With the current level of enthusiasm about sustainability and green construction, it’s sometimes difficult to separate the facts from the hype.
Life-cycle assessment (LCA), is an analytical tool developed to resolve these disputes. It calculates the environmental impact and related expenses incurred over the lifetime of a particular structure so that owners and developers can have an accurate, fact-based assessment of which products and technologies are the most cost-effective.
The financial portion of the analysis, sometimes called life cycle cost (LCC) analysis, considers construction cost as well as all utility, maintenance, and other expenses over the life of the building. Future costs are discounted back to the date of construction.
The environmental portion of an LCA examines all aspects of all materials used in the building over its lifespan—from extracting raw materials and processing them into construction products, the actual construction process, environmental impacts of energy usage, and disposing or recycling the building. This “cradle to grave” assessment is widely considered to be the most accurate long-term forecast of a building’s actual economic and environmental footprint.
Within the last 15 years, a number of organizations have performed life cycle assessments on ICF structures, comparing them to wood-frame, masonry, steel, and other building methods. These studies indicate ICFs outperform other building materials in nearly every region and type of construction. Their energy efficiency, disaster resistance, and recyclability make this construction method one of the greenest building technologies on the planet.
As a rule of thumb, building with the lowest construction costs require higher maintenance and higher energy inputs over the building’s lifespan. Instead of automatically selecting the low bid option, an economic LCC analysis will give owners a more accurate picture of long-term costs.
Some LCA consultants perform their analysis with a service life of 20 or 30 years, even though the average life of most building shells is actually 50 to 100 years. The PCA website states, “Such studies overstate the cost of construction materials and understate the cost of maintaining and operating the building. However, when an LCC study is done correctly, the long term cost benefit concrete provides is obvious.”
The environmental portion of the LCA is even more involved than the finances. It includes environmental impacts due to:
- Extraction of materials and fuel used for energy;
- Manufacture of building components;
- Transportation of materials and components;
- Assembly and construction;
- Operation, including energy consumption, maintenance, repair, and renovations; and Demolition, disposal, recycling, and reuse of the building at the end of its functional or useful life.
- Sometimes, they also include a building’s impact on climate change, health effects, and toxicity.
Crunching the Numbers
Obviously, a LCA involves manipulating large quantities of complex data points. The PCA website states, “There are a number of LCA tools that have been developed for general building professionals. These simplify the analysis but have a number of challenges. The BEES software tool developed by NIST (National Institute of Standards and Technology) does not account for energy performance, and looks at individual materials only; the Athena tool, developed using Canadian data does account for energy performance, and looks at building assemblies. However neither system is complete.”
SimaPro, a modeling software developed by a Dutch firm, is one popular option for complete construction and maintenance costs over the lifespan of the building. For an even more sophisticated look, LCA professionals will often perform a separate analysis of annual heating, cooling, and other occupant loads. This is frequently accomplished using a program such as DOE2.1e.
ICFs Stack Up Nicely
Studies show that very little of a building’s total environmental impact is related to construction. Rather, heating, cooling, and operating the building add up to more than 90% of a structure’s total environmental impact over its lifespan.
Concrete’s thermal mass, combined with a continuous layer of EPS insulation, saves energy over the life of a building, thus reducing overall environmental impact.
The first study to really analyze the long-term cost-efficiency of ICFs was funded by the PCA in the early years of this century. The findings were published in 2002 as Life Cycle Assessment of an Insulating Concrete Form House Compared to a Wood Frame House. The two 2,400 sq. ft. home plans were identical, other than the exterior wall system and the HVAC system, which was smaller in the ICF house. The comparison was modeled in five cities representing a range of climates (Phoenix, Miami, Washington D.C., Seattle, and Chicago).
The executive summary summarizes, “The results show that in almost all cases, for any given climate, the environmental impact in each category is greater (worse) for the wood house than for the ICF house. The largest impacts are in the form of depletion of fossil fuel reserves (categorized as damage to natural resources) and release to the air of respiratory inorganics (categorized as damage to human health). Among the construction products used in the house, wood products and copper tubing have the largest environmental load, followed by cement-based materials.”
The complete report runs 168 pages and is available free online. It should be noted that the authors of this study, Medgar L. Marceau and Martha G. VanGeem, prepared two other reports—one comparing a wood-frame house to concrete masonry and the second comparing wood to tilt-up— that same year, so it’s possible to examine how ICFs stack up to all three of these building materials.
In 2008, Marceau and VanGeem published an updated version of the ICF vs. wood-frame study, noting that the newer version “incorporates the most recent life cycle inventory (LCI) data on portland cement and portland cement concrete and the latest requirements in building energy conservation codes.” The increased stringency of the 2006 International Energy Conservation Code (IECC) made little difference, they found. The 2008 study confirmed once again that “occupant use of energy, particularly electricity and natural gas for cooling and heating, represents the largest source of negative environmental impacts,” and that over the life of the home, ICFs perform significantly better, both economically and environmentally, than the alternative.
Most recently, in 2011, yet another LCA was published by the Massachusetts Institute of Technology’s Concrete Sustainability Hub (CSH). While it compares only two cities (Chicago, representing a cold climate, and Phoenix, representing a hot, dry climate), it compares the environmental and economic impact of ICFs for commercial, multi-family, and single-family residential construction.
John Ochsendorf, co-director of CSH, authored the report. He states, “Over the past year, we have conducted LCA studies of large commercial buildings, single-family residential buildings, and multi-family residential buildings… This research provides a new level of clarity for carbon accounting, which will help to develop more quantitative approaches to green construction in the future.”
His research confirms the PCA data, that “more than 90% of the life cycle carbon emissions are due to the operation phase, with construction and end-of-life disposal accounting for less than 10% of the total emissions.” He continues, “Insulated concrete form (ICF) construction can offer operational energy savings of 20% or more compared to code compliant wood-framed buildings in a cold climate such as Chicago… This same percentage is a reasonable estimate of lifetime savings in carbon emissions associated with the use of ICFs. The energy savings can compensate for the initial carbon emissions of the concrete within a few years of operation.”
In the second half of the MIT report, Ochsendorf and his colleagues examined a hypothetical 12-story, approximately 500,000 sq. ft. rectangular office building (250ft by 165ft) recommended by the U.S. Dept of Energy. Here, concrete was compared to steel frame construction. The report states, “Particular care was taken to model the thermal characteristics and material requirements of the walls… Care was also taken to accurately model air infiltration, on the basis of leakage characteristics of individual components and whole-building leakage data published by the National Institute of Standards and Technology (NIST).”
While this study used regular cast-in-place concrete instead of ICF, the report still found that the “added thermal mass of concrete construction over steel construction provides annual energy savings in heating, cooling, and ventilation (HVAC) of 6% in Phoenix and 5% in Chicago, which can accumulate to provide carbon savings throughout the life cycle.”
As the green building movement becomes more sophisticated, it is becoming more fact- and performance-based. Life Cycle Assessment is a powerful modeling tool that provides hard data on the impact building materials have on sustainability, maintenance, and finances over the life of the structure. Based on available data, Insulated Concrete Forms are among the most desirable options.