Chris Stride at ICFA discusses why self-builders, particularly those looking to maximise energy efficiency, should consider building with Insulated Concrete Formwork (ICF)
If you’ve been researching your new build project recently you will notice that the spotlight is currently on the building industry to help tackle the global climate crisis. When you consider that heating and powering buildings currently account for 40 per cent of the UK’s total energy usage, it is easy to see why improving energy performance within the home has become such an important issue.
Responding to the 2019 consultation on Future Homes Standards, the Government has recently proposed changes to Part L (conservation of fuel and power) of the Building Regulations.
This will ensure that by 2025 all newly built homes will be zero carbon ready and produce at least 75 per cent fewer carbon emissions than those built to current energy efficient standards.
The new performance standards and measures will look to adopt what is called a ‘Fabric First’ approach. Buildings designed and constructed using this approach aim to maximise the energy efficiency of the building through high quality insulation to achieve low U-values and increase airtightness.
The upcoming changes in standards and specifications can seem a daunting prospect for self-builders but there are solutions on the market, such as Insulated Concrete Formwork (ICF), where energy performance is ‘built in.’ Quick to construct with high levels of performance and durability, ICF has been gaining popularity in the UK for some time.
The method combines the insulating material of a hollow formwork or block which is then filled with concrete to create a solid, monolithic core that is incredibly energy efficient. The most common ICF systems supplied in the UK are made with either Expanded Polystyrene (EPS) or woodcrete, a recycled wood fibre bonded with cement. The easy-to-handle blocks are stacked, initially to first floor height, and interlock without the need for an intermediate bedding material, such as mortar, before concrete is poured into the cavity. This process continues until full building height is achieved.
IT’S NOT JUST ABOUT U-VALUES
With ICF systems the formwork stays in place providing thermal insulation on both sides of the building envelope.
Combined with the strength of the concrete core homeowners can achieve U-values as low as 0.10 W/m2.K.
Of course, achieving the target U-values and creating an energy efficient home is not only about the level of insulation used. Solid concrete wall construction of this type also ensures good levels of airtightness – as low as 0.33 mÑ/hr.mÇ or 0.18 ACH – and superior thermal bridging performance. This results in even temperatures throughout the structure with reduced draughts and cold spots, enabling the building to stay warm in the winter and cool throughout the summer. An airtight environment also reduces the effects of dust or allergens and studies have shown this will benefit occupants with allergies and chest complaints.
Another advantage for self-builders is the simplicity in the design and construction of an ICF home, which is beneficial for those with limited building experience. ICFA members hold training courses for anyone new to building with their ICF product and these will give you the knowledge, skills and handson experience needed when starting your project.
The lightweight nature of the material means there is little requirement for heavy plant, and the preformed blocks fit together far more quickly than courses of bricks or concrete blocks can be laid, without the time delay in waiting for mortar to harden. The blocks are made offsite and transported to site for assembly, and the inefficiencies and delays that can affect onsite construction are minimised. ICF construction can also continue in almost all weather, even through the wet winter months.
Building with ICF is a proven way of creating an energy efficient building that is impact and weather resistant, requires little maintenance and offers fire resistance of up to four hours. The system can be used for work above and below ground, making it an ideal choice for basements or retaining walls.
Even though a home is constructed using large blocks, the number of design possibilities are almost limitless, whether you are looking for a traditional looking farmhouse or a contemporary home. A wide range of external facing materials can be applied to achieve your preferred look, including brick, stone, render and timber, as well as steel, aluminium and cement cladding panels.
KNOW YOUR PRODUCT
It’s important to do your research and find the system that is right for you. ICF suppliers have a wide range of standard ‘forms’ which can create dramatic architectural features such as curved walls, vaulted ceilings and cantilevers. In fact, some features are easier to achieve with ICF thanks to the inherent strength of the concrete core.
Get your supplier involved early in the design stage, they have the knowledge and technical resources to support you through your build, and can flag up any areas that may require special considerations.
Systems supplied by ICFA members are recognised by mortgage providers as a ‘standard form of construction.’
There are many companies that offer structural warranties, otherwise known as latent defects insurance, on buildings constructed using an ICF product. It is important to include your structural warranty company prior to commencing the build to ensure you meet your policy’s requirements.
Chris Stride is chairman at ICFA