IMPACTS OF TEXAS DEPARTMENT OF INSURANCE ADOPTION OF IBC 2018 FOR WINDSTORM CERTIFICATION
IES has extensive experience on past and current projects located in the first-tier counties along the Texas Gulf Coast where the high wind provisions of the International Building Code and the certification requirements of the Texas Department of Insurance (TDI) apply. Our staff includes licensed engineers accredited by TDI as Windstorm Inspectors since 1999.
We reached out to the Director of our McAllen office, Jason Irish, PE and our Project Engineer, Ramon Lopez, EIT to ask what impacts of the Texas Department of Insurance’s adoption of the 2018 windstorm certification they are experiencing, as well as, our firm President, Justice W. Edge, PE on what determines if a project necessitates certification and how to advance successfully.
Prior to adopting IBC 2018, TDI was using IBC 2006. What is different about wind pressure values from IBC 2006 to IBC 2018?
When TDI was based on IBC 2006 the wind pressures were calculated per the ASCE-05 standard. ASCE-05 wind pressures are at service level which represent the actual imparted loads on a structure. IBC 2018 uses the ASCE 7-16 standard and the wind pressures are at ultimate levels. This means that the wind pressures are increased to include load factors that are part of the safety factors we use for design. When required, according to Jason, the ultimate wind speed can be converted to service wind speed (mph) with the equation V asd = V*(0.6)^(1/2).
Ramon adds that 2018 updated the building wind loads reference from ASCE 7-05 to ASCE 7-16. The biggest change is in IBC 2006/ASCE 7-05 code the catastrophe zone areas were broken up into 3 zones; Seaward, Inland I and Inland II and the windspeed was service level (ASD) reference. With the new code the zones are divided by wind speed in mph at the ultimate level reference (LRFD).
Ok. So, in general, when the wind pressure values are reduced to service level, has the wind pressure increased from IBC 2006 to IBC 2018?
Jason shares that. in general, the IBC 2018 wind pressures decreased in areas that are not hurricane prone based on wind data studies. In hurricane prone regions such as along the gulf coast of Texas the wind pressures remained about the same. However, in IBC 2018, roof wind pressures increased since IBC 2018 revised roof pressure coefficients based on data from wind tunnel studies at Texas Tech University. Additionally, based on the wind tunnel studies, roof with slopes less than or equal to 7 degrees (1.5/12) the corner zone areas increased and are calculated based on the height of the building.
The loads in general are approximately the same, per Ramon, but some of the wind zone areas on building zones have been modified and winds pressures for these modified areas increased.
What about wind-borne debris? How has this changed? If my project is north of Highway 77, am I still ok without impact testing of my windows?
Jason notes that TDI is no longer using a map that designates areas as Inland I, Inland II, or Seaward. The new TDI map covers the same counties along the gulf coast area, but they are all just called “designated catastrophe areas”. In IBC 2018 wind borne debris regions are located in areas where the wind speed is 140 mph or greater and 130 mph or greater if within 1 mile of coast. If your north or west of Highway 77 the wind speed is likely to be less than 140 mph so you are not in a wind-borne debris region for Risk Category I, II, or III buildings and impact resistance of windows are not required.
Ramon confirms that in IBC 2006/ASCE 7-05 code impact resistance glass and glazed openings were required for projects within hurricane-prone regions that are within 1 mile of the coastal mean high water line where the basic wind speed is 110 mph (ASD) or greater. Under the new code, impact resistance is required for windspeed of 130 mph (LRFD) or greater.
What about testing standards? Have the testing standards changed between IBC 2006 and IBC 2018?
Per Jason, little has changed between the testing standards of IBC 2006 and IBC 2018. Gazed openings within 30 feet of grade still must meet the requirements of ASTM E 1996 large missile test and glazed openings greater than 30 feet must meet ASTM E 1996 and small missile tests. IBC 2006 references E1996-04 and IBC 2018 references ASTM E1996-14a. When TDI was under IBC 2006 there was also the requirement to meet Texas Revisions to the 2006 IBC. Since TDI has fully adopted IBC 2018 without revisions exterior doors and garage doors without glazing in the seaward zone are no longer required to have missile testing.
Testing standards are the same between the two codes, shares Ramon, but TDI is more open to accepting other testing for example; the testing for Dade county, which in the past was not accepted.
What makes my building project require windstorm certification by TDI?
Justice Edge advised that windstorm certification is needed to obtain windstorm property damage coverage in Texas. While this decision comes down to an individual building owner’s risk tolerance, it is also a major factor in whether a lender will fund the purchase of a property. If the property is not capable of obtaining windstorm property damage coverage, this makes the collateral for the load susceptible to risk and lenders do not like risk. Also, many authorities having jurisdiction in the first tier counties will not issue a permit for construction without the submission of a WPI-1 application to TDI and will not issue a certificate of occupancy without the submission of a WPI-8 application to TDI. In those cases, it is no longer just a decision regarding property insurance.
What is your advice for a successful project that requires windstorm certification by TDI?
The key to a successful project in the first-tier counties is researching the basis of design products that are specified for the building envelope. The architect and engineer need to work together to ensure that the testing requirements for the building envelope components are clear and that the basis or design products meet those testing requirements. If that research does not happen until the construction phase, change orders are the result.
To learn more about IES’s experience on projects requiring Texas Windstorm Certification or any of our other engineering solutions please don’t hesitate to reach out to our offices.