1:5:10:365 EcoTip Blog

January 28, 2009

2009 Ice Storms

Here we go again. over a million people are without power due to ice storms across the Midwest stretching down into Texas. Ice storms are a huge problem for buildings constructed in areas where they are not common.

One of the things that is happening is warmer temperatures in the outer atmosphere mean there is more moisture. When this moisture condenses it begins to fall as rain. If surface conditions are below freezing, the rain drops freeze and become ice. When upper atmosphere temperatures are cold the water falls as snow not rain. Snow is less damaging since it weighs about 1/10th as much as ice.

In addition to the power outages – we should anticipate an increase in building roof collapses. Steeper sloped roofs are better equipped to deal with this extreme weather where at least some of the ice will generally slide off. Flat roofs tend to accumulate the ice and are more likely to collapse from the load.

Some areas have been reported to already have about 6 inches of ice with another 6 inches potentially falling in the next 24 hours. Twelve inches of ice on a roof weighs about 60 pounds. That is a huge amount of weight for a roof since many roofs in areas that are not commonly exposed to the weight from ice and snow have been built to hold a minimum of twenty pounds. 

We should also anticipate problems with frozen plumbing and ice dams.

For more information about these topics type the following key words into the search engine for this site (right hand column) do one search at a time: ice dam, plumbing, thermal imaging, roof, can light, frozen.

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If you need help with damage – the  IICRC is the place to go for a referral to a specialist in these types of problems. The following is from their web-site:

The IICRC is a nationally accredited, non-profit certification body that works to protect consumers from deceptive and unreliable companies in the cleaning, restoration and inspection industry. IICRC-Certified Firms and Technicians must meet the highest industry standards to maintain their good standing.

IICRC offers water and flood damage tips at http://www.certifiedcleaners.org/ts_tips_advice.shtml you can use their directory search to help find a certified firm or call 1-800-835-4624.

John Banta is the author of Extreme Weather Hits Home: Protecting Our Buildings from Climate Change.

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April 11, 2008

:102 Roof Slope

Filed under: :102 Roof Slope — Tags: , , , , , , , , , , , , — John Banta @ 12:01 am

Welcome to today’s 1:5:10:365 Tip for becoming a better steward for our home and planet.

1:5:10:102 EcoTip: Roof slope makes a great deal of difference in the uplift force exerted as wind flows over the top. The steeper the slope the less chance the roof will fly away.

Credit: Simpson-StrongTie Co., Inc.

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Additional Information

Suggested Review – :098, :099, :100, :101

 The following excerpt is from my book – Extreme Weather Hits Home:

The same forces that allow airplanes to fly are exerted on roofs exposed to strong winds. The angle of your roof can make a great difference to whether your roof will stay intact or sail away like the wings of a plane. Research conducted by Clemson University at their wind load test facility has demonstrated that a category 5 hurricane can develop uplift as much as 100 pounds per square foot. This is typically enough to lift a house right off its foundation. The lifting force is greatest for flat or low-slope roofs. As the angle of the roof increases the force drops. A roof slope between 4.5 and 6.5 seems to be the least aerodynamic. A gable roof will act more like the wings of a plane than a hip roof which slopes down on all sides, helping to cancel lift forces from all directions (Clemson).

The lifting force of wind is tremendous. When airplanes taxi for takeoff they achieve speeds in the 50 to 150 mph range, which is about the same as those speeds found in damaging winds. The roof of your home has a much greater lifting surface area than most airplane wings, allowing the entire roof to be lifted off the house. Once the roof is gone the walls will easily collapse. The lifting force for a roof — just like an airplane wing — is caused by the Bernoulli effect of air passing over the top of the roof creating lift. Some people have advised keeping your windows open to help neutralize the interior building pressure but this doesn’t really work and will let in lots of water causing additional damage to the interior. The best way to keep homes intact when exposed to strong winds is to keep them in one piece and securely fixed to the foundation.

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