This is your very first post. Click the Edit link to modify or delete it, or start a new post. If you like, use this post to tell readers why you started this blog and what you plan to do with it.
This is your very first post. Click the Edit link to modify or delete it, or start a new post. If you like, use this post to tell readers why you started this blog and what you plan to do with it.
HOUSTON METHODIST WEST PHASE II EXPANSION
After opening its doors just five years ago, Houston Methodist West Hospital is currently expanding its campus to better serve the community. To ensure the expected life cycle is realized for the Houston Methodist West Hospital Phase II Expansion, Zero/ Six provided construction administration services, including peer reviews, submittal/shop drawing reviews, and observation of the ongoing construction of building enclosure components twice a week to compare with the construction documents. Performance testing of the installed enclosure systems included air/water infiltration testing and diagnostic nozzle testing of fenestrations to ensure the final product exceeded expectations.
Owner Houston Methodist Hospital System
Architect Page/ Contractor Vaughn Construction
Scope of Work Drawing Review, On-site QA/QC and Reporting, Commissioning of the Building Envelope, including Air Infiltration Testing per ASTM E783, Static Pressure Water Infiltration Testing per ASTM E1105, and Diagnostic Nozzle Water Testing per AAMA 501.2.
HEALTH EDUCATION CENTER
The construction of The University of Texas Medical Branch Health Education Center marks the first significant educational/academic building to be developed on the Galveston campus in almost 40 years. Zero/Six is currently providing preliminary construction documents, submittal, and RFI reviews pertaining to the exterior envelope to ensure an air and water tight facility and verify Texas Department of Insurance compliance with the design plans, the local Building Department and local building codes. Owner The University of Texas Medical Branch Architect EYP Architecture & Engineering (Rendering provided by EYP)
Contractor Vaughn Construction
Location Galveston, TX
Type New Construction
Scale 162,000 SF
Status Spring 2019
Cost $90.4 million
Scope of Work Drawing Review, On-site QA/QC and Reporting, TDI Windstorm Inspections and Certification, Sound Monitoring, and Commissioning of the Building Envelope, including Roof Membrane Uplift Resistance Testing per ASTM E907, Air Infiltration Testing per ASTM
E783, Static Pressure Water Infiltration Testing per ASTM E1105, and Diagnostic Nozzle Testing.
THE STORMWATER AUTHORITY DIVISION WAS ESTABLISHED TO MITIGATE THE DETRIMENTAL EFFECTS OF FLOOD & DESTRUCTIVE WATER
Z6 Commissioning recently announced the launch of Stormwater Authority, a new division that offers flood hazard analysis, levee management, and design, disaster recovery, dry floodproofing, wet floodproofing, as well as geotechnical engineering. Any doubts as to the vital importance of Stormwater Management would quickly evaporate after engaging in a conversation with anyone who experienced the effects of Hurricane Harvey first hand. Z6 Commissioning’s Stormwater Authority Division was established to mitigate the detrimental effects of flood and destructive water levels and surges. From small site-specific projects to county or regionwide assessments, Z6 Commissioning is the authority for all aspects of stormwater management.
Scott Leimer, P.E., an accomplished engineer, joins the firm’s new division as Vice President. He will lead the division’s tactical initiatives and help drive growth and develop new business opportunities, leveraging his extensive levee management experience and professional network
STORMWATER ENGINEERING & MANAGEMENT
WHAT IS STORMWATER ENGINEERING?
Stormwater Engineering is the evaluation of, planning for, and management of stormwater. This takes on many forms, ranging from single building flood proofing, to city and county drainage systems, to regional levee systems and dams. The planning of a successful stormwater engineering project involves close coordination by the project managers and design engineers with the owners/ operators/users of the facility. Proper project scoping and full project implementation are crucial for a successful project.
WHAT IS THE PURPOSE OF STORMWATER MANAGEMENT?
Stormwater management is necessary to provide risk reduction to life safety and property from rainfall or storm surge events. This is both the physical structure that conveys or constrains water along with the communication effort that addresses the likelihood and consequences of an event. Stormwater management should reduce the likelihood that flooding will occur to an acceptable level and communicate that likelihood to those that would be impacted should a flooding event occur.
WHAT TYPE OF STORMWATER STRUCTURES NEED TO HAVE MAINTENANCE AND CLEANING?
Stormwater management relies on a system of components functioning as designed and constructed. All of the components in the system must be operated and maintained in good working order for the system to perform as it is designed. Operation and maintenance, rehabilitation and replacement, along with total system assessment and reevaluation, should be conducted on a routine basis on all stormwater engineering projects.
INSPECTIONS CONDUCTED FOR FLOOD RISK AND LEVEE CONDITION ASSESSMENT.
Levee systems should have continuous inspections and condition assessments performed by the owners/operators. These condition assessments range from visual inspections to evaluate the physical condition of the levee system components, to full geotechnical and structural reevaluation to ensure the initial design and construction was adequate. Pumps, floodgates, drainage structures and other project features should also be reviewed and assessed routinely for operational adequacy.
WHAT DOES IT MEAN FOR A LEVEE TO BE CERTIFIED?
Levee certification is when an engineer or Federal agency completes an evaluation of the levee system and signs a statement stating that the levee complies with the applicable Federal requirements for design, construction, and operation and maintenance.
HOW DOES LEVEE CERTIFICATION DIFFER FROM LEVEE ACCREDITATION?
Levee certification is provided to FEMA by an outside party, whereas levee accreditation is an action that FEMA takes so the community living behind the levee system has National Flood Insurance Program (NFIP) benefits.
WHY IS IT IMPORTANT TO UNDERSTAND THE RISKS ASSOCIATED WITH LEVEES?
All levee systems have some risk associated with them. These risks can include potential overtopping, levee or floodwall failure, or excessive rainfall that exceeds the interior drainage capacity. Ultimately, levee systems are man-made structures that have design limitations. It is important to understand these limits so we can provide the necessary information to allow those who live within the levee system to develop a plan of action in the event those limits are exceeded to protect their community and property.
WHO IS RESPONSIBLE FOR BUILDING AND MAINTAINING LEVEES?
Levee design, construction, operations, and maintenance is not solely controlled by one entity; responsibility and ownership can vary from Federal, State, local or regional authority to private entities.
WHAT IS GEOTECHNICAL ENGINEERING?
Geotechnical engineering, for this discussion, is the study and evaluation of the surface and subsurface material for the design and construction of a structure. The structure could range from a building to a roadway, to a flood damage risk reduction feature, to a ship dock. The geotechnical engineer, through coordination with the project team, develops a soil investigation plan that defines the foundation requirements for the proposed structure.
WHAT DOES A TYPICAL GEOTECHNICAL SITE INSPECTION ENTAIL?
Geotechnical site inspections are conducted for a variety of reasons and the scope depends on the proposed project and the information that is needed. A site inspection for new construction would focus on defining any potential foundation issues and developing a plan for future subsurface investigations. An existing facility site investigation would focus on addressing any known issues and assessing the need and scope of any additional subsurface investigations.
HOW IS A GEOTECHNICAL INVESTIGATION CARRIED OUT?
Geotechnical investigations are carried out by utilizing a drill rig or other soil sampling methods to identify existing conditions and obtain samples around a site. The soil sample is then tested in
a laboratory to define and develop the physical and engineering properties of the soil for use by the design engineer. The generated data helps the engineer to understand the materials and properties that can influence the project requirements and determine the risks that may be created by existing site conditions.
WHAT LOCATIONS ARE MOST VULNERABLE IN THE TEXAS GULF COAST REGION?
The soil varies throughout a region due to the process in which it was deposited over the last tens of thousands of years; the main areas of concern tend to be in proximity to meandering streams, rivers, and coastal estuaries. These areas have more recent soil deposits that can create design and construction challenges.
WHAT ARE THE BENEFITS OF A GEOTECHNICAL REPORT?
The geotechnical report usually documents the subsurface soil profile, along with certain soil parameters and, if requested, foundation design recommendations. This allows the design engineer to properly characterize the subsurface soil conditions at the site, which is essential to having a successful project. Proper site characterization allows the design engineer to develop the most efficient foundation design, which will likely reduce project cost and construction time.
WHAT SHOULD A GEOTECHNICAL REPORT FOR COMMERCIAL DEVELOPMENT CONTAIN?
The information contained in the geotechnical report must be sufficient to ensure the successful construction and long-term utilization of the development. Coordination of the scope of the
geotechnical investigation with the designer of the development is a critical step in the overall execution of the project.
WHAT IS DISASTER RECOVERY?
Disaster recovery is a multi-step process that allows for the mitigation and recovery from damages due to a natural or manmade disaster.
WHAT IS THE IMPORTANCE OF A DISASTER RECOVERY PLAN?
Disaster recovery plans are extremely valuable to the owner and user of any facility. The disaster recovery plan allows concise action to be taken that can prevent, minimize, or reduce damages from occurring after a disaster.
In order to consolidate The University of Texas System operations from five antiquated buildings into one efficient location, the 19-story Replacement Office Building (ROB) and a parking garage were conceptualized for downtown Austin. This facility replaced a number of older university buildings and lease spaces, resulting in reduced maintenance and operating expenses. This created Class A offices for use by the UT System with three floors of shell space to be leased to non-UT System entities. Studies conducted by the university indicate the move will yield a total estimated net savings of more than $125 million over 30 years.
As the Building Envelope Commissioning (BECx) Agent for the project, Zero/Six prepared the BECx specifications, plan and testing requirements to support the basis of design, owner requirements,
and energy efficiency goals. Zero/Six conducted an extensive document review to identify deficiencies in systems integration and establish performance criteria for envelope assemblies; laboratory and field testing requirements were then developed to verify installation and functionality for an airtight and watertight enclosure upon completion. During the construction process, our inspectors conducted regular site visits to verify as-built systems were installed in accordance with the design intent while resolving any field issues to ensure an air and water-tight envelope is achieved.
Commissioning activities included functional performance testing, chamber tests, and roof uplift testing in accordance with ASTM standards, which allowed for timely correction during construction. After project completion, Zero/Six performed an infrared survey at the Level 20 roof of the building to ensure the owner received a roofing assembly free of moisture intrusion.
ONE POINT THAT IS OFTEN OVERLOOKED WITH REGARD TO BUILDING COMMISSIONING IS THAT IT’S AS MUCH OF A DESIGN VERIFICATION PROCESS AS IT IS A QUALITY ASSURANCE PROCESS.
In the 1800s, when a ship was commissioned by its captain it meant that it was deemed ready for service. This entailed passing several tests of the equipment, training its crew, and assuring a rigorous quality assurance process. Building commissioning takes the same approach to new buildings. When a building is commissioned it undergoes an intensive quality assurance process that begins during design and continues through construction, occupancy, and operations. In short, the commissioning process verifies that specific building systems perform in real life as we design and engineer them. Those of you who have participated in the construction of high performance, buildings are likely familiar with the term “commissioning,” even if you are not familiar with the commissioning process. Some of you may have been involved in these commissioning activities and did not even know it; activities such as peer reviews of construction documents and performance testing are not always labeled as commissioning activities per say, but they are in fact integral components to the commissioning process.
Historically, the commissioning process has been focused on mechanical, electrical, plumbing and IT systems; however, the past few years have found it more common to include the exterior building envelope in the commissioning process. This holds particularly true with regard to health care and research facilities. The bad news is that no one really seems to know how to scope the work for the envelope portion of the commissioning exercise. Most often it is added to the commissioning specification (typically a 12-page plus document) as one line that simply reads, “Commission the Exterior Envelope.” You can imagine the variety of proposals offered by those who undertake to commission the building envelope, but the good news is that as new trends emerge in the AEC industry, the innovators among us have the opportunity to influence its development. This article is my attempt at influencing that commissioning process.
Multiple reasons exist for the increasing popularity of envelope commissioning/consulting, but I believe that two major factors stand tall above all the others; the first is the vast amount of dispute resolution and litigation issues related to water infiltration. It really is immense and is comprised largely of new buildings that are less than five years old…and the owner/user is not happy. In fact, a very large portion of Zero/Six’s work is related to water infiltration on projects where final completion has yet to be achieved which testifies to the fact that owners have learned to become proactive in regards to water infiltration. Adding to the issue of water infiltration, the second issue is related to mechanical systems and the quality of the air they deliver. The building envelope is the ultimate building plenum (duct). Just as the efficiency of an HVAC system is dependent on an airtight plenum, the ability of the sub-systems within the envelope to perform as designed is directly related to the tightness of the exterior building envelope. An effective building envelope commissioning process must address these two issues through a three-step process designed to fulfill the commissioning process
Develop the Intent
One point that is often overlooked with regard to building commissioning is that it’s as much of a design verification process as it is a quality assurance process. In the traditional MEP/IT commissioning process, the commissioning agent is placed on the project team very early in the process to provide input during the design phase. The intent is to gain assurance during the design phase so that when the building is constructed it performs as specified. Generally speaking, MEP/ IT systems remain fairly constant from building type to building type and their installation is closely dictated by code which results in a performance criterion that can be accurately forecasted. The building envelope, on the other hand, has to be restudied for each project due to the unique architecture design associated with each
new building. Since “design” is fluid and likely to change, it is equally important that the envelope commissioning begins at the early stages along with MEP/IT. Think about it: if a pump, switch, or air handler do not perform, they can be replaced. However, if a flashing is overlooked in the design phase, portions of the cladding may have to be removed to install it later. Then, consider that the same flashing might have been left out at every window of an occupied high-rise structure and now you have a remedial project that will require significant time and funding once the oversight becomes apparent to all within. Been there, done that.
One of the goals of the envelope commissioning process is to participate in the design process and address details before they become an issue. Mock-ups are a vital part of the process when attempting to “Develop the Intent.” Because building Architecture varies from project to project, mock-ups of the project specific conditions become invaluable prototypes. Although cladding systems often are repeated among various projects, their relationship to adjacent systems is always changing. With the evolution of Building Information Modeling (BIM), many of these mock-ups can be generated inexpensively on a virtual platform; for testing purposes though, there is no substitute for a full-size working mock-up.
Inspect the Product
Assuming that you now have construction documents that convey the intent, the next step in the commissioning process is to “Inspect the Product” through a quality control (QC) program executed by persons who understand how the various systems will interface. This person must also be able to go beyond understanding the systems interface as the success of the QC program is largely dependent on the ability of the inspector to safely access hard to reach areas regularly. Finally, as part of the QC program, deficient work is logged as it’s observed and then tracked to a resolution; in other words, no “punch list surprises” at substantial completion.
Test the Collaborative Effort
Successful building construction depends on the successful collaboration of designers, manufacturers, and installers. Because testing verifies design as well as construction, the collaborative effort must be tested early in the process so repetitive deficiencies can be corrected prior to a full-blown remediation effort.
Testing commonly included in the commissioning process:
• Flood testing of below grade areas and water-proofed
• Pull testing of sealant joints
• Water infiltration testing of windows per ASTM E1105
• Roof uplift testing per ASTM E907
• Thermal imaging of building envelope
It’s true that expanding the commissioning process as it relates to the exterior building envelope is an additional “line item” in the project estimate, but I would argue that it does not add to the bottom line of the total project cost. Projects that do not address envelope issues up front often times end up addressing them near substantial completion due to failed testing. The cost associated with recovery programs typically dwarf the cost associated with an envelope commissioning program. Consider the following case study as an example, and keep in mind that this is not unique in this industry:
A high rise tower project that involved Zero/Six included over 1600 shop fabricated high performance punched windows in pre-cast concrete openings. In an effort to provide better quality control of the fabricated units, the window contractor elected to fabricate these units off-site in their shop environment. The project team included a premier Architect, a first-class construction team, a first-class product, and the world’s easiest window installation detail. No problem, right? Wrong.
Somewhere between the shop and the project site, 200 miles away, the units were ever so slightly damaged, resulting in water infiltration during rain events. I suspect that the damage was related to shipping and/or crating due to the consistent nature of this defect. The lesson learned from this story is that a commissioning program would have included testing windows early on and would have established a recovery plan that was proactive and did not involve the postmortem removal of 1600 windows over a three month period.
In closing, the whole building commissioning process is an invaluable tool for the entire project team. Potential performance issues can be identified and addressed during the design phase, thus defusing construction defect based claims where mediation finds everyone writing checks. Additionally, building performance is well documented at building delivery, so if the building is found not to perform at some point in the future; it may be related to post construction issues such as maintenance. Not that it ever happens… I’m just sayin’.
The Ango Global Headquarters Building is an 18,530-square-foot office that was built for an Angolan oil company. This building features extremely high-end finishes and includes structural studs, masonry exterior walls, and extensive glass curtain walls. Ango Global commissioned Zero/Six to perform an exterior envelope assessment in an effort to ascertain the overall condition of the building’s ability to resist water infiltration.
Owner: Ango Global International, Inc.
Contractor: Arch-Con Corporation
Location: Sugar Land, TX
Scale: 18,500 SF
Scope of Work: Exterior Envelope Forensic Assessment
The Post Oak School is a Montessori school with two campuses in Greater Houston. Zero/Six provided professional services related to the concrete roof tile replacement for the Bissonnet campus, which will be dedicated solely to early childhood development and elementary education programs. Our team produced construction drawings, coordinated the bidding process and performed on-site QA/QC and reporting services during the construction phase of the first large-scale renovation and expansion in 15 years for the school.
Owner: The Post Oak School
Location: Bellaire, TX
Type: Renovation & Expansion
Scope of Work: Site Survey Investigation, Preparation of Specifications and Construction Documents, Bidding Process, QA/QC Roof Replacement Monitoring, and Construction Administration
St. Mary Cathedral Basilica is a Gothic Revival church designed by Paris trained Architect Theodore E. Giraud. The floor plan is a traditional Latin cross with the entrance facing west. The masonry mass wall and timber-framed structure include 500,000 Belgium bricks that had been used for shipping ballast. In 1876, a bell tower, designed by Architect Nicholas Clayton, was added to the east side of the cathedral, and in 1878, a cast-iron statue of “Mary Star of the Sea” was added to the top of the bell tower. In 1884, Clayton raised the twin spires on the west side of the cathedral to eighty feet, an elevation just below that of the bell tower. On August 2, 1979, Pope John Paul II made St. Mary’s Cathedral a minor basilica in recognition of its historical importance. Zero/Six performed an assessment of the exterior building envelope, providing a report outlining findings, suggested next steps, and repair recommendations.
Owner: Archdiocese of Galveston-Houston
Location: Galveston, TX
Year Built: 1848
Scope of Work: Exterior Envelope Forensic Assessment
The state-of-the-art facility boasts flexible classrooms, student project laboratories, and new research space that facilitates advanced teaching techniques to bring together students, faculty, and researchers to redefine engineering education for the 21st century. Totaling over 400,000-square-feet (sq. ft.), the modern, open-concept facility is the Cockrell School’s largest multidisciplinary building. The effect of which increased enrollment by 1,000 students to a total of more than 6,000, as well as increased the number of innovative engineering faculty members that collaborate to solve critical challenges within the industry.
In April 2015, Zero/Six Consulting collaborated with The University of Texas System and Hensel Phelps Construction Co. to assemble the components in a BIM framework to coordinate shop drawings for the 432,671 sq. ft. facility. Numerous architectural and structural drawings multiplied the potential for discrepancies both before and after construction. Imagine putting together a puzzle with pieces
designed by ten different companies. The building envelope process is like that puzzle; consisting of a collective of multiple design components coming together for the first time on-site. Building Information Modeling (BIM) puts all the pieces together virtually so that multiple design elements come together on-site with identified design mistakes and oversights corrected prior to construction. By combining the envelope drawings and structural model into an intelligent 3D design, Zero /Six was able to identify issues that would have been costly to remedy once the pieces came together on-site.
“To the best of our knowledge, nobody has ever attempted to create a composite envelope BIM model,” said Bill Coltzer Jr., AIA, President at Zero /Six. “So, in April, we found ourselves sitting in an exterior envelope pre-construction meeting for the new EERC building; when they asked who could create a Composite Building Envelope BIM Model, we raised our hand. Originally this document was intended to be a virtual clash detection tool that would find issues. As the process evolved and the lack of cohesiveness in assembling components together became evident, we switched gears and instead provided Hensel Phelps a large change order that was ultimately the basis of construction for the entire exterior envelope. In the end, this was much more convenient for the construction team because they were able to spend more time managing construction and much less time sending the architect RFI’s,” added Coltzer.
For the process to work well there must be a collaboration between the coordinating party, BIM operators, subcontractors, and the design team. The firm would not have been able to successfully
coordinate the EERC project if we did not receive feedback from the subcontractors. To model certain components so they fit into the virtual envelope assembly, Zero /Six (or any coordinating team)
needs to know what the subcontractor has the ability to manufacture. For example, while coordinating the limestone masonry units on the EERC, the masonry subcontractor informed us that while the stone
pattern appears random, there are only 3 primary stone widths on the building façade. Had Zero /Six altered the stone to make more room for other components, the price of manufacturing and installing the stone would have increased significantly. Without participation from all parties, the coordination effort would not have been a success.
The University of Texas EERC project was not a pain-free job; however, many of the potential construction errors were avoided by using BIM coordination tools and subcontractor collaboration.
Through collaboration, Zero/Six was able to proactively approach both shop fabrication and on-site production. For example, the EERC used unitized curtain wall systems almost exclusively. These
systems arrive on-site pre-manufactured and cannot be modified. There was a condition on the project where there were numerous unitized curtain walls above a modified bitumen roof curb. The shop
drawings provided by the curtain wall contractor showed the curtain wall sitting directly on the roof system with insufficient clearance to terminate the roof edge with a counter flashing. By using BIM
in our envelope consulting to virtually construct the project, Zero/Six was able to identify the issue, propose a solution, and bring the contractors together so that a revision to the shop drawings could
be made prior to installation in the field. Though BIM is not a new technology, the process of integrating BIM technology into the construction phase is a critical step that should be incorporated in the future so that issues are identified virtually within the composite model before becoming a reality on the construction site.
Specifying types of polymer modified bitumen (MB) membrane reinforcement can play a large role in the performance and life of a roof system. There are multiple factors to consider before specifying a type of roof membrane, such as geographical location. In Texas, we have extreme heat and hurricane force winds which can shorten the lifespan of the roof. The addition of a few keywords to the specification, like “composite,” “woven mat,” or “scrim reinforcement,” can improve the longevity and performance level of the roof system by 20-40% beyond the ASTM standards. The American Society for Testing and Materials (ASTM) is the organization that sets the standards to define the specific types of reinforcement materials. ASTM’s standards should be viewed as having the minimal code requirements for construction. These standards create a foundation for the roof system but don’t provide the upgrades that can provide enhanced durability and or extended life cycle expectancy. ASTM relies on qualified members from around the world to develop the standards, but the organization does not have an in-house testing facility or technical research center for material testing, so it uses accredited facilities like the Z6 Commissioning laboratory to help develop them. These standards provide dimensional tolerances, physical properties, performance requirements and material appearance requirements.
The MB roof system standards are drafted and reviewed by industry professionals and manufacturer’s representatives for approval, then published if a two-thirds consensus is achieved. There are five typical ASTM standards used to define the structural performance characteristics of a styrene butadiene styrene (SBS) or atactic polypropylene (APP) MB membrane. There are three commonly used polymer modified roofing material standards for SBS by ASTM. These standards define reinforcement types using glass fiber (ASTM 6163), polyester (ASTM 6164), or combination (ASTM 6162). There are two standards which define reinforcements for APP polyester (ASTM 6222) or a combination of polyester and glass fiber (ASTM 6223). These standards are further defined with type classifications I, II, and III, differentiated by increasing weights and area of sheet per unit. The grade of the unit is distinguished with a granule-surface (G) or smooth surfaced (S) materials. An example of ASTM D6162, Type I or II, Grade S in the specification reads, “Standard Specification for Styrene Butadiene Styrene (SBS) Modified Bituminous Sheet Materials Using a Combination of Polyester and Glass Fiber Reinforcements.” There are no additional distinctions defined in these standards to specify a type of fabric used for reinforcements.
The words scrim or non-woven (i.e. mat) are left out of the standards. SBS is a plastomer with elasticity characteristics that have consistent properties throughout a wide temperature range. The SBS will stay flexible even in cold temperatures below 32° F. SBS has a melting point of 210° F which allows a variety of application methods. SBS membranes can be cold applied, hot mopped, or propane torch applied. APP MBs tend to be stronger and stiffer and will provide greater resistance to high temperatures. APP MBs are typically only applied via propane torching with a melting point of 300°F or through cold applied polymer-modified adhesives. Specifying a scrim or composite in either APP or SBS will lead to a superior product line for just about any manufacturer.
The performance criteria to consider when choosing a membrane combination are watertight laps, blister resistance, resistance to splitting, delamination resistance, shrinkage resistance, and durability. Reinforcing materials of the MBs will serve as the carrier for the polymers and will work as a structural element to bridge substrate joints. The combinations of materials will then increase tensile strength, puncture resistance, and provide increased fire protection.
There are two main types of reinforcement fabrics – scrims and fabric mats. Scrims are fabrics woven together in both machine and cross machine directions and are used in high-performance membranes, providing a greater tensile and tear strength than minimum ASTM standards. Fabric mats are non-woven (unless specified as “woven mat”) comprised of randomly distributed fibers which are dependent on binders achieved through chemical adhesives, thermally, or mechanically. They typically have an overlapping arrangement and have less resistance to tensile and tear strength. Composites or laminates include both scrim and mats which are chemically or mechanically bonded. Composites will typically combine characteristics for superior tensile strength and puncture resistance. Glass fibers are more dimensionally stable and more heat resistant than polyester fibers. Glass fibers will not break down with ultraviolet (UV) exposure but polyester will. Polyester, however, has greater resistance to puncture, strain energy, and flexibility. Since polyester and fiberglass are complementary, the best approach is a two-ply membrane minimum incorporating both materials.
The placement and type of reinforcements can have a significant effect on the weathering characteristics of the finished roof membranes. Studies* have shown that the use of polyester mats, due to their dimensional instability, in cap membrane of both APP and SBS can accelerate the natural weathering causing cracking and crazing, which is a network of fine cracks on the surface of the material. The best-performing systems have an inner ply and cap membranes to incorporate both a scrim and a mat. Failures can occur with systems using only scrims due to excessive dimensional instability which can lead to failures with the membrane splitting. The use of only nonwoven mats can cause a less dimensionally stable reinforcement that can eventually result in stress to the seams due to shrinkage.
In the harsh environment of the Texas coastal region, there is little room to accept only the minimum criteria where every manufacturer meets the benchmark. Relying only on the standards can be shortsighted which tends to damage the health of the modified bitumen industry. This is evident due to the fact that so many roof systems are compromised by water infiltration, cutting their lifespans short before the warranty is over. Referencing reinforcement fabric type combinations in the specifications can provide a healthy boost in performance and durability for the roof system. *Source: Baxter, Richard and Tim Keamney, “Weathering.