Insulated Concrete Formwork (ICF) is a modern method of construction that boasts on-site time reductions. It is gaining in popularity in Ireland amid the increasingly urgent demand for housing.
Although the method dates to the 1970s, it has only really gained traction in recent years as more stringent requirements for energy efficiency have come to the fore.
An ICF wall consists of two layers of insulation, which act as the permanent formwork of a concrete inner core and the application of a waterproof render to the outer leaf.
Several advantages
ICF walls offer several advantages over other wall systems commonly used in residential and commercial construction, notably high thermal performance, low hygrothermal risk, and increased on-site productivity. These benefits make ICF a competitive solution to today’s shortage of high-quality, energy-efficient homes.
The nature of this construction method ensures a consistent thermal layer is achieved and is, therefore, self-regulating from an operational energy perspective. In some construction types, thermal bridging and looping can increase heat loss beyond 100% of the design U-value.
ICF reduces these risks by implementing a robust construction process which promotes consistency of the insulation layer, which is an advantage in terms of greater performance guarantee in practice and reducing the performance gap.
However, ICF does face challenges in terms of embodied carbon. While ICF offers thermal efficiency and faster construction, its embodied carbon can be high relative to other building methods. This is primarily due to the relatively high embodied carbon of the monolithic concrete walls.
That said, there are ways to mitigate the embodied carbon of ICF. iStructE Climate Emergency Series set the scene well by stating: “Structural designers should challenge over-specification”. Over-specification can occur in many forms. The best way to challenge it is to do so on a case-by-case basis.
A hidden benefit of ICF lies in its construction process:
- The concrete within the weather line (render) is protected from the environmental risks identified in IS EN 206. Therefore, it could be interpreted as XO class [no risk of corrosion] and relieved of minimum binder contents or maximum water /binder ratio criteria.
- Currently, in ICF construction, IS EN 206 mix designations range from C20/25 to C25/30, but subject to Engineers’ approval, C8/10 may be more appropriate, particularly for housing, given non-monolithic concrete blocks are specified at 4.5 and 7.5 MPa. This would be conservative.
Reductions in the over-specification of concrete lead to cuts in the embodied carbon of the building.
At Altherm ICF, we are pleased to announce that recent research has shown that a concrete mix with 54% less carbon than what is currently being specified has been designed, tested through rigorous laboratory trials, and verified in practice for strength and practical placement. Two alternate (higher strength) options, embodying 37% and 22% less carbon, have also been trialled and tested.
Final thoughts
While ICF may not be seen as a top performer from an embodied carbon perspective, looking through a whole-life carbon lens and considering the potential operational carbon savings, its place as a key technology is worthy of consideration.
While there is currently perhaps an innovation bias toward other concrete technologies, such as 3D printing, the concrete mixtures of those technologies are often burdened with additional technical challenges during the concrete’s fresh life stage, during extrusion, and initial setting – challenges that, to date, are driving cement content up.
In this preliminary research, we observe a reverse challenge for ICF. Although the formwork is different in that it is both permanent and thermally functional, the concrete is “normal.” This “normality” has enabled a seamless rollout of ICF to date and resulted in the use of off-the-shelf mixes optimised for other uses.
Using this research and in collaboration with other initiatives, further optimisation of the concrete mixes could reduce the embodied carbon even further. This research, therefore, calls for continued innovation in the concrete technology space, and we encourage designers and specifiers to embrace such innovation.
Altherm ICF is an award-winning modern construction method designed to address the growing demand for high-quality housing that can be built quickly and at scale.
With the capacity to supply 3,500 homes annually, Altherm ICF offers superior thermal performance, excellent sound insulation, structural durability, and compliance with the latest fire safety standards.
It also provides significant cost savings compared to traditional construction methods, with faster site turnover and lead times of just a couple of days.
Altherm ICF is certified by both NSAI Agrément and the BBA and holds ISO 9001/14001/45001 certifications as a testament to our commitment to quality and continuous improvement.
For more information about our ICF, please visit https://www.altherm.ie