Case Study: Lone Survivor, Mexico Beach, Florida

Photo: Johnny Milano/The New York Times/Redux

In 2018, Hurricane Michael—a Category 4 hurricane with sustained winds of between 130–156 miles per hour (mph)—tore through Mexico Beach, Florida. In what has now become an iconic image, a nearly undamaged house on stilts is shown surrounded by devastation and flattened properties.

The house was built to specifications that exceeded local codes: It was built to withstand winds of up to 250 mph.³ The home’s base consists of 12-inch square precast, pre-stressed concrete piles. Precast concrete beams extend upward from the base, supporting the interior and exterior walls for fortification from a coastal surge.

Each of the building’s 6-inch-thick concrete exterior walls was created from insulated concrete forms (ICFs) in a continuous insulation system laced with vertical and horizontal steel rebar. This method allowed siding to be anchored directly to the core of the structure, increasing the integrity overall. Concrete also bolstered the corners of the home, and space underneath the roof was minimized to prevent wind uplift.

In an interview for The New York Times, former Miami-Dade building chief Charlie Danger maintains, “‘It pays to rebuild structures that withstand something like that. You minimize loss of life—and the loss of infrastructure. If you lose the infrastructure, you lose everything.’”⁴

Constructing a building reinforced to this extent proved to be marginally more expensive than comparable buildings with a payback of fewer than four years with energy savings. The materials used for construction afforded the homeowners reduced insurance cost, a quieter structure, faster construction, and lower energy bills, all of which will be discussed in greater detail in upcoming sections.

First-Cost Comparison

Senior Living Facility: ICFs versus Wood Frame

ICFs can easily be compared to wood-frame construction to assess long-term cost savings. One example is a senior living facility in Oconomowoc, Wisconsin:

• Total size of wood-frame construction = 176,444 square feet
• Cost of wood framing including the exterior insulation = $4.32 million or $24.48 per square foot
  • The codes have stepped up to increase insulation requirements on the exterior of multifamily buildings, which also drives up the costs.
• Cost of wood framing minus the exterior walls = $3.4 million or $19.27 per square foot
  • This is the same project without exterior walls. Wood is only used on the interior (for example, trusses, floor joists, interior walls).
• Cost of ICF exterior walls = $950,000 or $5.38 per square foot
• Total for wood frame = $4.32 million
• Total for ICFs plus wood frame interior = $4.35 million

Pros of ICFs During Construction

ICFs offer the following benefits for projects like the senior living facility discussed above.

• Ability to pour stair towers and elevators shafts concurrent with structure, also making both more soundproof. For example, a mason does not have to come in to run a CMU shaft prior to the walls going up.
• Eliminate exterior vapor barrier.
• Continuous R-22 or greater continuous insulation with the added bonus of concrete thermal mass.
• Can pour in winter conditions (down to 15 degrees Fahrenheit because both sides of the wall are insulated; the contractor simply insulates the top of the wall).
• Structural integrity of the wall allows for numerous possibilities, including hanging balconies, masonry tower, or trash chute tie-offs, skip hoist tie-offs, etc.
• Improves sound transfer through the exterior wall.

The best long-term savings occur in climates where the average daytime temperature goes above and below the interior temperature. The concrete will act as a thermal mass, eliminating the need for heating or cooling spaces in those conditions. In a cold environment like Wisconsin, there are many benefits to using ICFs.

Case Study: Kendal Lofts

Photo courtesy of Bedford Developments

Location: Waukesha, Wisconsin
Units: 42
General Contractor: Bedford Developments
Architect: TDI Associates

One of the first projects that Bedford Developments worked on was in Waukesha, Wisconsin. The Kendal Lofts were the first of its kind: a 42-unit project with a new timber-framed interior with ICF exterior walls. Comprised of custom hardwood 8-foot doors, hardwood floors, and Amish cabinets, the project was born from an idea of Bedford Development’s now-retired owner Ken Miller.

As noted by Ryan Bedford, president of Bedford Developments and Miller’s son-in-law, Miller wanted to build a loft that resembled a warehouse but “did not like the thermal inefficiencies of lofts.” Miller was then inspired to use ICFs alongside timber.

"Today, you hear a lot about timber-frame buildings or mass-timber buildings," Bedford says. "The issue with this is that as green and sustainable as they say they are, they are really not green.” Essentially, the wood has to be cut down, transported by train to a mill, and once in the mill, it has to be glued together and transported again from one side of the country to the other. Many plants are located in Seattle, Oregon, and Canada.

For Kendal Lofts, Bedford Developments was able to ship reclaimed timbers from a building in Chicago, re-sawing and reusing them. The aggregate for the concrete, however, was locally sourced because, as Bedford notes, “concrete is one of the most locally reliable materials you can find across the United States.”

The entire exterior of Kendal Lofts is entirely ICFs. In the corresponding image, the gridwork of the timbers being placed into the ICFs and the stud walls on the interior can be seen. The post and beam timber-frame style of the interior offers the aesthetic factors of a warehouse, but the ICFs provide the building with energy efficiency.