Tuesday, June 14, 2011

Hawaii house design for high winds

We’ve been researching house designs that survive the best in Hawaii’s tropical storms with high winds. We found that hip-style roofs are considered aerodynamically superior in high winds and when combined with long overhanging eaves, they are even more stable because the eaves take some of the wind load off the walls.

Coming from the mainland, we find the look of hip-roofs unusual as they slope upward from all sides of a structure and have no vertical ends. A lot of people build gable-style houses in Hawaii because they are used to the design. Unfortunately, high winds can peel the gable roof from the house at the ends where the walls are exposed. Though gable-style roofs are easy to build and therefore common in track housing, they are not the best design for surviving the high winds of a hurricane or tropical storm.

Hip-roofs, which are more complex to build since they aren’t just a row of roof trusses, require special framing on each end where the roof slants back. The uniform height of the walls also makes it easy to attach gutters around the house which further protects the house and foundation from water and allows the water to be collected for other uses. Long overhanging eaves protect the interior walls and windows from rain and sun which reduces maintenance over time. In Hawaii, being able to keep the windows open all the time to maximize airflow greatly reduces the expense of electricity needed for fans and air conditioning.

The most simple hip-roof has a ridge over the top of the roof which creates two polygon sides and two triangle sides. Other hip-roof styles include the pyramid design where four equal triangular sides meet at a single point at the top of the roof, the cross-hipped design where two sections meet and form a seam, and the half hipped design where the standard hip roof has two sides shortened to create eaves.

Like most of the nation, we watched in horror the unbelievable destruction of Joplin, Missouri from the huge tornado. When TV cameras showed a street of houses that had been completely destroyed, one house remained with very little damage. The surviving house had a hip-roof design, a rare design on the mainland. Though we know that it does well in high winds we find it remarkable that it could survive the intense winds of a huge tornado. Driving around the island, we have a new appreciation of the roof lines in housing developments on Hawaii and are delighted to see how many new homes are being built with hip-roofs of one variation or another.


Adam said...

The place where the house will stand is one of the factors to consider in building one! The weather conditions should also be considered. Everything should be planned, from choosing the right location and materials to maintaining the house once it's done. Durability matters!

Adam Waterford

ChalmersAbrams said...

Very interesting. We build a lot of homes in a hurricane zone so this is definitely useful information. I'm sure your homes all use hurricane ties as well, right?
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Joan Price said...

This is interesting. Are people being educated about this? How is this impacting roofing companies in Hawaii? The effects of global warming are becoming more intense. It stands to reason that homes should be updated or built for maximum resistance to natural weather disasters.

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Flip Jork said...

The downside is going by the way that they are constructed, houses that have a this type of roof are susceptible to high winds thus they are not recommended to areas that experience regular extreme and strong winds.

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