Chris Stride from the Insulating Concrete Formwork Association explains why this type of modern method of construction could provide the answers for your self-build when it comes to speed, efficiency and air-tightness
Building your home can be a challenging task. Obviously, you want to make the best choices but with a multitude of design and product decisions available, it can be hard to know where to start.
As construction technologies advance so does your choice of techniques, especially in the area of MMC. This umbrella term covers any non-traditional construction system that typically offers numerous benefits including a reduction in construction time, improved energy efficiency and increased build quality.
Self-builders, fully aware of the numerous benefits MMC can offer, have led the way in adopting these innovative methods. It’s worth doing your research to find out which technique is best for you. There are a wide range of methods available, including offsite manufacturing and also innovative onsite techniques such as ICF.
An insulated solid wall construction method like ICF can offer numerous additional advantages when compared to other modern methods. This tried and tested construction system has been around since the Second World war when a simple build method was needed for rebuilding various badly bombed European cities.
Today, the application method and materials remain largely the same. Typically, two panels of insulating material connect to create a building block structure (these are either a pre-moulded form or connected through plastic ties). Concrete is then poured into a cavity between the panels which creates an incredibly airtight, energy efficient and resilient structure.
BUILDING WITH ICF
It is the simplicity of ICF that makes it particularly appealing and incredibly fast to work with. A standard, single-storey structure can easily be constructed in as little as three days!
This method also has a lot of similarities to traditional construction methods that contractors will already be familiar with. The ICF blocks are stacked, like blockwork or bricks, but instead of needing a bedding material such as mortar they instead lock via a raised profile along the edge of the formwork. The walls are usually built in stages, typically to a ground floor height at first, before concrete is poured into the blocks. The process repeats until full building height is achieved.
WILL ICF RESTRICT MY DESIGN?
Despite their dimensions, ICF blocks have the capability to create almost any design – from a traditional farmhouse through to a contemporary home with bespoke shapes or curved walls. This gives you and your architect the opportunity to set your creativity free! We would always recommend getting your supplier involved at this stage in the process – they have the expertise and technical resources to maximise the potential of your ICF.
Concrete is well known for delivering an incredibly strong build. ICF offers the additional advantage of allowing the concrete encased within the formwork to set quickly but cure very slowly, and tests have shown that an ICF building is around five times stronger than a concrete block structure.
Combining the ICF with steel rebar increases the overall strength of the structure making it suitable for the entire build, including cantilever structures
When you consider the entire process, ICF presents a very cost effective option. Upfront material costs may be slightly higher, but these are quickly offset by savings made during construction, and through ongoing energy savings once you’ve moved in.
Labour costs are reduced by the speed of the ICF build programme and usually fewer contractors are needed onsite. The insulating property of the blocks allows the build to continue through winter with the ability to assemble and cast in most weather conditions. The combination of these factors can result in labour cost savings of up to 60%.
At first glance ICF doesn’t appear to be a particularly sustainable build method due to the extensive use of concrete. However, the concrete industry, through the UK Concrete Roadmap it has developed, is working hard on the adoption of new methods with the aim of removing more carbon from the atmosphere than it produces.
When considering sustainability, a recent report by the Environmental Audit Committee ‘Building to net zero: costing carbon in construction’ encourages the adoption of Whole Life Carbon (WLC) assessment. This offsets the amount of carbon created during construction over the emissions created in heating or cooling the building.
ICF’s ability to combine insitu concrete walls sitting in direct contact with the insulating formwork maximises airtightness and thermal efficiency, meaning it can deliver U-values down to as low as 0.10 W/m2.K. Monitored energy usage of a semi-detached four-bedroom home with a basement with a usable floor area of 110 m2 demonstrates that heating and hot water costs works out as little as £5 per week.
BUILDING IN A FLOOD RISK ZONE
Increasingly, the UK is seeing the
effects of adverse weather events.
Under BS 85500:2015 Flood Resilient Construction guidance, ICF is a recommended external wall method. If correctly designed and installed, the resulting concrete structure has no voids and creates a watertight shell. In the event of flood damage, the insulating material in the walls remains water resistant with months of delays caused by drying out avoided.
The insulated solid wall structure also creates its own natural fire suppression system. The solid concrete core will not burn and can withstand extremely high temperatures that prevents fire from spreading internally or externally. Most ICF walls offer a fire protection rating of up to four hours.
Chris Stride is chairman at Insulating Concrete Formwork Association (ICFA)