s designers and building own­ moisture-storage capacity. Additionally, the and associated framing. All these factors ers place increased demands drying efficiency of uninsulated mass-ma­ make rapid drainage and drying of exterior on exterior walls to isolate the sonry walls is aided by the passage of inte­ wall systems even more vital. outside climate from the inte­ rior energy out through the mass (Figure 1). rior controlled environment, Today, thick mass masonry walls have CAVITY WALL TYPES exterior walls’ capability to been replaced with thin, energy-efficient Today there are three main types of cav­ Aprovide long-term assured performance and economical masonry cavity wall con­ ity wall design: must grow. As building enclosure design struction with internal water and air bar­ • Unventilated evolves, it is becoming more evident that riers, continuous insulation, and air space • Pressure-equalized important attributes of durable exterior cav­ between the structural support wall and the • Ventilated ity walls, in wet climates, must include the exterior veneer (Figure 2). This modern wall ability of the exterior wall to drain and dry assembly has isolated the veneer to expe­ UNVENTILATED CAVITY WALLS quickly to protect the wall assembly from rience more thermal and material move­ The roots of modern cavity wall design moisture-related issues. ment, moisture-related stresses, and stain­ can be traced back to the late 1800s, when ing potential than massive masonry walls. wall systems started to become less massive, CAVITY WALL EVOLUTION Adding to the challenge of designing dura­ due to better material strength, improved Historically, exterior masonry walls ble exterior wall managed water by utilizing an abundance systems, structural Figure 2 – Modern masonry cavity wall of mass to absorb moisture from the envi­ masonry support detail from International Masonry Institute’s ronment and then release it back slowly by walls are some­ Masonry Detailing series, www.imiweb.org. random drainage and evaporation when the times replaced with exterior relative humidity allowed. Typically, moisture-sensitive bulk water did not reach interior surfaces of materials such as thick mass walls due to the multiple mason­ wood and other ry wythes, each with their inherent high sheathing products No one wants to lose products or reputation because of reroofing dust and debris. Protect yourself and your clients by doing it right the first time with SmartSeam® installed by TuffWrap®. It is theonly Suspended Cover product that is UL listed and classified to UL 723s for installation below fire sprinklers. Our antimicrobial, antistatic and flame retardant material has a heat reactive seam that breaks away during a fire, preventing sprinkler system impairment. This means you can have the Suspended Cover solution you know and trust without compromising on safety. Avoid do-overs and learn more at www.tuffwrap.com/protection or by calling 800.995.4556! Figure 1 – Example of a mass masonry wall from the late 19th century. M A R C H 2 0 1 6 I N T E R F A C E • 2 3 TuffWrap and SmartSeam are registered trademarks of TuffWrap Installations, Inc. ity walls, in wet climates, must include the to experience more thermal and material ability of the exterior wall to drain and dry movement, moisture-related stresses, and quickly to protect the wall assembly from staining potential than massive masonry moisture-related issues. walls. Adding to the challenge of designing durable exterior wall systems, structur­ CAVITY WALL EVOLUTION al masonry support walls are sometimes Historically, exterior masonry walls replaced with moisture-sensitive materials managed water by utilizing an abundance such as wood and other sheathing products of mass to absorb moisture from the envi­ and associated framing. All these factors ronment and then release it back slowly by make rapid drainage and drying of exterior random drainage and evaporation when the wall systems even more vital. exterior relative humidity allowed. Typically, bulk water did not reach interior surfaces of CAVITY WALL TYPES thick mass walls due to the multiple mason­ Today there are three main types of cav­ ry wythes, each with their inherent high ity wall design: Figure 3 – Example of early cavity wall moisture-storage capacity. Additionally, the • Unventilated design from 1894. drying efficiency of uninsulated mass-ma­ • Pressure-equalized s designers and building own­ sonry walls is aided by the passage of inte­ • Ventilated ers place increased demands rior energy out through the mass (Figure 1). on exterior walls to isolate the Today, thick mass masonry walls have UNVENTILATED CAVITY WALLS outside climate from the inte­ been replaced with thin, energy-efficient The roots of modern cavity wall design rior controlled environment, and economical masonry cavity wall con­ can be traced back to the late 1800s, when exterior walls’ capability to struction with internal water and air bar­ wall systems started to become less massive, Aprovide long-term assured performance riers, continuous insulation, and air space due to better material strength, improved must grow. As building enclosure design between the structural support wall and understanding of the system, and a desire evolves, it is becoming more evident that the exterior veneer (Figure 2). This mod­ to reduce material cost, increase speed of important attributes of durable exterior cav­ ern wall assembly has isolated the veneer construction, and minimize thermal and Trinity|ERD is pleased to announce the opening of its new wind testing laboratory in Oxford, CT, the latest expansion of its service offering. Having conducted static uplift testing of commercial roofing systems for over 20 years, Trinity|ERD now offers customers testing to the CAN/CSA A123.21 dynamic wind uplift resistance standard, which is the only codified wind uplift standard in the National Building Code of Canada (NBCC 2015). One of two ISO 17025 accredited (IAS TL-689) laboratories in the world using equipment commissioned through the National Research Council of Canada (NRC). 12x24 ft chamber size to mirror historical static testing. Criticality analysis for selection of critical components. ISO 17025 accredited for static wind uplift standards codified in the International Building Code and Florida Building Code. ANSI/FM Standard 4474 UL 1897 Florida HVHZ TAS 114, Appendix D & J ISO 17025 accredited for field (in-situ) static wind uplift standards. ANSI/SPRI IA-1 ASTM E907 FM Loss Prevention Data Sheet 1-52 Florida HVHZ TAS 124 353 Christian Street, Unit 13 Oxford, Connecticut 06478 Phone: 203-262-9245 [email protected] 2 4 • I N T E R F A C e M A R C H 2 0 1 6 moisture transfer across the wall (Figure Figure 4 – Diagram showing 3). For nearly 100 years, unventilated cav­ the two purposes of weep ity walls were the norm until the mid to vents: 1) to allow moisture out late 1900s, when building designers start­ of the wall, and 2) to allow ed to experiment with alternative design air into the wall cavity. This strategies to refine moisture, staining, and diagram shows airflow in energy management methods for cavity one direction, but it could be walls by introducing upgraded wall assem­ reversed or neutral, depending bly components and advanced moisture on environmental condition control design strategies such as pressure- and building configuration. Air equalized rainscreen wall concepts. control is recommended on the support wall when allowing exterior air into the wall cavity. PRESSURE-EQUALIZED CAVITY WALLS In theory, pressure-equalized rainscreen walls are designed to allow enough exterior air into the wall cavity to create backpres­ sure to reduce or eliminate the positive force of wind-driven rain against the veneer. However, in reality, there are too many variables required in order for a system to be designed and installed flawlessly and achieve a true net-zero pressure differential across a veneer. To achieve a pressure- equalized rainscreen wall, the wall design What’s up? needs to address: • The rigidity of the support wall Hopefully , your pipes are. Code says they must be raised up from the roof. • Actual air barrier continuity and MAPA offers an extensive line of innovative, long-lasting roof supports that tightness • The weep vent type/spacing/loca­ add years to the life of a roof. Do it the right way. The MAPA way. tion in the wall n Highest quality materials DUT • A weep-vent-free area of venting RD Y n Allows pipes to expand and contract DA • Increased modern air space recom­ N without abrading roof A Single post mendations T n Quick height adjustment S support • Wall cavity baffle airtightness n Integrated, reinforced base pads protect roof For condensate or • Mortar droppings sloped lines • Landscaping mulch n Ships fully assembled • Overall workmanship n Complies with International Fuel Gas Code, MSS-58, MSS-69 and MSS-127 Pressure-equalized rainscreen walls can be achieved, but not without proper calcu­ lations, design, quality control, instrumen­ Roller support tal verification, and skilled craftworkers. For gas and Innovative rooftop supports since 1998 mechanical lines Because of the complexity of pressure- www.mapaproducts.com equalized rainscreen walls and the high level of wall assembly coordination required, it is ideal to have one contractor install TY the entire exterior wall assembly for sin­ DU Y gle-source responsibility. V A E VENTILATED CAVITY WALLS H A more realistic and economical Strut support approach for increased moisture manage­ For conduit or ment in exterior cavity walls is the use of refrigeration lines a ventilated cavity wall concept. Ventilated cavity walls use some similar components of pressure-equalized rainscreen walls, but Trapeze support without the calculations, small air space For heavy duty and duct applications chamber requirements, observation, test­ ing, and related cost. In fact, some building M A R C H 2 0 1 6 I N T E R F A C E • 2 7 scientists have stated that many, if not most, pressure-equalized rainscreen walls are not properly designed or executed and are just functioning as “well-ventilated cav­ ity walls,” anyway.