Building safer homes
By Nicole Laidler | March 20, 2013
Everyone loves a summer breeze, but when the winds pick up to hurricane force you’d better watch out. Each year, extreme weather claims lives and destroys property, in both the developing and developed world.
Last October, Hurricane Sandy ripped through parts of the Caribbean before heading north to devastate New Jersey and New York, killing around 285 people and causing over $71 billion in damage.
And while science can’t stop Mother Nature, a team of Western University wind engineers are hoping to minimize her impact by learning how to build a better home.
The Insurance Research Lab for Better Homes is a first-of-its-kind facility that allows researchers to simulate and study realistic damage to full-scale houses from wind, snow and rain within a controlled environment.
“Every time there’s a wind storm people say it’s an act of God,” said Western Civil and Environmental Engineering professor Greg Kopp, who studies the effect of extreme wind on buildings. “It’s not an act of God. We built this house and put it here. We can do something about it.”
Opened in 2006, the $6.8 million facility allows researchers to simulate the force of the wind up to an equivalent of about 200 miles per hour – the worst of a category 5 hurricane – and study how it rips a house apart.
Rather than actually blowing hurricane force winds over a full-scale home, the project recreates the effects of the wind by first testing miniature models in Western’s Boundary Layer Wind Tunnel Laboratory.
“We did a wind tunnel study with about forty different house shapes to study the aerodynamics of houses and how wind forces act on them,” Kopp explained.
Those forces are replicated using full-scale homes in the Insurance Research Lab for Better Homes by mounting nearly 100 pressure boxes to a framework surrounding the test home and collecting data as it is torn apart.
Kopp, whosse team developed the technology to apply the pressure loads, compared the process to a vacuum. “When wind blows over a house, or any structure, it creates pressure distribution. It wants to lift the house.”
So far, two full-scale homes have been built, blown apart, and studied. “It doesn’t sound like a lot, but it gives you plenty of data to develop engineering models to predict behaviour under different wind conditions,” Kopp said.
The ultimate goal, he noted, is to recommend affordable building code changes that will make homes less vulnerable to extreme weather conditions.
“It sounds simple, but it really comes down to nails,” said Kopp. “If you make the nail a little bit longer and make the head of the nail a little bit bigger all of a sudden you can withstand quite strong winds.”
Metal hurricane straps that anchor roof trusses to a home’s load bearing walls are another relatively inexpensive way to hold a roof in place, even during an F2 tornado, he said.
The research has already prompted a modification to the Ontario building code, which now requires more nails to be used to secure roof sheathing. Kopp hopes the change will soon be adopted nationally.
This summer, the Insurance Research Lab for Better Homes will be used to study how a home’s walls collapse once the roof has been blown off. Collapsing walls are a common cause of injury and death during severe wind storms, Kopp noted. “Hopefully we can make some building code recommendations to help deal with this issue,” he said.
“We could build a house that could withstand any tornado, but nobody wants to pay for it,” he said. “The question is, can we make them more resilient without adding cost? And the answer is yes. That is what we are working on.”