The Thermal Properties and Benefits of Building with Insulative Concrete Foams

The Thermal Properties and Benefits of Building with Insulative Concrete Foams

June 15, 2021

Introduction

Climate change is one of the most troubling global concerns that world leaders have been attempting to tackle since the start of the 21st century. As public awareness of environmental issues continues to rise, it is also having a more pronounced influence on consumer choice. The global effort to live in a more sustainable fashion is widespread and is demonstrated through a surge in the production and sale of green technology throughout numerous global markets.

One example of an industry that is being heavily influenced by a consumer push towards sustainability is the construction and building sector. Manufacturers in this market are attempting to make more environmentally friendly products and produce them using sustainable and green techniques. This heightened focus on a product’s energy saving abilities has led to a spike in the popularity of insulative concrete foams (ICFs) as the material of choice for developing new buildings. The newly proclaimed appreciation and increase in demand for ICF has led to more global production of the material as it is being in many countries for a variety of commercial projects including the construction of apartments, hotels, retail, and movie theatre buildings.

ICF R-value

Insulative concrete foams offer a stronger, insulative, and sustainable alternative to traditional wood-framed buildings that has both long term economic and ecological benefits in terms of reducing cost and energy demands. The secret to their thermal powers is due to the combination of reduced thermal conduction and convection as well as having a high thermal mass. This winning combo not only lowers the building’s energy use but also improves the comfort inside by blocking drafts and offering superior thermal absorption. Most of the desired thermal properties displayed by ICF are indicated by their high R-value. The “r” in R-value stands for resistance with materials displaying a higher R-value having better resistance to heat flow compared to materials with a low R-value. EPS foam, from which ICF is made, is one of the top insulating materials on the market. ICFs typically contain 5 inches of EPS insulation with testing insulative values ranging between R-22 and R-26.

EPS insulation also possesses optimal sound absorbing qualities. They only allow roughly 12.5% – 25% as much sound to pass through them compared to wooden walls. In the eyes of a business owner, this key component of ICF makes it extremely desirable especially if the location of the building is in a loud city street or a downtown metropolis. Additionally, buildings and homes constructed using these materials offer a level of safety very few building systems can match. They average at being 10x’s stronger than a standard framed structure and several times stronger than CMU ‘cinder block’ construction.

The ICF – EPS combo is highly favored by the military and law enforcement due to it being a blast and ballistic resistant. EPS foam is unique in that it will not burn when exposed to high heat but will melt instead. Despite melting when exposed to these conditions, it will not contribute any fuel to a fire and has self-extinguishing properties due to a flame retardant that is added to EPS foam by all of the leading ICF manufacturers.

ICF-insulation

Figure 1: Close up of ICF insulation with metal reinforcement.

R-values are key for measuring the thermal resistance of a material, however, when trying to assess the energy performance of a building, they lack the level of detail required to determine the actual heat transferring properties to be the only considered value. The main factors that are more representative of the energy performance of a building include thermal conduction, convection, radiation, and mass.

Heat-exchange

Figure 2: Heat exchange mechanisms including thermal conduction, radiation and convection.

Thermal conductivity of ICF

The thermal conductivity of material directly relates to its ability to effectively facilitate the transfer of heat through it. Thermal conductivity is also widely referred to as thermal conduction, which is the heat transfer through a material by direct contact of one molecule to another.  Conduction is the only factor that an R-value directly measures. Wood framed insulation has an R-value accessed only in terms of the highest rated component of the wall insulation itself. This value can be extremely misleading as most builders will generally refer to a building as having R-13 or R-21 walls while neglecting to disclose that these values are the only representative of the highest and most thermally insulative material in the entire structure.

A wood frame is made up of several components that have a variety of different R-values making the authentic insulation value of the building significantly lower, and in some cases, only half of the advertised value. On the other hand, ICF walls consist of a center cavity designed to house concrete between two layers of EPS insulative foam which provides two largely continuous layers of insulation rated at R-22 or higher.

EPS-insulative-foam

Figure 3: EPS insulative foam stacks

Thermal convection and ICF

Despite the focus of insulative materials generally being centered around thermal conduction, it is thermal convection that contributes to the majority of the heat loss occurring in a building. Convection is characterized by heat transfer that occurs through the movement of currents within a fluid or gas. When referring to convection within a building, it is generally the air moving between the inside and the outside of a building or “air filtration” that characterizes the quality of an insulative material.

A common measurement used within the construction industry for describing air filtration is “air changes per hour” at a blower-door induced pressure differential of 50 pascals (ACH50). U.S. energy star standards for new homes require less than 4-7 ACH50. These standards are extremely relaxed compared to the stricter regulations imposed in Canada, which has an R-2000 standard of 1.5 ACH50, and Sweden which requires 0.5 ACH50 or less. In terms of measuring insulative quality, the higher the ACH50 value, the more inside and outside air filtration is occurring.

In a standard wood framed building, convection is experienced as drafts and is often the biggest contributor to energy loss in a building. Air infiltration can account for upwards of 40% of the total energy loss as air frequently leaks through the numerous cracks and joints between the ‘matchsticks’ that make up a wood building shell. A typical newly constructed wood home will have an ACH50 between 1.75 and 3, however, after a couple of years, this number can skyrocket to values between 5 and 10 as the wood shrinks and deteriorates. Older wooden homes lack almost any insulation and commonly have ACH50 values averaging between 10 and 20.

ICF buildings far surpass a wood framed structure in terms of blocking airflow and maintaining a stable indoor temperature regardless of the external weather or climate. Most ICF buildings display an ACH50 of 0.5-2.5 or less, with these values being heavily dependent on the roof type and sealing material. This restrictive airflow is beneficial in terms of regulating temperature, however, adequate air exchange must be maintained in these airtight buildings through the use of mechanical ventilation. This type of moderated airflow can be combined with heat/energy recovery units or ground heat exchangers for additional savings.

Thermal radiation and ICF

Thermal radiation is another important regulator of energy use in a building and one that many neglect to consider when selecting a material to use when building a structure. Thermal radiation is characterized by heat transfer through electromagnetic waves which in terms of a building come mainly from UV radiation emitted by the sun. The impact this method of heat transfer can have on the energy exchange that occurs within a building is highly dependent on factors such as site location and the prevailing climate in that region. Passive solar building designs can help optimize a building’s absorption and reflection capabilities through utilizing solar orientation, placement of windows, and selecting ideal shading elements such as choice of finishes and incorporating thermal mass.

Passive-house-design

Figure 4: Passive house design components extending beyond ICF insulation.

The thermal mass of a material refers to its capacity to store heat. Concrete and adobe bricks have a high thermal mass and act like a battery that stores heat to be released when the surrounding temperature drops. ICF that has a concrete exterior can store heat during the heat of the day and then release it inside at night maintaining a comfortable temperature while using almost zero energy. In temperate climates, the concrete performs a contrasting role involving passive solar design by letting the strong winter sun warm the high thermal mass walls and floors on the inside and outside of the building. Wood frames have almost no thermal mass, therefore, they offer none of these energy saving benefits. High thermal mass construction can be easily incorporated into ICF walls and floors which will lower the demand for active heating and cooling systems by maintaining a stable surrounding temperature for a longer period.

Reusability of ICF

It is very evident by examining the thermal properties of ICF buildings that they can save more energy and reduce air filtration compared to a standard wood home, but their benefits extend even further beyond the physical properties of the material. Using concrete instead of wood for construction can save a considerable number of trees because the entire wood frame is eliminated. Many concrete contains recycled components by using supplementary materials such as fly ash or slag to replace a portion of the cement aggregate. Older crushed cement can also be recycled to reduce the need for virgin aggregates and most steel reinforcements used during the construction process also have the potential to be recycled.

Concrete-mixture

Figure 5: Concrete mixture containing larger aggregates.

ICF buildings are a clear champion among construction materials as they offer better economic and environmental benefits compared to standard wood framed buildings. Although the initial construction cost is roughly 3-5% higher for building with ICF materials compared to classic wood, the cost of maintenance and living is significantly lower. Insurance costs are generally cheaper for ICF buildings due to their increased strength and fire resistance. Building owners will end up saying roughly 20% more on energy costs by building with ICF compared to wood.

Conclusion

Assuming a 100-year service life of a building, a single ICF home has the potential to save roughly 110 tons of CO2 which more than offsets the CO2 associated with the production of the cement used to make the concrete and can contribute to a company’s efforts to become carbon neutral or carbon negative. At a time when climate change is at the forefront of everyone’s mind, it is more important than ever to ensure that we are collectively working towards minimizing our carbon footprint. One way we can achieve this goal is by replacing outdated building materials such as wood with modern insulative concrete foams enabling both homeowners and larger building developers to do their part in mediating negative environmental impacts and reducing CO2 emission.

Author: Kallista Wilson | Junior Technical Writer | Thermtest

References

Does A Brick Home Need Insulation? | Brick Siding. (2020, March 20). Modern Design. https://gambrick.com/does-a-brick-home-need-insulation/

Insulated Concrete Forms—Energy Performance and R-Values. (n.d.). Insulated Concrete Forms ICFs by Quad-Lock. Retrieved May 26, 2021, from https://www.quadlock.com/insulated-concrete-forms/ICF_energy_performance.htm

Insulating Concrete Forms (ICFs). (n.d.). Retrieved May 26, 2021, from https://www.cement.org/cement-concrete/paving/buildings-structures/concrete-homes/building-systems-for-every-need/insulating-concrete-forms-(ICFs)

Jul 14, Resistance, 2020 | Disaster, Efficiency, E., Stories, F., Costs, I. C. F., & ICFs?, W. (n.d.). Benefits of Living in an ICF Home | ICF Builder Magazine. Retrieved May 26, 2021, from https://www.icfmag.com/2020/07/benefits-of-living-in-an-icf-home/

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