Article 5
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Warming to Stay in Placeby Paul Comozzi-- Editor's Note: This article is adapted from a paper by Paul Camozzi, a former environmental consultant, now with Amvic, Inc., presented at the International Conference on Climate Change, held last summer at the University of Waterloo, Ontario, Canada.
The Oak Ridge National Laboratory in Tennessee recently embarked on a two-year study comparing the thermal performance of an insulting concrete form (ICF) system with that of traditional wood frame in typical housewall construction. While the study aims in general to establish the relative energy efficiencies of these building materials and methods, a key concern will be determining how energy-efficient design and performance results in net reductions in the carbon emissions known as "greenhouse gases."
While some dissent, most scientists agree that excessive greenhouse gas emissions -- mainly, but not exclusively, carbon dioxide, or CO2 -- are behind our present global warming trend. Although many people may think of these emissions as coming solely from factory smokestacks and vehicle exhaust pipes, statistics from Enviroment Canada (analogous to the U.S. Environmental Protection Agency) indicate that 17% of carbon emissions are generated by homes and other buildings.
Energy-efficient construction can significantly decrease these emissions. Studies by Natural Resources Canada show, for example, that over 20 years, a 2,000sf oil-heated ICF home eliminates some 150 tons of CO2, as compared with a standard wood frame home of the same size. this represents a 40% reduction in operating energy requirements over conventional constructions.
While reduced heating and cooling requirements save occupants' money and reduce the amount of fresh CO2 being produced, an ICF home makes an even great contribution to cutting green house emissions by preserving living "sinks" for surplus carbon -- our forests. To be sure, concrete construction can require the use of wood for everything from form bracing to finish moldings. On average, however, the amount is negligible. Obviously, it takes far more wood to construct a "stick-built" house of comparable size and design.
A corollary benefit stems from the fact that, typically, less than 1% waste is generated on an ICF residential construction site. In contrast, conventional wood framing methods can produce 15-20% waste, which in most cases goes to the nearest landfill. Every dumpster of miscellaneous jobsite trash means that much less valuable space at the dump. It also means more material to contribute to the creation of methane gas. This unanticipated by-product of landfills, methane gas, is becoming a major factor in global warming. As a greenhouse gas, one ton of methane gas equals 21 tons of CO2.
For anyone professing an environmental conscience, these "green" features might provide reason enough to opt for ICFs in new home construction. For those needing extra incentive, a shift from the causes of global warming to its effects may prove persuasive.
Hurricanes and tornados may be nothing new, but their recent occurrences have wrought havoc in many parts of the U.S. While scientific models point to global warming as the chief culprit, the Federal Emergency Management Agency (FEMA) has chosen not to wait for a definitive answer on what's to blame. Instead, FEMA has instituted Project Impact, a nationwide effort to transform attitudes toward natural disasters from the reactive cleanup mode to proactive damage prevention. Project Impact encourages communities to adopt construction methods that minimize catastrophic losses due to storms.
Research shows that poured reinforced concrete offers optimal protection in hurricane and tornado wind conditions. Tests done by the University of Texas Austin have unequivocally demonstrated that of all the common residential construction systems, only solid concrete walls stop a typical storm-blown projectile -- in this case, a 2x4 traveling at over 100 mph -- dead in its flight path with only cosmetic damage to the exterior of the wall. The same wooden missile flies right on through the wood-frame wall.
People in the line of fire are beginning to realize that concrete construction offers their best resort for safety in extreme weather. In the wake of Hurricane Andrew's devastation, the State of Florida upgraded building codes to require new construction to withstand 110-mph winds and include a continuous steel tie from roof to foundation. This is an ideal application for ICFs. Although wood frame construction was once the rule in the Caribbean, three destructive hurricanes in a decade have caused many builders and buyers to opt for concrete block and poured-in-place.
Whether or not these increasingly powerful natural forces stem from global warming is ultimately a moot point. The preponderance of evidence suggests that unprecedented climate change is underway. And since both probably causes and possible effects of that change relate to the construction materials and methods we choose, the time is right for marketing building systems that will help out on both fronts.
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