Last week's combined snow and rain storms buckled roofs in Portsmouth and Derry on Friday and prompted state officials to warn of the potential danger of collapse.
But a new product from a Barrington engineering company could give building owners and municipalities an early warning when heavy snow loads are making roofs dangerously unstable. The SnowScale was developed by Christopher Dundorf, founder and president of 2KR Systems LLC.
Designed to measure the water content of the snowpack, the SnowScale has been used by researchers in New York state to monitor snow melt and potential flooding from spring runoff.
Now Dundorf wants to deploy the technology on roofs across New Hampshire and beyond. And he's enlisted the talents and enthusiasm of students at the University of New Hampshire-Manchester to develop a prototype.
Here's the problem Dundorf set out to address: "You can't use snow depth to tell you how much water is in the snowpack."
That's because - as anyone who's had to shovel this winter knows - light, fluffy snow weighs a lot less than the rain-laden stuff that arrived late last week. And when it comes to snow loads on roofs, that's a critical difference.
A typical 20,000-square-foot retail store could have 300 tons of snow on the roof, Dundorf said. Late in the season, when the snow compresses, it can weigh 30 pounds per cubic foot.
His first client for the SnowScale was New York City, which depends on snow melt from the Catskill Mountains for its water supply. Researchers have deployed a network of SnowScales on the ground in upstate New York.
Dundorf had the idea that the same system could be used to measure the weight of the snow that collects on the flat roofs that are common all over the Northeast, from warehouses and big-box stores to schools.
Snow clearing, he said, is a hugely costly operation for retailers and municipalities. Officials at one retailer told him they spend $10 million to $15 million a year to clear snow from its stores' roofs.
But a roof collapse can be catastrophic. So each winter, it becomes a critical decision: To shovel or not to shovel?
Dundorf figures his SnowScale technology could inject some science into the equation.
Deploying a network of sensors to measure the water content of the snow on roofs could give building managers the data they need to make smart decisions, he said. Software can analyze data almost constantly; once a critical weight is detected, alerts will be sent to building managers.
"This would warn them when the snow load is reaching a safe limit threshold," he said.
But to make the product commercially viable, Dundorf said, "we realized we needed a turnkey system."
"That means you basically take it out of the box, you set it up, you hit the power button, you load the software and it just runs."
He needed electrical engineers to adapt the SnowScale for rooftop use. And he needed software engineers to write the database programs to collect and store sensor readings.
So Dundorf turned to the New Hampshire Innovation Research Center at UNH in Durham, which funds projects that lead to job and business growth.
The IRC put him in touch with Christopher LeBlanc, assistant professor of engineering technology at UNH-Manchester, and Mihaela Sabin, associate professor of computing science at the college. Each put together teams of three students, who began working on adapting the SnowScale to rooftop use last month.
"Chris approached my team and said, 'I want to take this, I want to shrink this, make it smaller, and I want to be able to easily deploy it on a rooftop.'" LeBlanc said. "Ease of use was the design point he was really stressing."
He noted it's the first project funded by the IRC at the brand-new Engineering and Technology Laboratory that LeBlanc started at the UNH-Manchester Millyard campus with a $75,000 grant from an anonymous donor.
Colby Johnson, 22, of Manchester is on the software design team. He's a 2009 graduate of Manchester Memorial High School, a member of the New Hampshire Army National Guard and a new father.
Johnson said he knows firsthand how heavy moisture-laden snow can be here in New England. With the snow-load project, he said, "what interested me was that it was a solution to a real-world problem."
"I like playing around with things and making them look appealing and user-friendly and have a good little functionality to it."
Sabin said she jumped at the chance to get her students involved. "I think what was also very appealing was the collaboration between engineering technology and computing," she said.
Casey Hoefer of Sutton, 25, is a senior electrical engineering major. By the time the prototype is ready for testing this spring, he said, "we're probably going to have to simulate the snow."
But the project just got funding from New Hampshire EPSCoR (Experimental Program to Stimulate Competitive Research), established by the National Science Foundation in 1979 to strengthen science and engineering infrastructure in states that historically have received less in federal research grants.
That grant will allow the UNH-Manchester students to continue their work into the summer, and Dundorf said he hopes the actual product will be ready to deploy on roofs in time for next winter.