An increasing number of asphalt roof shingles are being touted for their hail impact-resistance. Hail resistant shingles are desired because the process of removing and replacing a roof is costly and disruptive. Furthermore, many property insurance carriers offer significant discounts on insurance premiums when impact-resistant shingles are installed. Haag performed a study on impact-resistant asphalt roof shingles to evaluate their performance.

The study involved testing five different impact-resistant shingles with two different impact testing protocols. One of these protocols (UL 2218) subjects roofing products to steel balls dropped from specified heights, developing kinetic energies that are comparable to free-fall energies of hailstones measuring 1-1/4, 1-1/2, 1-3/4, and 2 inches in diameter. Products that pass the test are given impact ratings of Class 1, 2, 3, or 4, respectively. The other protocol (ANSI/FM 4473) subjects roofing products to propelled ice balls measuring 1-1/4, 1-1/2, 1-3/4, and 2 inches in diameter, at specified kinetic energies that comport to energies of free-falling hailstones of these sizes. Products that pass ANSI/FM 4473 are also given Class 1, 2, 3, or 4 ratings.

In addition to hail impact testing, Haag utilized hot solvent desaturation procedures to extract the reinforcements from the shingles by dissolving the asphalt or modified asphalt bitumen from the shingles. This allowed the shingle reinforcements to be examined for fractures or strains caused by the impacts without hand manipulation which can initiate damage.

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