Robin Miller of Beco Wallform gives his views on why insulating concrete formwork (ICF) is the ideal practical choice for self-builders concerned about sustainability and climate change
There is growing recognition – now almost universal – that unless significant action is taken to reduce the harm we are doing to our world, our children will have serious problems to face as temperatures rise and pollution increases. The most recent report by the Committee for Climate Change (CCC) is quite blunt – if we don’t change our current wasteful ways, the prospects beyond 2050 are pretty catastrophic!
A significant proportion of self-builders have decided to make changes for the better, perhaps inadvertently, because they know they can build a better, more attractive home than is generally offered in the market. Investing in higher performance standards reduces running and maintenance costs and raises comfort standards within the home. Better insulated homes require less heating and it is no surprise to find that the majority of Passivhaus projects are designed by and for self-builders, as they seek to eliminate heating (or cooling) costs which continue to rise.
The ‘fabric first’ approach to energy efficiency is now recognised as the most practical means of reducing heating/ cooling demand in buildings. A ‘passive’ building fabric has no running, maintenance or replacement costs to consider when it comes to future bills. It eliminates heating/cooling equipment and creates a stable, comfortable environment in the home.
This is where insulating concrete formwork (ICF) comes into its own. Systems use lightweight moulded hollow blocks of expanded polystyrene interlocked to form a wall. The hollow core is then filled with concrete which quickly cures to create a very strong structure. What was the formwork to contain the concrete now becomes a complete envelope of insulation for the building, with the insulation on the face of the wall where it is most effective. The thickness of the insulation varies to suit energy performance and the concrete may be reinforced to cater for more demanding structures, basements etc.
One of the easiest and most readily available solutions for responding to climate change is to increase the level of thermal insulation in buildings to passive – or even Passivhaus – levels. ICF construction can provide these high levels of insulation without the need to add extra layers of material which add time and cost to the project. The Wallform ICF system is approved as a Passivhaus building system, meaning that the design and integration of the formwork components do not require additional materials to perform to the Passivhaus standard.
Providing a strong, highly insulated structure makes it easier to develop the building interior using timber or solid floors and partitions, with services recessed into the insulation prior to the direct application of plaster or dry linings. The loadbearing strength of the concrete also allows for more open plan design and flexibility to adapt internal layouts to suit changing lifestyles. Plastic plugs are used for general wall fixings and the concrete core is always available to cope with heavyweight items.
ICF construction is appealing to self- builders because the concept is simple, with only a limited number of components required to build it using a handsaw, without the need for specialist equipment. The building process is quick, and if there is a mistake it is easy to rectify – as long as the concrete hasn’t arrived! ICF suppliers provide training to first time users whether self-build or trade, and there is a national network of experienced ICF builders which is growing to meet rising demand.
There is also a broad choice of ICF systems available, many of them imported from Europe or North America, but several are manufactured in the UK. At the base level the components may be delivered flatpack, as ties, panels and accessories, that are slower and more complicated to assemble and erect.
At the other end of the spectrum a limited number of three or four components are all that are required to interlock, without adhesives, into the formwork construction.
A successful concreting operation is the proof of any formwork system. This may be completed in several stages, filling small sections of wall at a time, but most projects hire a pump to handle the heavy weight of the concrete which is to form the building structure. In a very short space of time an entire storey height pour can be completed, with temporary propping to hold the formwork in position until the concrete has set.
The speed of construction for ICFs is much the same as for offsite frame systems, except ICF delivery lead times are much shorter, allowing much more time for design changes to meet individual client requirements. Frame systems are erected onsite very quickly, but there is still much work to be done before they reach the same stage of completion as an ICF building, since insulation, membranes, sheathing and sealing for airtightness, still have to be completed.
So, you have a strong, durable, energy efficient ICF home which will counter the effects of climate change, but is it sustainable? What about the carbon footprint?
Overall, it is estimated that the energy required to manufacture and build an ICF house is recovered in around 11-13 years of its occupation. Given that the anticipated useful life of an ICF home is considerably longer than alternative methods of construction, this leaves a very small carbon footprint – and the materials can always be recycled for a new generation of homes.
As building standards are upgraded to counter the impact of climate change, the economics of construction will increasingly favour ICF systems that are already proven and available as a versatile solution for the self-builder and new homes.
Robin Miller is MD at Beco Wallform