| Insulating Concrete Forms, also known as ICF | | | | in the market around the US. I always get asked the |
| construction, is a concrete building system that | | | | question "Which one is the best?" The answer I |
| offers superior strength, energy efficiency, durability | | | | always give is "Which is better, a Ford or a Chevy?" |
| and comfort compared to traditional construction | | | | Depending on who is asking, I have the following |
| methods. Although it has been predominantly used in | | | | responses: |
| the residential market during the past decade, | | | | Homeowner: It shouldn't matter to you. From a user's |
| commercial applications are rapidly increasing. | | | | perspective, all ICF brands perform dramatically |
| There are several other concrete home building | | | | better than frame construction under every |
| systems, including masonry, reusable forms and | | | | circumstance. The differences between brands will |
| pre-cast products. This article focuses on ICF | | | | not be noticeable to you. You should perform |
| technology and not on any specific manufacturer in | | | | standard due diligence and locate the best contractor |
| the ICF industry. | | | | and let the contractor use the product that he and |
| ICF construction technology is not smoke and mirrors. | | | | his crew is most comfortable using. |
| It is a very proven product in a new package. Simply | | | | Contractor: Here the differences are the greatest |
| put, it is a reinforced concrete wall identical to the | | | | and affect the type and amount of labor required for |
| ones that have been designed for years as | | | | installation and also the waste factor. Some brands |
| basements, foundations and retaining walls. The | | | | require more on-site labor, others have a lower |
| advantage is that the forming system is very | | | | material and/or shipping cost. Others are |
| lightweight, has high insulation properties and does | | | | pre-assembled to minimize on-site labor. Some forms |
| not require removal. The finished wall generally | | | | have waste percentages approaching 10%, while |
| incorporates integral attachment points for interior | | | | others are closer to 1%. It really depends on personal |
| and exterior finishes. | | | | preference and experience of the construction crew. |
| With an ICF wall, the forms are stacked, the walls | | | | Architect: Cavity configuration affects the structural |
| are braced and aligned and the concrete is placed in | | | | performance slightly, but all ICF brands have |
| the stay-in-place form. The wall is simply a monolithic | | | | load-bearing and shear strength capacities far |
| concrete core (just like any other concrete wall), | | | | exceeding frame walls (up to 600% greater in some |
| with two continuous insulation layers. The faces (AKA | | | | cases). As a designer, the biggest concern is the web |
| flange) of the ties function as the furring strips for | | | | tie face size and web tie spacing. (Example, vertical |
| attaching interior and exterior finishes. | | | | lap siding may require additional furring if the tie face |
| The initial idea for insulated block construction has | | | | is vertically oriented and has a wide spacing). It is |
| been around for over 50 years. In the 70's, | | | | worth noting that the placement of windows, doors |
| polystyrene foam was introduced. NAHB (National | | | | and T-walls can be affected by web tie spacing. |
| Association of Home Builders) performs an annual | | | | Typically, flat wall ICF products with closer web tie |
| survey of residential builders across the US. According | | | | spacing require significantly less attention to these |
| to their research, the market has exploded during the | | | | details. |
| past 5 years. The ICFA (Insulating Concrete Forms | | | | I suggest contacting the Insulating Concrete Forms |
| Association at reported that 16 percent of all new | | | | Association via the internet to obtain a list of primary |
| custom home starts in 2004 used ICF technology | | | | members. These are some of the largest and best |
| and the industry is growing by over 30% per year. | | | | established companies. Like most any construction |
| Conceptually, ICF technology is rather simple. They all | | | | product you specify, whether it is plumbing, lumber, |
| use the same basic components including a face shell | | | | or windows, it is the local people providing the |
| of expanded polystyrene foam, a core of reinforced | | | | support and service that always make the biggest |
| concrete and a plastic form tie that supports the | | | | difference. Other valuable sources of reliable and |
| face during concrete placement. The foam panels are | | | | non-biased information include: It is worth noting that |
| typically fully reversible, 2.5" thick by 16" tall by 48" in | | | | there are many other excellent resources available |
| length. The plastic ties are typically 6" on center | | | | via the internet and that I don't own or control any |
| which provides incredible stability during concrete | | | | of the websites listed in this article. |
| placement. The ties are embedded ½" inside | | | | There are three interior core configurations of ICF's. |
| the foam panel and their position is marked on the | | | | Flat wall is a simple vertical section of uniform |
| foam panel so installers can easily find them. The | | | | thickness and is the easiest to engineer and install. |
| foam provides an R-22 continuous insulation plane | | | | Waffle grid has vertical and horizontal cores - |
| from the footing to the top plate. | | | | alignment of cores must be maintained by installers, |
| The concrete in an ICF wall is nothing special. Design | | | | but uses about 25% less concrete than flat wall. The |
| specifications are typical of conventional foundation | | | | thin web section is about 2" to 3" thick. Screen grid |
| requirements. The one minor difference is the | | | | has same alignment requirements of waffle grid and |
| aggregate size. It is typically 3/8" pea gravel to allow | | | | utilizes a field installed spline between blocks for finish |
| for easy and smooth pumping of the concrete, | | | | attachment. All three types are included in the |
| especially for above grade applications. | | | | Prescriptive Method for ICF Wall Design and the |
| Concrete placed inside an ICF actually achieves much | | | | International Residential Code (IRC 2006) and |
| higher than normal and specified strength. This is due | | | | concrete walls are typically all designed and |
| to the ideal curing conditions, stable temperature and | | | | engineered according the ACI 318. However, the |
| slow moisture loss rates inside the expanded | | | | newest engineering code standard, ACI 560, will no |
| polystyrene panels. | | | | longer provide engineering data for waffle or screen |
| There are currently over 70 manufacturers of ICF's | | | | grid ICF products. |