Rigid Foam's Role In The New Energy Economy

Part 5: Surviving Hurricanes with SPF

By Mason Knowles

Spray polyurethane foam (SPF) is well known for its important role in creating sustainable buildings in the new energy economy. SPF is a great insulator, exhibits a high degree of sustainable characteristics, owing primarily to the minimal energy used in manufacturing the lightweight plastic, as well as decreased energy and transportation costs. It also is known for its durability and its ability to increase the structural strength through adhesion in some sealing applications for both residential and commercial buildings.[1]

Durability and increased structural strength are two of the qualities that contribute to SPF's great performance in extreme weather conditions like hurricanes or other storms. Other factors that can contribute to SPF's high performance in hurricanes include added wind uplift resistance and excellent resistance to damage from hail or other wind-borne objects.[2] Lightweight yet rigid, it provides extra strength and adhesion to help the roof stand up to the forces of nature.

In 1992 and 1996, the National Association of Home Builders (NAHB) tested the racking strength of various types of wall panels and concluded that panels with SPF increased the racking strength between 70% and 200%.[3] In 2005, Factory Mutual tested the wind uplift resistance of SPF roofing systems and concluded that SPF over concrete met the minimum of 990 psf (the rated capacity) for Class 1-990 wind uplift classification. In other words, it would take 990 psf of pressure to tear the foam from the concrete.[4]

Katrina Hits Mississippi

In September 2005, Hurricane Katrina grew from a small tropical storm in the Gulf of Mexico into a massive Category Five hurricane in a matter of days. With sustained winds of more than 175 mph, this storm was one of the worst on record. By the time the storm hit land, the winds had subsided to Category Four levels (125 to 145 mph), but the damage was still extensive. Whole buildings were uprooted and washed away by the 25-30 ft storm surge and were in some cases blown apart by the high winds. Long stretches of beachfront were flattened, and thousands were left homeless.

Two weeks after the storm, a wind investigation team sponsored by the Roofing Industry's Committee on Weather Related Issues visited the area. The team's role was to evaluate damage from Hurricane Katrina[5], and the team's area of investigation extended from Pascagoula to Biloxi, Mississippi. While driving along Highway 90 in search of roofs to evaluate, the team noticed SPF sprayed on the outside of a commercial building occupied by the Pascagoula Ice and Freezer Company. The team stopped and introduced themselves and asked the manager if they could investigate the roofs. The manager called the owner, David Gautier, who gave the go ahead.

A Family Business Grows

According to Gautier, "Our family has lived on the Gulf Coast of Mississippi since the mid 1800s. We founded the town of Gautier and have owned the Pascagoula Ice and Freezer Company since 1937. My father retired in 1985, and since then my brothers Warren and Andre and I have run the business. The freezers are used to store ice that is used by area businesses. We also process and wholesale shrimp that is caught locally.

"The first building was constructed at the turn of the century, and every 20 years or so new sections were added to the original building. The original construction was brick walls with wood tongue and groove decking. The total complex is approximately 45,000 sq ft.

"There is a loading dock area, a processing area, and four freezers, one for ice and three for shrimp, including a blast freezer. Temperatures range from room temperature in the processing room to -50F in the freezers and -15-200F in the blast freezer. The shrimp are sorted in the processing room, sent to the blast freezer for a quick freeze, and then stored in the other two freezers."

David continued his saga: "In the early 70s, the freezers were in poor condition. The cork had become saturated with ice and required a complete overhaul. We decided to go with spray polyurethane foam (SPF) for the new insulation because we had been convinced by our SPF contractor that it would be 'the best value for the money.' The foam makes the building a monolithic construction that holds it all together."

Early Adopters of SPF

"Bill Grant of Polyart Fabricators Inc., out of Mobile, Alabama, sprayed most of the foam. The first spray foam was completed around 1972. The last spray foam was installed to the outside of the walls and roofs of a section in the mid 1980s."

So, in 1972, the SPF crews tore out the old cork insulation, dried out the block walls and tongue and groove wood ceiling, and installed 3-5 inches of 2 lb SPF to the walls and ceiling of the blast freezer and 4-6 inches to the other freezers. The foam was trimmed at the edges with saws and sharp knives, and a cementitious covering was spray applied over the foam as a thermal barrier. According to Bill Grant, "When we started in 1969, we made a lot of our own equipment. Later we used other equipment manufacturers."

A Family Business Survives

Thirty-three years later, Hurricane Katrina destroyed a vast area of the Mississippi Gulf Coast. But at Pascagoula Ice and Freezer Company, even in the face of Category Four strength winds, the SPF insulated sections were not damaged. In other places that did not have SPF applied, however, pressurization from the high winds blew out portions of the roof deck.

The team asked Gautier if there had been other storms between Camille and Katrina. He smiled and said, "These buildings have not only survived Hurricanes Camille and Katrina but three other major storms as well--Hurricanes Frederick, Elena, and Georges. The spray foam definitely helped keep the buildings together.  

"In fact, my brother Warren's house was sprayed with SPF and it was the only house on the beach that was left standing after the storm surge."

Bill Grant adds, " Nothing could be more important for homes on the Gulf Coast than using SPF to hold the building together during a hurricane."

After the Storm

After the storm, the National Institute for Standards and Technology (NIST), located in Gaithersburg, Maryland, studied the impact of Hurricanes Katrina and Rita on structures in the damaged areas. Their recently issued report corroborates earlier research, and spray foam roofs were the only type of roofing system that NIST officials described as having performed "extremely well." Other sections of the report describe how spray foam roofing withstood Hurricane Katrina's winds without blow-off or damage to the flashings.[5]

These natural disasters also have changed building codes. Before Hurricane Katrina, Louisiana and Mississippi building codes contained no wind or flood provisions. Effective January 1, 2007, however, all new or rebuilt buildings in Louisiana must comply with the wind and flood provisions of the 2003 International Building Code and the 2003 International Residential Code. Mississippi is still working on a bill with similar requirements, and Alabama has passed a bill requiring enforcement of the 2003 IBC and IRC for certain types of structures.

Why SPF Works

How does SPF provide this extraordinary protection that allowed large sections of the buildings in Pascagoula to escape major damage from five hurricanes over 33 years? The answer is in the unique physical properties of SPF and how it is installed.

Adheres well.  SPF is sprayed on as a liquid and then expands to form a rigid foam plastic with great adhesive characteristics. Because it bonds tightly to a substrate it is very hard to pull off with high winds, as the Factory Mutual testing demonstrated.

Increases structural strength.  When installed to the inside of a structure, SPF can help glue the whole building together, increasing a building's overall wind and pressurization resistance.
 
Provides effective air barrier.  SPF can help eliminate air infiltration that can otherwise let the relatively high air pressure building inside escape through the roof deck, subsequently blowing off roofing membranes from beneath.

Minimizes building movement.  SPF, when installed to the outside of buildings, can help reduce the profile and minimize building movement so high winds are less likely to catch a corner or tear the substrate.

Durable.  Even if wind driven debris damages the surface of the foam, it can resist peel off and continue to provide water resistance to the interior of the building.

Flexible.  SPF has a degree of flexibility that can allow some movement without damaging its tenacious bond to the substrate.

Hurricanes and other natural disasters are having a huge effect on the building and construction industry, especially as architects, builders, and code officials come to recognize how well SPF performs in such extreme weather conditions.

Next Installment, Part 6--The impact of globalization on the polyurethane business

Notes

1. "Plastic Polyurethane Foam: Tying the Building Together," Modern Materials, June 2006.
2. "Shelter from the Storm: SPF and the Hurricanes of Florida," Modern Materials, May 2005; "SPF Roofing Works: Studies Dispel Myths and Prove Performance of SPF," RSI, April 2005; "Sustainability Characteristics of SPF Roofing and Insulation Systems," Modern Materials, November 2003.
3. Wall Racking Strength Testing Results from the National Association of Home Builders, 1992 and 1996.
4. "Spray Polyurethane Foam Insulation with Protective Coatings Produced with Alternative Formulations for use in Class 1 Steel Roof Deck Constructions", FM Global, January 2005. For a description of the FM wind uplift tests, go to www.sprayfoam.org/news.php.
5. For an executive summary of the NIST report, go to www.bfrl.nist.gov/investigations/pubs/NIST_TN_1476_ExecSum.pdf.
For the full report, go to www.bfrl.nist.gov/investigations/pubs/NIST_TN_1476.pdf.
6. See "Historic Hurricanes," www.hurricaneville.com. 

About the Author
Mason Knowles is the executive director of the Spray Polyurethane Foam Alliance (SPFA). He can be contacted via e-mail at masonknowles@sprayfoam.org.