Insulating concrete forms (ICFs) present an innovative solution to the growing demand for environmentally-friendly construction materials.
The constant hike in energy prices and the demand for environmental compliance play an important role in the construction industry. To remain competitive and one step ahead of competitors, industry professionals are constantly striving to introduce and implement innovative ideas and concepts to the market. As the demand for more sustainable working and living spaces skyrockets, so does the need for construction technologies that can streamline the building process, reduce costs and maintain quality, according to www.sabmagazine.com.
Insulating concrete forms (ICFs) present an innovative solution to the growing demand for environmentally-friendly construction materials, according to the United States Portland Cement Association (PCA). Made from cast-in-place concrete walls that are sandwiched between two layers of insulation material, these systems are strong and energy-efficient. Internationally it is regarded as a viable, beneficial alternative to conventional construction methods, according to www.sabmagazine.com. As such, construction professionals, property owners, design specialists and contractors are opting for this construction method.
Common applications for this construction method include low-rise buildings, with property uses ranging from residential to commercial and industrial. Traditional finishes are applied to interior and exterior faces, so the buildings look similar to typical constructions, although the walls are usually thicker.
Building with ICFs offers many sustainable benefits, according to www.sabmagazine.com. These include:
- High thermal resistance and air tightness. This can lead to 50%-70% energy savings due to lower heating and cooling costs.
- Most ICF products are made from non-toxic materials and do not emit chlorofluorocarbon (CFC) or hydro-chlorofluorocarbon (HCFC). This contributes to healthier living and working environments.
- It is often made from recycled materials.
- The material has a fire resistance rating up to four hours.
- ICFs have superior impact protection and can withstand intense wind speeds.
According to the PCA, owners, contractors and builders benefit from ICFs.
Owners benefit from:
- strong walls;
- disaster resistance and safety;
- energy-efficiency and cost savings;
- protection against mould, rot, mildew and insects; and
- lower noise transmission (sound blocking).
Contractors and builders benefit from:
- fast, easy construction;
- the material’s flexibility;
- the fact that the material is lightweight and can be shipped and erected with little fuss; and
- it complies with international green building codes.
ICF systems can vary in their design, according to the PCA:
- Flat systems yield a continuous concrete thickness that is similar to a conventionally-poured wall.
- Walls produced by grid systems have a waffle pattern where the concrete is thicker at some points than others.
- Post and beam systems have discrete horizontal and vertical concrete columns that are completely encapsulated in foam insulation.
The two insulating faces are separated by a connector or web. Expanded polystyrene (EPS) is most often used as a connector; extruded polystyrene (XPS), which is stronger but more costly, can also be use. A handful of products are made from recycled foam or wood fibre. The salvaged material is formed into blocks with cement, making units ideal for the direct application of plaster finishes.
The ties that bind
The ties that interconnect the two layers of insulated forming material can be plastic, metal or additional projections of the insulation. There are advantages to each type of material, according to the PCA, but one current trend incorporates hinges into the ties. This allows pre-assembled forms to fold flat for easy, less costly shipping.
The joints between individual forms can consist of interlocking teeth or a tongue-and-groove configuration that is moulded into the forming material, or simple butt-jointed seams. According to the PCA, many manufacturers have developed units with universal interlocks that allow the forms to stack – whether the form is flipped one way or the other. “These reversible forms save time during placement and prevent improper alignment. Special units for corners, floors and roof assemblies round out the product lines, and improve the engineering of the system and energy-efficiency of the final construction,” stated the association.
Block and stack
Block sizes are typically in the order of 40cm high and 120cm long. The cavities are mostly 15cm to 18cm wide, but can be larger or smaller as needed. The foam faces can also vary, but a 2,5cm to 20cm, to 5cm to 10cm, thickness is a usual range. So a 20cm cavity with a 5cm foam face on either side would lead to a 31cm formed wall. More recent systems offer thicker foam layers to enhance performance.
After finishes are applied inside and out, typical final wall thickness is greater than 2,5cm. This means that the depth of window and door surrounds have to be wider than traditional frame construction, with resulting deep window sills.
Form follows function
ICF systems are installed in a masonry-like manner. Builders usually start at the corners and place a layer at a time to build the wall. During assembly, units – particularly these that form a waffle or post-and-beam concrete wall profile – must be glued together or taped at the joints. Most modern systems feature uniform cavities that improve the concrete’s flow ability and reduce the need for adhesives during stacking. The end-result is flat concrete walls of consistent thickness.
Concrete is pumped into the forms once the forms are in place and braced and the required reinforcement is installed. Even with the bracing, forms need to be filled at an appropriate rate to prevent misalignment and blowouts. “Product advancements and improved construction techniques have greatly reduced the potential for form failure,” stated the PCA.
Wall strength is maintained by reinforcement in both directions. Openings for doors and windows require bucks to surround the opening, contain the fresh concrete during placement, and provide suitable material for fastening window or door frames.
Block-outs are needed when bearing pockets are required for floor or roof items. ICF systems are compatible with concrete floors, as well as wood or steel floor joists. In smaller buildings, ledger assemblies for floor framing attachment mounted to the side of the formwork are common. In larger or commercial buildings steel-weld or bolt plates can be pre-installed in the formwork, so that they become embedded in the fresh concrete.
Finishes are usually attached via the flat ends of metal or plastic ties that are embedded in the forming material. Finishes can alternately be lined with furring strips. Almost any type of finish can be used with these systems. Wallboard remains the most common interior finish and is the most typical means of meeting regulations for fire barriers over plastic foams surrounding living spaces. With the building envelope, cement plasters are applied over ICFs in a manner similar to other sheathed systems.
ICFs help to reduce energy-to-heat and cool buildings. Some estimates place the savings at 20% or more. The R-value for a typical ICF is about 20. The walls can often have high air tightness –10% to 30% better than traditional wood-frame windows, doors and roofs. “As a result, assuming a 100-year service life, one single-family ICF home has the potential to save about 110 tons of CO2 compared to a traditional wood-frame home. This more than offsets the CO2 associated with the production of the cement used to make the concrete,” stated the PCA.
Thermal mass is one of the reasons why ICFs work so well to maintain a consistent temperature; insulation is the other. This saves quite a bit of energy associated with heating and cooling, which not only saves money, but also provides a more comfortable interior.
The recycle route
ICF systems can also include recycled materials. Concrete can be made using supplementary cementing materials like fly-ash or slag to replace a portion of the cement. Aggregate can be recycled (crushed concrete) to reduce the need for virgin aggregate. Most steel for reinforcement is recycled. Some polystyrenes are also recycled.
From a sustainability viewpoint, the reduced operating energy, reduction of CO2, long service life, and use of local and recycled materials make ICF construction environmentally beneficial.
Full acknowledgement and thanks are given to www.sabmagazine.com and the US Portland Cement Association for providing the information to write this article.