When looking to use insulated concrete forms in your build, the choice can initially seem overwhelming. Each one follows the same principles of combining an insulating material, typically used as a hollow block and, then in-filled with concrete. All the systems available will offer the same benefits including speed of build, high levels of energy efficiency and cost-effectiveness. However, look into them in detail and there are slight differences, including the size of the blocks, material and insulation levels.
We run through the main types of ICF systems available and explore the benefits of the products available from our ICFA members.
What is Insulated Concrete Forms?
Insulated Concrete Forms (ICF) is a in-situ Modern Method of Construction (MMC) made from an insulating material. Typically available as a block, the ICF forms are stacked to create the wall and are then held in place by a raised edge – no need for mortar. The walls are usually built in stages depending on the building design, typically to storey height, before concrete is poured into a central cavity. Once the concrete sets the build continues to the next stage.
The process is practical and quick, making it ideal for trainees new to construction and reducing onsite labour and equipment requirements. It is practical to build the insulated walls of the ground-floor structure for a simple property in only a few days.
The Different Types of Insulated Concrete Forms Available
Have we convinced you that ICF could be the ideal build material for your next project? You’ll need some advice on choosing the best system. Within the UK the most commonly available systems are either expanded polystyrene (EPS) or woodcrete.
Expanded Polystyrene (EPS)
These ICF blocks are available in two formats. The first consists of EPS panels which are connected either by metal or plastic ties and delivered for assembly on site. Alternatively, the preformed moulded blocks with connectors already integrated with the panels are delivered to site for immediate construction. EPS forms are lighter than woodcrete which makes them easier to move around the site, but the wall may need temporary support put in place before the concrete is poured.
Beco Wallform
Beco Wallform components have tongues on the top and grooves on the bottom, forming a strong interlock in parallel and at right angles in a modular grid of 62.5mm. This means the designer can realise any plan layout to dimensions which are a multiple of 62.5mm. Smaller site dimensions may be cut exactly to size within the thickness of polystyrene once the concrete is cured.
Blocks: Wallform 250 – 1250mm (L) x 250mm (H) with 140mm concrete core width. Wallform 313 – 1125mm (L) x 250mm (H) with 140mm concrete core width. Wallform 375 – 1125mm (L) x 250mm (H) with 140mm concrete core. Wallform 438 – 750mm (L) x 250mm (H) with 140mm concrete core.
Also available: Lintel wallblock, firewall block, endsets and endpieces, 200 core endpiece, height adjuster unit, corbel wallblock, floor edge block, 45-degree corner blocks, 200 core wallblock, 45-degree corner blocks 200 core, curved wallblocks (also available in firewall and 200 core variants), curved transition block.
U-Value: Wallform 250 – 0.30 W/m2K. Wallform 313 – 0.18 Wm2K. Wallform 375 – 0.14 W/m2K. Wallform 438 – 0.11 W/m2K.
PolySteel
Polysteel uniquely uses steel ties to create the PolyBlok forms which makes them virtually indestructible and less likely to leak concrete during filling. The 1200 x 600 mm modular size of PolyBloks makes setting out in accordance with metric drawings much easier – especially floor levels and cill heights etc. The PolyBlok280 is ideal for above-ground dwellings, pool halls and garages without reinforcement. The PolyBlok330 can be used in basements and retaining walls with appropriate steel reinforcing bars. Furthermore, Polysteel’s BBA Certificate (Section 4.4) states that the Polysteel forms are suitable for use in basements. PolyBloks are uniquely suited for basement construction because the concrete forms a bond with the steel wire webs that stops water transmission through a wall.
Blocks: PolyBlok 280 – 1200mm (L) x 600mm (H) x 280mm (W) with a 150mm concrete core. PloyBlok 330 – 1200mm (L) x 600mm (H) x 330mm (W) with a 200mm concrete core.
U-Value: 0.23Wm2K for PolyBlok280 and PolyBlok330. U-values of 0.18 W/m2K are achieved by providing a layer of insulated plasterboard inside the PolyBlok walls.
Thermohouse
ThermoWall ICF comes in the form of a block comprising two leaves of EPS, with the inner leaf measuring 50mm and the outer leaf varying in thickness depending on the required U-value. The EPS leaves are tied together by galvanised steel inserts. These inserts not only add rigidity to the blocks, but they also add extra reinforcement, strength and crack prevention to the concrete, as well as security for the reinforcement steel which rests upon grooves in the metal bridges.
External Blocks: 250mm to 450mm (W) x 250mm (D) x 1200mm (L). Models include passive platinum wall block, passive gold wall block, standard external wall block, basement wall block,
Internal Blocks: internal loadbearing wall block, and party wall block.
Thermofloor (ICF): ThermoFloor is an EPS panel embedded with steel C-sections. These insulated panels are used to form cast in situ concrete floors and flat roofs.
U-Value: From 0.195 W/m2K to as low as 0.10 W/m2K
(Other products include Thermoroof (Structural panel) & Thermo Under-floor)
Woodcrete
Woodcrete forms typically combine natural wood materials with cement and water. This makes the blocks eco-friendly, durable and offers good thermal and acoustic insulation.
Velox
Velox is a lost shuttering system which features a composite formwork made of wood-cement boards and EPS insulation. These panels are assembled on-site and filled with concrete with no need for special propping systems to form solid, insulated walls. The wood-cement boards are carbon negative with every 1m3 reducing CO2 emissions by 700kg. They offer full use of thermal mass to keep homes cool in the summer and warm in the winter while the EPS insulation enhances energy efficiency.
Velox ICFs are suitable for sustainable construction, offering durability, soundproofing, and energy savings, making them ideal for residential and commercial projects and with flat green roofs or pitched concrete roofs. The system offers an internal load bearing walls 220mm wide, internal light weight partitions at 70mm or 100mm wide, a floor system that can span over 12m unsupported and built up to 21 storeys’ high with Velox walls and concrete floors. With Velox there are no restrictions with the ability to fix screws at any point on the board and they are ready to receive wet plaster and render direct to the board.
Blocks: WS boards, WSD boards, WS-EPS boards – with insulation, WS-EPS Plus boards – with graphite insulation
U-Value: from 0.18 W/m2K to 0.09 W/m2K
Velox (Panelox)
Panelox is a sister company to Velox. They produce a panelled ICF system which utilises the Velox building system, helping to reduce on-site build times. One of the main advantages with this system is the speed of construction, with the ability to build one storey per week including concrete placement. The system uses boards constructed from recycled woodchip alongside a patented mineralising technique that ensures boards are fireproof and protected from humidity, mould and pests. It can be used for external and internal walls, ceilings and floors, and roof structures. The system’s ease of installation and superior insulation properties make it suitable for sustainable construction projects.
Blocks: WS boards, WSD boards, WS-EPS boards – with insulation, WS-EPS Plus boards – with graphite insulation
U-Value: From 0.18 W/m2K to 0.09 W/m2K
Both Velox systems are available without insulation, with a wall thickness of 220mm, giving you the flexibility to choose your preferred insulation. The starting cost for their products is £44 per m².
Each ICF system has its unique characteristics, so we encourage developers and contractors to consult with an ICF Supplier about the specifics of their project. All ICFA members provide training courses and require that either the self-builder or their selected contractor completes this training before product delivery to the site.
Head over to our ICFA Members page where you can find contact details for each supplier.