Extreme Weather: Impact on Where, How We Build
- Jun 21, 2010
New York–Worldwide, greenhouse gas emissions caused by human activities increased 26 percent from 1990 to 2005, according to the U.S. Environmental Protection Agency. Because buildings contribute to nearly half of this amount, much emphasis has been placed over the last several years on greening this sector.
Changing weather patterns is just one result of this increase in greenhouse gas emissions; the EPA reports that temperatures have increased in the past decade—as have the frequency of heat waves—drought conditions in the U.S. have increased between 30 and 60 percent from 2001 to 2009, and precipitation has increased about 6 percent per century. Meanwhile, heavy precipitation has increased, with eight of the top 10 years for extreme one-day precipitation occurring since 1990. Moreover, in the past 20 years, the intensity of tropical storms has risen, with six of the top 10 most active hurricane seasons occurring since the mid-1990s.
Extreme weather, causing larger storms, stronger winds and more flooding than ever before, is certainly here, and unpredictable patterns are happening in areas that previously did not experience them, thus making weather planning for construction that much more difficult. With these weather changes on the rise, new techniques are going to need to be considered during a building’s planning stages. Some cities, such as New York, are in the midst of developing solar and flood maps, which could show not only which buildings are best suited for solar power, but also which areas appear to be most vulnerable to floods—an idea that could help during the weather planning stages.
Generally speaking, “a project schedule should include sufficient planning to accommodate the same amount of adverse weather as anticipated in the rolling average of adverse weather,” says Chris Carson, PSP, CCM, PMP, corporate director of project controls at Alpha Corporation, a Dulles, Va.-based consulting firm offering engineering and management services for project or program development and delivery. “This is the best that can be done to provide for anticipation of adverse weather, short of serious statistical analysis, which does not provide a reasonable return on the time and costs.”
In a typical situation, weather planning—the organizational phase before scheduling—in construction projects is typically based on a rolling three- to five-year average of historical adverse weather—weather that forces a shutdown of at least 50 percent of the productivity on a project, according to Carson. Sometimes this can be impacted by a rarity; in 2002, for example, the East Coast had its worst historical 20-year average adverse annual weather. “The weather planning was insufficient for the actual weather,” recalls Carson. As a result, Alpha Corp. has since incorporated a higher level of impact in its planning stages.
Multifamily developments, however, are built with a slightly different philosophy than other types of projects, according to Carson. “These projects are generally funded with an anticipation of seeing rent or sale income very close to the planned completion, based on the pro forma, so the attitude in multifamily is oriented toward mitigating any lost time rather than extending the completion date, no matter what the delay type is or who is responsible. “
Because of the difficulty in planning all weird weather events, however, some new techniques should be implemented into buildings. Most important to a building is, of course, its location. “It’s important that things are built for where they are instead of where [we] wish they were,” points out David Borchardt, P.E., LEED AP, Chief Sustainability Officer, Tower Companies, who will be teaching a course, “Sustainable Construction” this fall at Georgetown University School of Continuing Studies.
Unfortunately, location is no longer a builder’s only predictor for climate. No matter where it is, a building needs to be more resilient to storms and other extreme weather. Buildings will need to incorporate more robust materials—including those that are more resilient to high winds and rainfall—which will need to be “certified in a way that makes them live up to advertising,” Borchardt notes, particularly as insurance rates will be greatly affected by the materials used. “What will drive this is the insurance industry and the sale of properties. [If] someone is building and it’s not robust enough to meet insurance requirements, it won’t sell,” he points out.
Wood-frame multifamily buildings, for example, should incorporate clips to hold down roofs and windows that resist water infiltration, while gypsum board can withstand higher levels of moisture. Borchardt also recommends using structural insulated panels (SIPs), high-performance building panels of rigid foam plastic insulation between two skins of oriented strand board, which can be used in floors, walls and roofs for residential and light commercial buildings.
In addition to the materials used, construction techniques for extreme, or unpredictable, weather conditions include “project timing, to avoid the worst weather risks, fast-track construction to complete before adverse weather seasons, temporary protection efforts such as temporary roofs or enclosures, higher productivity construction techniques and increased pre-assembly to allow shorter time on site,” says Carson.
While LEED (Leadership in Energy and Environmental Design) does not consider this idea of extreme weather specifically in its standards, there are a number of criteria from the standard that could, and should, be considered when building with climate change, and its resulting conditions, in mind. These include, among others:
• Integrated project planning (taking advantage of the team to discuss weather risks),
• Management for durability (higher-quality process will mitigate impacts from adverse weather, especially in the moisture control and environmental tightness areas),
• Innovative design (could provide good site design for drainage to minimize effects from rain or snow during construction as well as elevations above floodplain),
• Erosion controls and exterior water (control of runoff is an integral part of LEED, and important to prevent sites from becoming impassable and affecting work, and grading the site early to move surface water away from the buildings),
• Maintaining trees/reducing local heat island effects (the less stripping and grubbing, the better the site will withstand precipitation dumped on the site),
• Surface water management (includes permeable surfaces lowering the damage from precipitation),
• Managing roof runoff (if installed early, can lower damage from precipitation),
• High energy performance (tighter buildings can help keep precipitation from entering the under-construction facilities).