Exploding the myths of insulating concrete formwork construction technology

The Insulating Concrete Formwork (ICF) industry abounds with inaccurate information. Some have been passed on by members of the industry, while others represent simple misunderstandings about the technology. Most of these misstatements are made by people who simply lack the proper knowledge behind the information. The hardest part of investigating ICFs is not finding the information, but rather sorting out all the inaccurate information.

Virtually every aspect of the ICF industry is affected by incorrect information, but the most common problems involve discussions of the R-value, waterproofing, and termites and insects. R-value statements range from R-18 to R-50 +. To blow up this myth and gain a clearer understanding of this myth, you will need a firm understanding of the R-value and the difference between PERFORMANCE and TRUE R-values.

Myth 1: R value

An R value is the measure of resistance (R) of the heat flow. The heat flow can be resisted by insulating materials such as plastic foams or mineral fibers, or it can be slowed down by massive and dense materials such as thick masonry or concrete. The higher the R value, the higher the resistance and the better the insulation value.

All building materials transfer heat to some degree. Heat transfer can be measured by any of the following: 1. Conductivity (k); 2. Conductance (c); 3. Transmittance (U); 4. Resistance (R).

The ability of dense materials to retard heat flow depends on their ability to store heat and is measured by specific heat and heat capacity. (BTUs per pound per degree F; Density pounds per foot3; Heat capacity BTUs per foot3 per degree F)

When it comes to stating R-values ​​in residential construction, insulation values ​​applied to a wall or ceiling generally refer to the R-value of the insulation material being installed, not the wall or ceiling assembly. For example, when a 2×4 stud wall is insulated with R-11 block insulation, the builder indicates that the wall is R-11. This is not totally accurate and NOT TRUE as approximately 20% of the wall is not insulated at all. Wood frame and siding have an R-value, but for the sake of making insulation claims, they add very little. The actual R-value or R-value for PERFORMANCE ends between R-3 and R-9. Add to this, the fact that the wall is full of penetrations, such as electrical plugs, etc. and the fact that the wall itself is basically hollow in nature. This additional thought leads to another discussion of air leakage through the wall.

With ICF technology, the TRUE wall insulation value is that of expanded polystyrene (EPS) as EPS provides a continuous insulation plane from base to top plate. The insulation value of EPS is determined by the density and thickness of the material. Some ICF systems have EPS of different thickness (waffle and post and beam systems) that typically average the thickness of the foam. In my opinion, this is not an accurate measurement, as a bucket with a hole in the bottom does not carry as much water as a solid bucket with a hole in the top. Most ICFs use EPS foam that has a density of approximately 1.5 pounds pcf to 2.0 pounds pcf. Insulation values ​​differ only slightly in that range and, based on the test lab, provide R-values ​​between R-4 and R-4.5 per inch of EPS thickness.

The claim that ICF walls are an R-50 started a few years ago after the Insulating Concrete Formwork Association (ICFA) and several members commissioned CTL Laboratories in Chicago to perform some R-value testing and analysis. The report basically said that, depending on the climate zone, the PERFORMANCE R-values ​​for ICF technology are as high as an R-52 when COMPARED to typical wood frame and wood slat construction. For the comparison to be correct, one must ensure that the comparison is made vs. the alternative to ICF in the particular project. On average, the performance R-value is much lower than the declared R-50. Consumer research should be done to clarify the actual project comparison. In short, ICF WILL WORK at an R-50, but that statement is not accurate when it comes to insulation value.

For more information on insulation values, green building, and low-energy building, visit these websites for research: Energy Star Program, Concrete Homes. Do a Google search to find many others. It is worth noting that there are many options for researching on the internet and that I do not own or control any of the suggested research links listed in this article.

Myth 2: waterproofing

Yes, concrete constructions below grade must always be waterproofed and this includes ICF technology. Three options include: dimpled membrane, peel and stick membrane, and spray products. In some US jurisdictions, a combination of dimpled membrane and peel and adhesive membrane or spray or roll application products must be used to comply with local building codes. It is best to check with local building code officials and your local ICF supplier to make sure you meet the minimum code requirements and use only products that are EPS compliant.

Myth 3: termites and insects

Under the ICFA, the International Residential Code has provisions in the IRC to allow foam to be used below ground level. The IRC stipulates that in addition to chemical soil treatment, foam may be used below grade on the outside of the wall if one of the following requirements is met:

1. All interior partition walls and roof trusses are constructed of a non-combustible material, such as steel posts or pressure-treated lumber.
2. An approved method is used to protect the foam plastic and the frame.

Polyguard Underseal (TM) XT Waterproofing Membranes has an evaluation report showing that they are an approved method of protecting foam from termites below ground level. Visit the Polyguard website for additional information on Polyguard. Tip, you may want to install an aluminum termination bar along the top edge (aka: termite stop and ant stop). One benefit, in addition to stopping bugs, is that the finish bar helps to scratch the stucco, etc. On the foam you will need to protect the exposed foam area. Also, don’t run your siding to grade. This is just another shortcut for ants, termites, and other insects to get up the wall and start nesting behind your siding.

Remember, these insects do not eat foam, but they can go through it, especially in search of food. Eliminate the food source and eliminate the problem. Wood products can be totally replaced in your new home. There is no longer any reason to use wood products in areas of the US with high termite infestation. Consider steel framing, AZEK trim boards, and V-Buck for your next project and get the lumber out there! Although many additional myths exist and continue to flourish, it is important that you remain diligent in gathering information. As you search for additional information, be sure to work with those who have the heart of a teacher. Look for those who have a passion for the industry and who understand and can explain the issues.