HOW IS
wreak havoc. As Rem Brown, IBHS senior
engineering manager, notes, “homes located in areas with high tornado risks
generally are not constructed to withstand severe high winds, because design wind speeds which form the base of
building codes and standards are usually
less than 110 mph.”
Fortunately, wind loss mitigation steps do
not require the force of law to be implemented. Home and business owners can
take steps any time to harden their new or
existing structures, using IBHS or federal
guidance (which aligns closely with IBHS).
Brown says that improving building construction should be a priority in the central U.S.
One way property owners can improve
building construction is by following
IBHS’ FORTIFIED HomeTM standards for
the high winds and hail that are often associated with tornadoes. The FORTIFIED
program features practical, meaningful solutions for new, as well as existing
homes, including creating a continuous
load path and reinforcing garage doors to
withstand high wind speeds.
It is important to note that FORTIFIED
standards are not designed to prevent
damage from EF-3, EF-4 and EF-5 tornadoes which pack the highest wind speeds,
but they can reduce property damage
caused by lower level tornadoes and near
the edges of severe tornadoes.
EF-5 TORNADOES
ARE VERY RARE
“At a certain point, physics will overwhelm
even the best engineering,” Rochman
said. “Fortunately, the vast majority of tornadoes in the U.S. every year are lower
level EF-0, EF-1 and EF-2 storms, for which
there are numerous things we can do to
reduce damage.”
According to the National Climatic Data
Center (NCDC), 77 percent of tornadoes
have wind speeds less than 110 mph, and
more powerful tornadoes, such as those
that devastated Moore and El Reno, account for only one to two percent of tornadoes affecting the U.S. each year.
A Tornado Rated?
In addition, Dr. Tanya
Brown notes that damage documented after
The Enhanced Fujita
EF Rating
Wind Speeds
3-Second Gust (mph)
the Moore tornado re(EF) Scale is a set of
vealed that only one
wind estimates (not
EF-0
65-85 mph
single point of the tormeasurements) based
nado’s path showed
on damage. The EF
EF-1 86-110 mph
EF-5 damage. “Even
Scale is used to assign a
in violent tornadoes,
tornado a ‘rating’ based
there is not a mile wide
EF-2 111-135 mph
on estimated wind speeds
swath of EF-5 damage,”
and related damage.
says Brown. “During
EF-3 136-165 mph
Tornado-related damage
the biggest event, the
is surveyed after the storm
damage is confined to
EF-4 166-200 mph
and is compared to a list
a narrow path. If you
of Damage Indicators
are on the edges of
(DIs) and Degrees of
a tornado’s path, enEF-5
>200 mph
hanced construction
Damage (DoD) which help
will definitely help you.”
estimate the range of wind
A recent report on the
speeds the tornado likely produced and it is from this
2011 Joplin tornado by
information that a tornado is given an EF rating.
the American Society
(Source: National Weather Service)
of Civil Engineers
shows that more than
83 percent of damage during the pow- Oklahoma will follow Joplin’s lead and
erful EF-5 tornado was caused by wind improve building standards to reduce
speeds of 135 mph or less, the equivalent damage from storms remains to be seen.
of an EF-2 tornado. In addition, only four “It would be very beneficial to have a
percent of damage from the storm could strong statewide building code in states
be linked to an EF-4 tornado, while inves- that are prone to tornadoes. The goal is to
tigators found no EF-5 level damage at all. reduce the amount of damage that occurs
The study concluded that because poor- as much as possible, and stronger minily built structures were not able to with- mum standards would help,” Rochman
stand hig