A house that the big bad wolf can’t blow down and is more cost-effective and eco-friendly isn’t the stuff of fairy tales. But home builders should be aware of the environmental tradeoffs that may come with insulated concrete form (ICF) construction.
A year-long study from MIT found that homes built with insulated concrete-form construction were stronger and more energy efficient than traditional wood frame buildings and would have a lower carbon footprint over the life of a home.
Homes built with ICF are constructed of hollow expanded polystyrene foam blocks that interlock, much like Legos. The blocks are then filled with concrete to form a strong and airtight building.
However, some green building experts contend the environmental costs of building with concrete and synthetic foam blocks are too high.
Lloyd Alter, a green architect in Toronto, wrote on Treehugger.com that that while homes built with ICF construction may have energy efficiency advantages, “neither concrete nor expanded polystyrene foam are particularly green materials."
Alter noted that concrete has a large carbon footprint due to the energy used to make and transport it. The foam is made from hydrocarbons such as oil, which also contributes to a large carbon footprint. Alter cautioned home builders to take into account the overall environmental impact of ICF construction, not just the potential energy savings.
“An equivalent insulating value can be achieved without such massive use of carbon and hydrocarbon intense materials,” he said.
The ICF findings came out of an MIT research program funded by the Portland Cement Association and the Ready-Mix Concrete Research Foundation called the Concrete Sustainability Hub. The ongoing research will develop a model for assessing the carbon emissions of homes during a 75-year period.
Ultimately, the research will “demonstrate the potential energy savings due to the benefits of thermal mass, effective insulation, and reduced air infiltration, which are inherent in ICF homes,” said John Ochsendorf, an associate professor for MIT’s departments of architecture and civil and environmental engineering, one of the researchers on the study.
During the year of analysis, MIT researchers found that:
- The advantages of higher R-value and lower thermal bridging enables ICF homes to deliver energy savings in heating, cooling, and ventilation compared to conventional wood-frame construction.
- For residential buildings, ICF construction can offer operational energy savings of at least 20 percent compared to code-compliant wood-frame buildings in a cold climate such as Chicago.
- More than 90 percent of the life-cycle carbon emissions are due to the building’s operation phase, with construction and end-of-life disposal accounting for less than 10 percent of the total emissions.
Awareness of ICF construction is growing in the building industry. According to a market research survey by the Portland Cement Association, 36 percent of builders surveyed have used ICFs at some point in the last decade, while 6 percent of the homes built in 2007 by this same group utilized ICF construction. This represents a 60 percent increase in use since the last survey in 2003.
ICF construction can provide contributions toward points in the U.S. Green Building Council’s LEED Green Building Rating systems.
MIT will release a follow-up study in 2011 that examines the economic costs of ICF construction to provide the most comprehensive analysis of the total costs of building materials. Since HVAC energy savings directly translate to cost savings, much of the economic studies to come will build upon existing findings and highlight additional economic life-cycle attributes of building materials, Ochsendorf said.
Watch this video on ICF construction basics from Amvic:
ï»¿ï»¿ï»¿(Photos courtesy of Nudura Inc.)