By Scott Kriner, Green Metal Consulting
We are now officially in the 2016 hurricane season. We already had a named Atlantic hurricane near the Azores in January! Colorado State University (CSU) is predicting near average activity in the Atlantic. CSU predicts a total of 12 named storms, and six hurricanes (three at Category 3 level or higher).
So as residents in the high-wind areas of our country think about the supply of plywood, generators, and evacuation routes, the dialogue also turns to how to make our buildings stronger against high winds. In this year’s proposed changes to the International Building Code there were comments from the American Society of Civil Engineers to increase a roof’s ability to withstand even higher wind pressures, especially in high-wind regions.
The dialogue on resilient design of buildings from major storms like hurricanes rages on. The National Institute of Building Science (NIBS) is taking on a leadership role in this area. In fact, NIBS recently moderated a White House Conference on Resilient Building Codes. The American Institute of Architects has also announced their support of resilient design strategies. The four “R”s of Resilience in the wake of natural or man-made threats are 1) Robustness, 2) Resourcefulness, 3) Rapid Recovery, and 4) Redundancy. The focus is not just on building design but also design of communities to withstand natural hazards as well as man-caused threats.
Some programs have been creating standards for making our buildings and homes more resilient to damage from hurricanes and high-wind events. One such program was developed by the Insurance Institute for Business and Home Safety (IBHS) – the research/testing arm of the insurance industry. Their Fortified Home™ program is designed to help strengthen new and existing homes through system-specific building upgrades to exceed the minimum code requirements. Three levels of strength are available depending on the budget, the level of required protection and resilience goals.
Within the IBHS Fortified Home program for High-Wind events the guidelines cover:
- Sealed roof deck
- Standards for roof deck and roof covering
- High-wind-rated roof cover
- Braced end walls
- Roof-to-wall connections
- Wall-to-floor connections
- Floor-to-foundation connections
- High-wind-rated roof-mounted vents
- Protecting gable end vents against water intrusion
The roofing industry is well aware that some of the highest levels of wind uplift pressure take place at corners and the perimeter edges of roof systems. The construction industry can either strengthen those areas of a roof or change the geometry of the roof. Neither are slam dunks in lowering the risk of roof failure in hurricane-force winds.
A prefabricated home builder in North Carolina has taken the change in geometry to the extreme with excellent results. Deltec Homes, from Asheville, NC, prides themselves on the fact that since their founding in 1968 and after 5,000 homes built in hurricane-prone areas since then, they have not lost a home to wind events. They attribute their success to the unique design and shape of the home, the quality of their materials, and engineering methods. The design of the relatively low-sloped roof is based on a circular plan so as not to have any corners, stark edges, or sharp angled areas. Where a corner joint is unavoidable it is beveled to provide a smooth surface. Their website shows metal roofing on some buildings, which many in the metal construction industry would support for the inherent strength, aesthetics and design flexibility.
This extraordinary success is also attributed to the use of pre-fabricated structural components, wall panels, and floor joists that are all assembled into a house at the site. The houses are also designed for net zero energy standards as well. Many of their units use rooftop photovoltaic modules. The wall panel assemblies have insulation already sprayed into them and house wrap is attached to the panels before they are installed.
Whether we consider a building or a home as being fortified, strengthened, or resilient, the future of the built environment will likely change to respond to more severe and more frequent storms in areas of our country. Using metal on the building envelope of buildings can offer many attractive attributes such as strength, water resistance, corrosion resistance, ductility and toughness. Using metal with the proper design can create a long-term solution to fight off Mother Nature when she bears down on our building stock with incredible force. It may be based on “circular” logic.