Manmade Hailstorm Allows Study of Damage to Residential Home Building Materials

An indoor hailstorm bombarded a full size home inside the Insurance Institute for Business & Home Safety (IBHS) in Richburg, S.C. recently.

Close to 10,000 hailstones, measuring up to two inches in diameter pelted the 20 foot x 30 foot home, patio furniture and BMW sedan for approximately four minutes. When the test was over, visible damage could be seen on the roof, gutters and siding of the structure.

According to Dr. Tim Reinhold, senior vice president of research and chief engineer for IBHS, the hailstorm research team consisted of 14 lab employees as well as meteorologists.

Dr. Reinhold explains how the team determined the types of materials that were going to be used on the building structure.

“We wanted to pick some typical materials that you would see damage to. This system is really designed to hit the roof, and we’d hoped we would get more impacts on the wall, but we only got a few impacts on the wall. If we had had a two story, then we probably would’ve seen more damage to the wall sides,” he said.

He said an analysis f the damage found that about 90 percent of the claims are related to the roof and the soft metals up on the roof, including the gutters. “When you look at this building, you’re going to see a lot of damage to the gutters. You’ll see damage to the roofs. On the metal side, you’re going to see something that’s very typical to the kind of damage you get to metal roofs, with the indentations. There’s no leaking going on, but it looks pretty ugly. And then on the shingles, you’ll see particles blown out. There’ll be areas that over time would turn gray and be very ugly,” said Reinhold.

Recreating a weather event is no easy task and requires a lot of planning, according to IBHS scientist and meteorologist, Dr. Tanya Brown.

“We’ve actually been working on this project, in a conceptual sense, for four or five years. But as far as coming up with a cannon design, it took us about two years to prototype, come up with a design that we liked, and actually get it installed in the large test chamber,” said Brown.

Dr. Anne Cope, vice president of research, said this particular test was in planning for more than a year.

“We have been looking forward to this test since our facility was under construction. Hail is very unique. To get the hailstones right, and then to be able to propel them correctly, in an area that’s going to affect the building right, there were several moving pieces to that target and several different engineering designs that had to be worked out before this could become a reality,” said Cope.

Brown created the frozen ice balls by using a formula of tap water and seltzer water to attain the shape and density that closely mimics hailstones produced by Mother Nature.

“The hailstones were made up of a recipe of 80 percent seltzer and 20 percent tap water. We did that because, when you freeze the seltzer water, it actually traps some bubbles in the hailstones, and those bubbles help us control the density, to make it more realistic and more like what Mother Nature produces,” Brown said.

To make the testing even more realistic, the researchers made sure there was some wind speed involved with the hailstorm.

“There was a little bit of wind going. We had the fans going at about 10 or 12 miles per hour during the test,” Brown said.

The hailstones were fired from multi-barreled air cannons, also created by IBHS researchers, mounted on the catwalk of the research facility 60 feet above the house.

The results of the hail test were anticipated by the researchers.

“The results are pretty much what we expected to see. We saw lots of impacts on the roof, which is the most vulnerable place when it comes to hail damage,” Dr. Brown said.

According to Reinhold, the manmade hail had to be close to the real thing to get the same type of damage one sees after a real hailstorm.

“A big focus has been getting the hail right, but the tests that people have been using up to this point are either steel balls, which don’t really create the same kind of damage that you typically see out in the field, or solid ice balls, which are a bit better but still do more of an indent. It’s almost like hitting it with a ball peen hammer, as opposed to the kind of damage you see on a shingle roof, anyway, the particles blown out when it hits. What we’ve been working very hard at is trying to create something that’s much more realistic in terms of hailstorms, so that when we do the impacts, we get the same kind of damage you see in the real world,” Reinhold said.

The BMW parked next to the home was not part of the study, said Reinhold.

“It’s not really a part of the study. It was just to give more visualization, because I think people are more familiar with having seen up close cars in a lot after a storm’s gone through and see the dents in them, and we’ve got very similar dents in this car,” he said.

See the video.