Demonstration Site: Mercedes Homes/FEMA – Melbourne, FL
August 2001 – Mercedes entered into a project with PATH, the Federal Emergency Management Agency, Fannie Mae, and the Florida Energy Extension Service (FEES) at the University of Florida to exploit the enhanced wind-resistance of the poured concrete exterior envelope of their latest series of homes as value engineered by the Consortium of Advanced Residential Buildings (CARB) of DOE’s Building America program.
October 2001 – Steven Winter Associates (SWA) contacted the civil engineer at the University of Florida to verify the previously established timeline and task guidelines. The storm resistance capacities of Mercedes’ old concrete block design and new poured concrete design will be quantified and compared to both the current Southern Building Code and the upcoming Florida Building Code. The results were the subject of a presentation at the University of Florida.
December 2001 – PATH coordinated the engineering analysis of standard block and solid pour concrete houses performed by the University of Florida. Loads were established and compared to code.
January 2002 – An engineering analysis identified those components subject to failure under conditions established by the 1997 Southern Building Code.
February 2002 – Engineering analysis of the existing concrete block homes indicated they are under-engineered, with more “weak links” than anticipated. Preliminary analysis of the solid pour concrete homes compared favorably.
March 2002 – Projectile missile testing was performed on windows and shutters using standard and laminated glass and two different shutter configurations. An aluminum shutter and laminated glass combination passed the destructive test but with its integrity compromised.
April 2002 – Additional windstorm analysis of the concrete and concrete block home roof truss tie-down, covered porches and garage doors revealed an advantage for the truss tie-downs for the concrete homes versus the standard block homes.
May 2002 – Results of the structural hold-down analysis of the standard block houses created an analytical discrepancy between the in-house engineering performed by Mercedes and the consulting engineer from the University of Florida. Engineering concluded a double bond beam was required for the top course, while Mercedes maintainws a single course bond beam was sufficient to meet local wind zone tie down requirements. This discrepancy would not affect the new concrete homes, which out-performed the block houses in wind storm resistance according to both engineers.
June 2002 – Draft Report outlining the structural wind-resistance capabilities of the concrete block home major components was completed. This stage of the report excluded the smaller structural components, specifically: window anchorage; garage door; overhang soffit specifications; and front entry and rear porch attachments.
July 2002 – All aspects of the initial Draft Report on the base-case concrete block wind-storm resistance were completed, including the smaller structural components. The structural engineering computer modeling package for the home was also completed. This allowed for a quick one-by-one alternate component analysis to systematically review options for cost-effective “weak-link” component hardening.
August 2002 – The Executive Summary of both volumes of the wind-resistance engineering study was completed. The “weak-link” components were identified in the results of the engineering study.
September 2002 – All baseline work on the standard practice concrete block homes were completed and the conclusions were reviewed. The results pointed to the need to “harden” several specific components in order to meet the desired wind resistance levels. These included the obvious (windows) and not-so obvious (under-sized bond beam). As window hardening would be required in the concrete homes as well, PATH pursued various laminated glass technologies as well as shuttering systems.
October 2002 – Based on results of the completed “existing conditions,” structural analysis of the original block homes and new line of concrete homes, defined “weak-link” system components were reviewed.
November 2002 – Pricing was established for required upgrades or specification changes needed to satisfy the 125 mph windstorm requirement. In addition, PATH reviewed the structural calculations with civil engineers from the University of Florida. This resulted in the positive identification of currently required design changes needed to meet the established 125 mph wind-storm conditions. Pricing for those design changes and specification upgrades was begun.
December 2002 – PATH met with University of Florida structural engineers to review and verify the findings with regard to the wind resistance of the CMU homes and the new concrete homes. Some level of non-performance was indicated in both housing forms. Structural improvements were discussed and agreed upon; not agreed upon was the concrete wall under load. In addition, the team meeting in Melbourne resulted in a plan to finalize the concrete home analysis and apply cost considerations. Research began for a roofing material that is rated above 110 mph.
February 2003 – PATH found new roof shingle developments within the Owens Corning research and development group. Owens Corning developed a new 130 mph asphalt shingle product called “Weather Guard HP” that was to be available March 17th, 2003 for shipment.
March 2003 – PATH contacted the Weather Guard HP distributor in Jacksonville, Florida requesting the shingle specifications.
April 2003 – Weather Guard HP shingles became available. PATH established three roofing options for the wind-resistant home: the upgraded shingles; a self-sealing underlayment with the standard shingles; and a self-sealing underlayment placed at the roof decking joints only.
May 2003 – The three roofing options for the wind resistant prototype house were presented to Mercedes for consideration. The three options include: Owens Corning “Weather Guard HP” 130 mph shingles; full self-adhering supplemental underlayment with standard shingles; and self-adhering underlayment strips only at the decking joints. Due primarily to cost considerations, the most likely method for the prototype is additional protection at the decking joints.
June 2003 – Additional research on the least costly wind-resistant roofing covering assembly was conducted with several modified-bitumen flashing tapes investigated for use as the roof deck “joint-only” sealing method.
August 2003 – The last issue to be resolved, the roof covering for the wind storm resistant house, was finalized. The search for an affordable shingle focused on two potential procedures: A “joint only” secondary roof deck protection using peel-and-stick flashing tape at the roof deck joints; and a full roof deck covering of peel-and-stick membrane. The full deck covering was found to be less expensive, as it eliminates the need for the roofing felt, which is still required with the joint-only solution. At the time, Mercedes Homes was planning a new subdivision between Melbourne and Orlando, and expressed interest in building the model homes with the wind-storm-resistant upgrades.
NOTE: Due to a time lapse in consulting contracts, the work on this project was suspended for approximately 12 months.
September 2004 — With the 2004 summer hurricane season already having produced two major storms, PATH researchers and Mercedes discuss and agree upon renewal of the project. Team members FEMA, and FEES are included in the discussion and are enthusiastic in re-committing to the project.
October 2004 — Representatives of PATH, FEES, and Mercedes Homes tour storm damaged homes following the fourth major storm to hit the state. Preliminary damage cost estimates state-wide is in the tens of billons. Field inspections of the Mercedes concrete homes reveal no structural wind-storm induced damage. Various avenues of water-intrusion damage were however noted in several of the non-concrete homes inspected.
December 2004 — A second follow-up visit was made to re-inspect the homes with water-intrusion to confirm the manner and means in water entered the homes during the storms. Based on this analysis, a series of specification and component design changes were initiated to mitigate the determined means of water entry.
January 2005 — A meeting was held in Orlando with representatives of PATH, Mercedes Homes, FEMA, University of Florida, Tower Hill Insurance, and building code enforcement officers. PATH presented its findings on the water entry modes and recommendations for changes to those identified “weak-links”. Mercedes Homes received the recommendations very positively and agreed to build a new model home featuring the concrete construction and the water-intrusion resistant details.
February 2005 — A site was selected for the new model home and the specifications refined. Construction of the hurricane resistant home began in Rockledge, Florida.
March 2005 — As construction of the home continued, Mercedes also began a second home — a two-story concrete block featuring completely filled block cores as well as the other water intrusion mitigation details. The features in both homes were for planning and communication purposes broken down into three major levels of protection: Structural wind-storm resistance; water intrusion mitigation; and post-storm and recovery.
April 2005 — Construction on both homes proceeds. Completion is planned for the beginning of June, also the first official week of the hurricane season. Planning for an opening event and press conference to unveil the homes is initiated.
May 2005 — June 9th is selected as the date for the planned media event. Construction proceeds on schedule. Mercedes provides continual construction updates to team members and while also documenting cost and production realty issues.
June 2005 — The homes are completed and the hurricane-resistant model home event draws over a hundred attendees including four television crews, numerous newspapers, and other media outlets. Mercedes has at this point already adopted most of the specification changes as standard practice and offers the others as options including: hurricane shutters; generators; and generator-ready electrical panels.