Designing and Constructing with ICF – Part 1

Aug 5, 2019

In the first of this two-part feature, Insulating Concrete Formwork Association (ICFA) considers how architects should approach the design of insulating concrete formwork buildings

Insulating concrete formwork (ICF) can provide significant benefits for construction projects, including high levels of environmental performance, speed of construction and longevity. The system, which is based on in-situ concrete walls cast into permanent, hollow panels of insulation material, usually expanded polystyrene (EPS) formwork, represents something of a departure – in the UK at least – from traditional forms of construction, including cavity walls and framed structures (timber, steel and concrete). With this in mind, the ICFA explores how architects should approach this innovative and energy-efficient form of construction.

Adopting New Methods

One of the most common mistakes that architects make is trying to apply ‘traditional’ construction methods and details to ICF projects. Designers should come to this type of construction with an open mind. It has its own logic and methodology, which when correctly applied, produces excellent buildability, inherent flexibility and almost limitless design potential. The earlier that architects engages with their ICF supplier the better. They can identify areas that may require special consideration, such as large wall openings or overhangs, and advise accordingly. The supplier will also flag-up design issues that are specific to ICF construction. For example, architects do not have to consider interstitial condensation in terms of envelope design, but many need to consider means of ventilation in relation to airtightness, building use and occupancy.

Dimensions and modules

ICF projects can be built to any size, including brickwork dimensions. However, by utilising the formwork module it is possible to reduce build times and virtually eliminate construction waste. The most important element for the designer to consider in respect of plan layouts are the insulation panels located either side of the concrete wall. The building length and width, as well as the overall thickness of the concrete wall must reflect the thickness of both insulation panels. Interior area calculations must take the inner panel into account.

Standard and non-standard details

Detailing is an issue which can be daunting for architects who are new to ICF. The details allow architects to successfully interface a wide spectrum of different construction systems, materials and products. Furthermore, the flexible nature of ICF means that important aesthetic considerations, such as whether to recess doors and windows, and by how much, are easy to achieve using standard detailing practices. Indeed, some conditions, such as corner windows and cantilevered openings, are easier to design with ICF than traditional forms of construction, as they do not require complicated structural solutions. The simplicity of the system also makes it inherently adaptable. Changes to formwork, for example, can incorporated into the design up until the concrete is poured on site.

Floors and roofs

When it comes to specifying floors and roofs ICF walls connect to a wide range of systems, including hollow core planks, OWSJ composite decks, proprietary steel joists and traditional timber joists. As with any form of construction, each typology has its own advantages and disadvantages. Your supplier can advise on compatible systems and how easy or difficult it is to achieve good levels of airtightness. ICF is inherently airtight, so it makes sense to employ a system that harmonises with this approach. Concrete floor and roof decks are the most obvious examples, although these may not be suitable for every project. Again, it’s about adapting to a new building methodology, and maximising the opportunities that it presents.

Reproduced by kind permission of NUDURA and Architecture Today



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