In the Eye of the Storm: Hurricane-resistant Design
In this two-part blog, Nadja Turek and Doug Brown shed some light on designing structures to withstand devastating hurricane damage.
Once you have assessed the risks for your project’s location (part 1), it’s time to consider the building’s context and mission. As a team, discuss the dependence of the building upon or in service to the broader community during and after a hurricane. What systems (electrical, water, thermal comfort) require continuity? Can or should this building act as a “life boat” after a storm, or will it be shuttered and its function moved elsewhere?
With a strong understanding of the risks and resiliency goals, you’re prepared to evaluate design strategies.
Part 2: Design Strategies
When you are building in a hurricane zone, be sure to consider—and implement—the following recommendations in your design (when possible):
- Select the site with hazard minimization in mind.
- Raise the finished floor elevation above the storm surge line.
- Develop a water-intrusion strategy.
- Dry-floodproof: Create an air- and water-tight building envelope which may include automated or manual floodgates at openings.
- Wet-floodproof: Define areas that can and will be inundated (i.e. main level garage or warehouse where materials can be moved higher before the storm) and design them with robust, mold-resistant and easy-to-clean-and-dry materials.
- Hybrid: Incorporate both dry- and wet-floodproof elements within the same building as logic dictates.
- Reinforce the building envelope. Insulated concrete form (ICF) walls are a favorite strategy as they can withstand high winds and provide superior air- and water-tightness. As a bonus—they are also energy efficient.
- Incorporate impact-resistant windows and doors.
- Reinforce the roof and eliminate (or at least minimize) the equipment located there.
- Elevate transformers, pumps, air handlers and other critical mechanical equipment within the building.
- Draw upon regional vernacular design ideas for post-storm resiliency. In the aftermath of a hurricane when the power and air conditioning are out, day-lit buildings aligned to catch breezes through open doors and operable windows can still be inhabitable and functional.
Many of these recommendations are seemingly logical and available at low or no cost. However, when they add any amount of cost, we are often asked to justify the investment by quantifying the life-cycle cost (LCC) savings. While LCC for energy savings, for example, is well established, LCC methodology for resiliency is not. Typically, we “buy” risk reduction and avoidance, yet we lack standardized cost assumptions for damage avoided to cite in the LCC analysis.
We all share this challenge, but the industry is maturing. A good resource in the discussion of hurricane-proofing costs is the Massachusetts Institute of Technology’s Break-Even Mitigation Percentage model. While it is focused on multi-family residential buildings, it provides a good overall framework for understanding costs and risks within specific areas.
We should not forget that even with the most fortified structure, it is impossible to predict every scenario, and nothing is more powerful than Mother Nature. What we can do is make wise and informed design choices now and put good building elements into place for the day when the storm does surge.