As part of the IBHS Research Center Grand Opening, IBHS conducted a test in which two full-scale, two-story, 1,300-square-foot houses were placed next to each other in the test chamber—one built using conventional construction standards common in the Midwest, and one built to IBHS’ FORTIFIED code-plus standards for the Midwest. Both were subjected to the same severe thunderstorm conditions.
The initial research focus was on roofs and roofing-related issues, such as:
- Developing relationships between current test standards and performance of roofs in simulated windstorms
- Identifying effective methods to provide back-up water intrusion protection when primary roof cover is damaged
- Identifying fixes for water intrusion and wind-borne firebrand intrusion via roof venting systems
- Simulating wind-driven hail events and evaluating associated damage to roof covers, as well as identifying solutions
- Initiating research into aging effects on roof performance in extreme events
- Developing cost-effective methods for retrofitting various roofing systems to mitigate damage and losses
Straps were added to the FORTIFIED house to provide a continuous load path, using metal strapping from the roof to the second floor, between the second and first floors, and from the first floor to the foundation.
Additional differences between the conventional and FORTIFIED houses included:
- Use of ring-shank nails to attach the roof and wall sheathing on the FORTIFIED house, instead of the staples typically used in conventional Midwestern construction
- Installation of a sealed roof deck (4 inch-wide ice and water shield self-adhesive strips) over the seams between the roof sheathing
- Installation of high-wind rated shingles on the FORTIFIED house, versus an unrated three-tab shingle on the conventional house
- Installation of a high-wind rated vinyl siding product on the FORTIFIED house versus a typical unrated vinyl siding product on the conventional house
- Changing the entry doors from in-swing on the conventional house to out-swing on the FORTIFIED house
During the thunderstorm and frontal wind scenarios, both buildings experienced some damage to flashing and soffit materials, and the conventionally constructed house experienced damage to siding and shingles. As wind speeds were increased using the Hurricane Ike records, the front door of the conventional house suddenly blew open (with wind speeds at about 100 mph) allowing wind pressure to build up inside the house. The entire structure was reduced to a pile of rubble in less than four seconds. Because the FORTIFIED house had an outward opening door, it did not blow open, and consequently, was never exposed to the same buildup of internal pressure experienced by the conventional house.
During review of video captured during the collapse of the conventional house, IBHS staff noted that when the front entry door blew in, the front wall broke loose at it base and the side walls appeared to balloon out. This raised questions about how well the side walls were attached to the second floor system. However, IBHS engineers decided against making a modification to the FORTIFIED house at that time in order to keep its strapping consistent with typical high wind prescriptive solutions. The original FORTIFIED house was repaired and a second FORTIFIED house was built along with a new conventionally constructed house.
The entire structure was reduced to a pile of rubble in less than four seconds.