. Due to the increased demand from government for increased density in urban dwellings, the number of complaints about noise has risen. This is due both to the closer proximity of properties and ever developing home entertainment systems. For this reason, the UK Building Regulations Part E now requires improved sound insulation.

FLOODING

ICF construction allows for the addition of additives to the concrete mix to provide waterproofing (Type B). This, along with a “Type A” and “Type C” design can create waterproof structures.

New building works within areas of flood risk are only permitted in exceptional cases where the risks are managed and adequate flood defence measures and/or flood resistant construction techniques are adopted. Therefore, the type of floor construction is an important consideration.

FIRE

Concrete does not burn. It cannot be set alight like other materials and does not emit any toxic fumes when exposed to fire. It will also not produce smoke or drip molten particles. For these reasons, in the majority of applications, concrete can be described as virtually ‘fireproof’. Concrete’s airtight construction reduces the spread of smoke. The concrete core of ICF benefits from the ability to maintain the building’s strength during a fire.

EFFICIENCY

Concrete has a high thermal mass which increases the energy efficiency of the structures. Thermal mass refers to the ability of a material to absorb, store, and release heat energy. In other words, it is the ability of a material to hold onto heat and release it slowly over time. Materials with high thermal mass can help to regulate indoor temperatures and reduce energy consumption in buildings by reducing the need for heating and cooling systems.

DURABILITY

Concrete walls have a robust structure that may exceed design requirements. Therefore, the building can accommodate future design and structural changes. ICF is commonly used in residential and commercial properties, where their strength allows for the introduction of concrete upper (and intermediate) floors, making all internal walls below non-load bearing. This design approach allows for flexible layout changes to cater to future living requirements, meeting the government’s requirement for ‘lifetime homes.’

ICF blocks are usually made from polystyrene, either Expanded Polystyrene (EPS) or Extruded Polystyrene (XPS).

EPS is a light-weight foam product. One cubic meter of EPS contains about 10 million beads. EPS is composed of 2% polystyrene and 98% air. Since air is one of the best thermal insulators, EPS makes for an excellent insulation material. This is very budget-friendly, lightweight, easy to process, and is easy to recycle.

XPS is available in rigid insulation boards. The boards have a closed cell structure and come in various compressive strengths, which makes them ideal for numerous applications. For example, XPS boards with a high compressive strength are particularly suitable for insulating structural slabs, rooftop car parks, and garages. XPS is resistant to mould, lightweight and easy to apply without irritating the skin. It is 100% recyclable. XPS is inert as it cannot contaminate the air or water with gases or chemicals. The product benefits from BREEAM A rating. This ensures that specifiers can be sure of scoring with BREEAM points. XPS is also approved by the Green Guide to Specification.

ICF blocks are usually made from polystyrene, either Expanded Polystyrene (EPS) or Extruded Polystyrene (XPS).

EPS is a light-weight foam product. One cubic meter of EPS contains about 10 million beads. EPS is composed of 2% polystyrene and 98% air. Since air is one of the best thermal insulators, EPS makes for an excellent insulation material. This is very budget-friendly, lightweight, easy to process, and is easy to recycle.

XPS is available in rigid insulation boards. The boards have a closed cell structure and come in various compressive strengths, which makes them ideal for numerous applications. For example, XPS boards with a high compressive strength are particularly suitable for insulating structural slabs, rooftop car parks, and garages. XPS is resistant to mould, lightweight and easy to apply without irritating the skin. It is 100% recyclable. XPS is inert as it cannot contaminate the air or water with gases or chemicals. The product benefits from BREEAM A rating. This ensures that specifiers can be sure of scoring with BREEAM points. XPS is also approved by the Green Guide to Specification.

ICF costs between £120 to £190 per square metre to construct. This would include all materials such as concrete, structural steel, etc… The design will determine the type of concrete, the amount, and type, of structural steel and the overall complexity of the project. These factors will be considered when pricing for works. It has been noted that the price of ICF is comparable with that of standard construction methods. There is no industry standard pricing guide. However, we suggest as an average “rule of thumb” to budget £150 per square metre for both insulated slab foundations and ICF walls. It may be more, it may be less. It all depends on the specifications of the project.

ICF construction requires less labour than that of standard construction. An experienced team of 2-3 operatives can erect a lift (storey) of a typical new build house within as little as one week.

The combination of lightweight, easy-to-handle blocks and poured concrete makes ICF a quick, all-weather construction system. ICF installation is not dependant on ‘good weather’. This means NO project stand downs due to weather; even on the frequent, rainy British days.

ICF IN MINUS TEMPERATURES

The insulation supporting the concrete helps to retain heat, when the concrete is placed a chemical reaction between the cement and water (hydration) generates heat and continues too until the concrete is fully cured. This means the concrete placement is unaffected by adverse weather conditions; This allows your project to be unaffected by any weather delays.

MOBILISATION & LEAD TIME

Supply of ICF material can be delivered to site in some cases as quickly as one week However, we would advise to make an allowance of 3-4 weeks from confirmation of your order. What does this mean? From design to on-site delivery can move extremely quickly to meet potentially tight deadlines.

The best way to build with ICF is to contact Bondmor Building Services Ltd to undertake your works. ICF blocks are stacked onto appropriate foundations and held in place with specialist alignment frames. The structural steel is installed, to the engineer’s specifications. Concrete is then poured into the ICF blocks, using a boom pump. Access and mobilisation must be well considered prior to any ICF construction. Once the concrete has been poured and cured, the alignment frames may be removed. It can be quick and easy when you know how. At Bondmor, we know how.

You can use ICF to build below-ground walls/foundations of a home or building. If you are building a basement for accommodation or recreation, you are required to achieve a Grade 3 habitable basement in order to comply with BS8102/22, the British Standard for earth retaining structures. Currently, A minimum of a Type A and C system is the solution for ICF below ground that complies with British standards and insurance backed warranties*

The short answer is most, if not all external finishes are achievable on to ICF. Constructing an ICF house or building allows you to choose from multiple exterior finishes: Render, Masonry slips, cavity Masonry, Wood, Metal and Vinyl cladding to name a few.

ICFs offer fastening points within the system for exterior and internal finishes at varying centres and additional fastening points at the corners.

The exterior finish selection comes down to your budget, local styles, and personal choice.

Passivhaus (Passive House) is a voluntary European standard for assessing, rating, and certifying the sustainability of a building. Passivhaus standards result in ultra-low energy buildings that require little energy for space heating or cooling.

The central principle is that a Passivhaus properties can maintain its internal temperature and air quality, simply, by using a small amount of heating or cooling to the air.

The principles of passivhaus design:

• Highly insulated
• Airtight construction
• Addressing thermal bridging
• High Quality fenestration & doors
• Orientation and shading
• Mechanical ventilation with heat recovery

To find out more please check out the Passivhaus Trust.