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Knock this house down: science will thank you Add to ...

While there will be no huffing and puffing at the University of Western Ontario's soon-to-open Three Little Pigs facility, the two story, suburban-style test house will eventually get blown down.

Well, sort of blown down.

In truth, the home-levelling force won't be actual wind, but rather pressure generators attached to the house, which, at their greatest, will equal those generated by the building-levelling winds of a Category 5 hurricane.

Why build a house just to knock it down?

"We believe that weather is changing and that more big storms are heading our way and we have to turn to science to show us how to build a home that will hold up to that kind of weather," is how Paul Kovacs of the Institute for Catastrophic Loss Reduction -- a Canadian insurance industry umbrella group which gave initial funding to Three Little Pigs -- describes one problem.

One irony is that some people in the construction and insurance business believe that modern houses are in fact over-built.

"We expect that the research team will identify aspects of over-engineering in current home construction practices, areas where savings are possible without a compromise in safety," is how Mr. Kovacs delicately describes this possible spin off of the research.

But all of this depends upon how well the new $7.8-million facility being constructed at the grounds of the London airport actually works. One key component is the performance of 100 pressure actuators which are being built by the British firm Cambridge Consultants. These are attached to a steel structure outside the test home and from there, exert various forces on the house itself.

Why pressure generators and not an actual wind-generating machine? Using the giant fans like those that power boats in the Everglades, such a device has been set up in a laboratory in Florida. "It is visually quite impressive, because you can see water and shingles being ripped off but you aren't actually getting the gradients of the pressure," says Mike Bartlett, a professor of civil and environmental engineering at Western.

That is to say, you aren't mimicking the effects of real storms in which wind comes not as a steady blow but in gusts. The computer-controlled actuators can change forces several times a second and thus imitate a storm's windy variability.

Another key component of the test house is its designed ordinariness. What the insurance and the construction industries are interested in is the effect of winds not on an ideally constructed house but on the average home with an average number of carpentering flaws in its construction. To obtain the necessary ordinariness, Western has employed Fanshawe College home building students to construct the mock house.

Prof. Bartlett rather proudly points out that when constructing the test home, the students took a shortcut and installed some plumbing by cutting through a support beam. While a classic construction no-no, even with it, a group of Southern Ontario building inspectors who looked at the test house rated it on average with the buildings that they see in their daily experience.

The project may also shed light on how to minimize the impact of wind. Looking at the aftermath of hurricanes in the U.S., one suspicion is that hand-nailed roofs stay on better than machine-nailed ones. This may be, suggests Prof. Bartlett, because carpenters with a hammer can tell when a nail has missed but can't when a machine drives it in.

But the Three Little Pigs is not all about pushing on walls and seeing what happens to the structure. The project is also trying to understand the relationship of house construction to another growing insurance bugaboo -- mould.

"One my colleagues in the U.S. likes to say that even the stupidest of the three little pigs didn't build his house out of paper," is how University of Toronto biologist and Three Little Pigs researcher James Scott describes the modern conundrum.

Paper, or more specifically, plaster board and its kin, has over the last 50 or so years become an intrinsic component of housing construction. And if there is anything that mould loves it is paper, says Prof. Scott. While government has tried to address the issue with revised building regulations and industry has introduced less mould-prone materials, as with wind damage there is actually very little science that relates home construction to subsequent mould formation. What Prof. Scott and Western engineering professor Eric Savory have done is instrument outside walls on one of the permanent structures at the Three Little Pigs to measure the growth of mould as rain and wind hit the building.

So the Three Little Pigs project will look at brick, wood and paper buildings, but what of the classic straw house that was also blown down by the Big Bad Wolf?

That too may be in the cards. Colin MacDougall, one of Prof. Bartlett's former students, is now a professor at Queen's university, and actively involved in testing straw as modern building material. He hopes in the future to use Three Little Pigs as a test lab to measure the durability a straw-built house.

One result: Early retirement for the Big Bad Wolf.

 

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