Retrofitting Exterior Wall Assemblies With Rainscreen Systems Neil W. Garry, RRC, PE Bell & Spina, Architects-Planners, PC 215 Wyoming Street, Suite 201, Syracuse, NY 13204 Phone: 585-200-5038 • 585-248-9532 • E-mail: ngarry@bellandspina.com 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 G a rr y • 1 8 9 Abstract Many commercial and institutional buildings constructed in the 20th century feature wall assemblies with underperforming or nonexistent air barriers, drainage planes, and insulation planes. Rainscreen technologies offer the possibility of improving the performance of these walls while simultaneously modernizing the appearance of their retrofitted façades. Design considerations and limitations will be reviewed for specifying and constructing rainscreen systems in retrofit applications. The need for North American rainscreen design and performance standards will be discussed. A synopsis of related European standards will be presented and their adaptability for use considered. Speaker Neil W. Garry, RRC, PE – Bell and Spina, Architects-Planners, PC Neil W. Garr y is a partner at the Rochester, New York, office of Bell and Spina, Architects-Planners. Much of his 15-year professional career has focused on the technical aspects of building envelope systems. He is a licensed structural engineer, a Registered Roof Consultant, and a member of ASTM International Technical Committee DO8, Roofing and Waterproofing; and Committee E06, Performance of Buildings. 1 9 0 • Ga rr y 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 INTRODUCTION Many commercial and institutional buildings constructed in the 20th Century feature wall assemblies with underperforming or nonexistent air barriers, drainage planes, and insulation planes. Rainscreen technologies offer the possibility of improving the performance of these walls while simultaneously modernizing the appearance of their retrofitted façades. DEFINING RAINSCREEN SYSTEMS The Rainscreen Principle In her book, Designing the Exterior Wall, Linda Brock put it best when she wrote, “A rainscreen means different things to different people.” Very competent design professionals, consultants, contractors, and building product manufacturers will offer a wide variety of responses when asked, “What is a rainscreen?” At its essence, the rainscreen principle involves the “screening” or limiting of water entry at an exterior wall through use of a primary, exterior control barrier. Any water that potentially penetrates the exterior is controlled by a secondary inner barrier, isolated from the primary barrier by an air space. This inner plane typically features a water-resistive barrier (WRB), often doubling as an air barrier, as well as insulation and structural components. When viewed so generically, it is little wonder that any wall with a veneer and drainage plane is often coined a “rainscreen” wall. It is sometimes ascribed to residential clapboards installed on furring strips. It is at other times ascribed to conventional, unvented masonry cavity walls. In the experience of the author, most design professionals envision an assembly far more design-intensive but offering a broad palette of technical and aesthetic options. In an effort to more succinctly differentiate rainscreen walls from other wall types, the Metal Construction Association released a publication in 2006 entitled, “Understanding the Rainscreen Principle.” It advocates definitions for two rainscreen types: drained/back-ventilated systems (DBV) and pressure-equalized/compartmentalized systems (PER). Back-Ventilated Rainscreen A DBV rainscreen system (Figure 1) features an exterior control plane and/or cladding panels with open joints designed to accommodate differentials in pressure between the exterior air and that behind the cladding. These dissimilar pressures result in the occasional introduction of water at the secondary, inner control plane. Insulation positioned between the two needs, therefore, to be water-resistant. The continuity of the WRB/air barrier is critical to directing water back out of the system, controlling the migration of air through the wall, and limiting the inner boundary of air behind the cladding. In North America, most rainscreen walls in service today are arguably DBV systems. Pressure-Equalized Rainscreen A PER system (Figure 2) features an exterior control barrier and/or cladding panels with open joints, designed to equalize pressure between the exterior air and that behind the cladding. These equalized pressures deter water sheeting along the face of the barrier from entering the joints. This is accomplished through the introduction of rigid, compartmentalized air chambers between the cladding and air barrier, coupled with control of the panel joint sizes and configurations. “Construction Technology Update No. 17, Pressure Equalization in Rainscreen Wall Systems,” was published by the National Research Council of Canada in 1998 and has served as a common reference in North America for determining volume/ venting ratios for PER systems. Unlike DBV systems, where air moves relatively undeterred behind the expanse of cladding, PER systems endeavor to confine the air and control displacement. The two systems are otherwise similar. Evaluating System Effectiveness The American Architectural Manufacturers’ Association (AAMA) has developed two tests to evaluate the effectiveness of DVB and PER systems. The first is known as AAMA 508-07, “Voluntary Test Method and Specification for Pressure-Equalized Retrofitting Exterior Wall Assemblies With Rainscreen Systems 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 G a rr y • 1 9 1 Figure 1 – Drained/back-ventilated rainscreen. Figure 2 – Pressure-equalized rainscreen. Rainscreen Wall Cladding Systems.” This is a laboratory mock-up test to determine the extent to which water will accumulate on a WRB and confirm the effectiveness of the tested pressure-equalization system. The second test is known as AAMA 508-09, “Voluntary Test and Classification Method of Drained and Back-Ventilated Rainscreen Wall Cladding Systems.” This is a laboratory mock-up test to determine the water resistance and ventilation capacity of a specimen DBV system. As their names imply, these tests are voluntary. Their use to date in project specifications appears to be somewhat limited, possibly due to the costs associated with conducting these tests for the many permutations of conceivable rainscreen assemblies. Rainscreen Advantages The two defined rainscreen systems require no mortar or sealants. Because joint treatments do not exist, their maintenance is far less demanding. Further, the selection of panel products available enables appealing variety in the design of façades. With the arguable exception of their attachments, rainscreen systems invite wall components to be optimally positioned for energy performance. For example, since the cladding panels are secured over the insulation and do not rely on a bearing surface for support, the insulation plane can envelop the structure in alignment with the foundation face and easily extended below grade. In cold climates, if the WRB also serves as an air barrier and vapor retarder, it can be positioned behind the insulation and extended to interface with the roof vapor retarder and foundation waterproofing. These advantages are particularly appealing when retrofitting a solid masonry wall because installation of these components can be accomplished from the building exterior with minimal disturbance to the occupants. RAINSCREEN MATERIALS North American Market DVB and PER systems have seen relatively longer service in Europe; consequently, many rainscreen products used in North America today are produced by European manufacturers. Such products are typically manufactured to SI Unit tolerances, which vary, depending on the standards of the country in which they were produced. If using panels not readily altered in the field, not all manufacturers are willing to produce panels varying from their standard dimensions. This can pose challenges both in specifying competitive systems and interfacing components with North American products fabricated and/or built to Imperial Units. The latter is particularly true when interfacing rainscreen panels with North American window/door units, aligning panels vertically with masonry coursing, and coordinating the horizontal panel layout with the overall length of the building. Special care must, therefore, be taken when using European panels to ensure that dimensional differences are considered in the design. Another important consideration is the matter of rainscreen system delivery. Some manufacturers prefer only to supply panels, which leaves the supply of the underlying support grillage and fasteners to others. The engineering of such components is undertaken by the A/E of record, subcontracted to a consulting engineer, or delegated to an engineer retained by the supplier or installer. A market has therefore arisen for support grillage designers and suppliers working with a variety of panel products, each with unique properties, attaching to various substrates with components obtained from numerous sources. While material standards exist for some of these components, there are limited industry design standards for complete rainscreen systems. These parties therefore rely heavily on their own experience and engineering judgment. The alternative approach taken by some panel manufacturers is to supply both the panels and the support grillage, in which case they alone are orchestrating the previously described activities. They occasionally validate their designs with European assembly technical approvals, such as those issued by the Centre Scientifique et Technique du Batiment (Secretariat of the Technical Approval Commission or CSTB). In either case, the A/E of record must specify the locations, extent, and performance requirements of the rainscreen assembly components, as well as the selected panel material. Metal Panels Metal rainscreen panels enjoy the favorable advantage of being commonly manufactured in North America. They are available in most any architectural metal and can be fabricated as plate, sheet, or formed metal—depending on strength requirements. They are subject to relatively high rates of thermal expansion/contraction that must be accommodated in the design. Numerous ASTM standards exist for materials used in metal panel systems, as well as certain structural and system performance standards derived from the metal roofing industry. Thin, Nonmetallic Panels Thin, nonmetallic panels enjoy the advantage of being readily modified or fabricated in the field. These include wood, fiber cement, fiber-reinforced plastics, and high-pressure laminates (HPL). Some of these products require surface treatments, particularly at cut edges. The majority of these systems tend to be through-fastened, although some are available with sliding clip attachments. In addition to publishing rates of thermal expansion/contraction, manufacturers of many of these products also publish data regarding moisture-related dimensional stability. Panels in this category are often tested and measured to European, EN standards—not always corresponding with comparable ASTM standards. Thick, Nonmetallic Panels Thick, nonmetallic panels tend to be noted for the advantages of visual warmth and durability. These include terra cotta, porcelain stone, concrete, and natural stone—in all cases without the sealed joints of their barrier wall counterparts. While thinner versions are available, these panels tend to be heavy. Many have characteristically long lead times for material deliveries, particularly those that are quarried and/ or manufactured in Europe. The attachments are typically concealed, sliding clips. Some critical tolerances for these products are moisture absorption, freeze-thaw resistance, thickness, height, length, orthogonal alignment, straightness, and flatness. However, these tolerances tend to vary among manufacturers of comparable panels. In the absence of consensus, the A/E of record must carefully consider the panel tolerances suitable for the project and research the extent to which prospective suppliers will be able to meet them. Vented Brick It is important to note that both DBV and PER principles can be applied to vented brick veneers, which are not to be con- 1 9 2 • Ga rr y 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 fused with conventional brick cavity walls. Guidelines for the design of such systems can be found in “BIA Technical Notes 27 – Brick Masonry Rainscreen Walls.” EVALUATION OF EXISTING EXTERIOR-WALL ASSEMBLIES FOR RETROFIT There are a number of conditions that can prompt consideration of retrofitting an exterior wall with a rainscreen assembly. These include deficiencies of insulation, air barriers, and veneer construction. One very compelling incentive is the need to improve such deficiencies while the building remains occupied. USE & OCCUPANCY Access When considering the perimeter wall as part of the overall building/user interface, one has an opportunity to potentially enhance, define, or even redefine the building entrances and exits. Improvements can be made to egress, ADA compliance, security, and overhead sun/rain/snow/ice protection. Façade retrofit schemes can often accommodate the introduction of canopies and awnings. Construction Phase Occupancy If the building is to remain occupied throughout the course of a façade retrofit project, building entrances and egresses will need to remain operational and protected. If doors and windows are to be replaced as part of the project, some minimal disturbance to the building occupants should be anticipated. As such, a phasing plan should be developed for the occupants wherein swing space is made available to those temporarily affected by replacement operations. Considerations might also be required for temporary security measures while windows and doors are being replaced. Maintenance The building owner will need to be able to maintain the installed rainscreen assembly. As such, consideration should be given to the durability and ease of repair for any given panel system. Panel returns should be designed in such a way that they need not be removed to facilitate future replacement of doors and windows. Some systems may require the introduction of strategically placed metal closures to limit insect entry. Neighborhood It is good practice to consider the proposed appearance of the building in the context of the surrounding environs. While this does not imply a need for draconian repetition, the retrofitted façade should at least complement its setting. STRUCTURE Dangerous Condition (IBC) A structural evaluation must be made of the existing wall assembly by a registered design professional. The physical condition of the wall should be assessed to determine which components are serviceable and/or salvageable. Up to and including the 2006 version of the International Building Code (IBC), Section 202 clearly defined the minimum traits of a “dangerous condition.” DANGEROUS. Any building or structure or any individual member with any of the structural conditions or defects described below shall be deemed dangerous: 1. The stress in a member or portion thereof due to all factored dead and live loads is more than one and one third the nominal strength allowed in the International Building Code for new buildings of similar structure, purpose, or location. 2. Any portion, member, or appurtenance thereof is likely to fail, or to become detached or dislodged, or to collapse and thereby injure persons. 3. Any portion of a building, or any member, appurtenance, or ornamentation on the exterior thereof is not of sufficient strength or stability, or is not anchored, attached, or fastened in place so as to be capable of resisting a wind pressure of two thirds of that specified in the International Building Code for new buildings of similar structure, purpose, or location without exceeding the nominal strength permitted in the International Building Code for such buildings 4. The building, or any portion thereof, is likely to collapse partially or completely because of dilapidation, deterioration or decay; construction in violation of the International Building Code; the removal, movement, or instability of any portion of the ground necessary for the purpose of supporting such building; the deterioration, decay, or inadequacy of its foundation; damage due to fire, earthquake, wind, or flood; or any other similar cause 5. The exterior walls or other vertical structural members list, lean, or buckle to such an extent that a plumb line passing through the center of gravity does not fall inside the middle one third of the base. This definition is contained in many codes throughout the United States and serves as a minimum basis of evaluation. Wind Loading (ASCE 7) If considering retrofit with a rainscreen assembly, it must be capable of sustaining the full “components and cladding” design wind loading prescribed by code, which often references ASCE 7. The capacity of the existing wall structure to receive these loads from the rainscreen must also be considered. The reduction of wind design loads in the presence of a PER assembly is not recommended. Cladding Support The existing wall structure must be capable of sustaining all design loads, including those imparted by and on the prospective rainscreen assembly. Because it is typically mounted to the face of the wall structure and not supported by a bearing shelf, a rainscreen system will impart an eccentric gravity load to the wall, increasing both flexure in the wall span and shear at its upper and lower supports (Figure 3). When evaluated with wind or seismic loading, the fasteners that connect the rain- 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 G a rr y • 1 9 3 Figure 3 – Eccentric gravity loading. screen assembly to the wall structure will be subject to combined shear and tension. For retrofit applications, pull tests can be made of the prospective fasteners in the field to confirm their ability to achieve their design strength in the existing substrate. Such fasteners must consist of materials resistant to corrosion—galvanic and otherwise. Thermal Movements Since rainscreen assemblies are positioned outside the thermal envelope, they are subject to cyclic expansion and contraction due to changes in both ambient and surface temperatures. Provisions for thermal movements commonly include: • Combinations of “fixed” and “sliding” anchorage points—both for the panels and support grillage • Use of oversized or slotted holes on face-secured systems • Panel length limits • Grillage rail length limits • Prohibition of panels spanning discontinuous grillage elements There appears to be very little information available from the various rainscreen manufacturers regarding the service temperatures upon which their presumably empirical accommodations for cyclic expansion and contraction are based. By way of comparison, the glazed aluminum curtain wall industry generally recognizes design temperature changes of 120ºF (ambient) and 180ºF (material surfaces). Similar parameters should be stipulated when specifying rainscreen assemblies. FIRE Foam Plastic Insulation Section 2603.5 of the IBC defines the requirements for exterior walls of any height containing foam plastics in all but Type V construction. One such test requirement is compliance with NFPA 285. This is a flammability test demonstrating the extent to which flames will travel within a mock wall assembly (including those fitted with rainscreens) in the presence of foam plastic insulation. This testing requirement can be circumvented by the use of noncombustible mineral fiber insulation. While a decided advantage with respect to fire resistance, mineral wool offers less insulating capacity per inch than foam plastics, particularly when wet. Alternatively, many foam plastic insulation manufacturers have arranged for NFPA 285 testing of their products in common wall assemblies and offer their passing test configurations as a basis of design. These walls often include cement- and/ or clay-based claddings. Particular attention is given to the detailing of floor line firestopping, as well as window and door perimeters, to discourage the spread of fire within the wall. Combustible Cladding Section 1400 of the IBC requires that exterior walls in all but Type V construction featuring combustible claddings installed greater than 40 ft. above grade, also be tested in compliance with NFPA 285. These requirements are in addition to fire resistance rating and separation requirements for exterior walls described in the IBC Chapter 6, Table 602. Such claddings sometimes considered for use in rainscreen assemblies include, but are not limited to, wood, metal composite materials (MCMs), fiber-reinforced plastics (FRPs), and highpressure laminates (HPLs). Combustible WRBs (IBC 2012) In states using the 2012 IBC, a new provision requires that exterior walls, in all but Type V construction featuring combustible WRBs installed greater than 40 ft. above grade, also be tested in compliance with NFPA 285. Exceptions to this provision are anticipated in the 2015 IBC. ENERGY Air Barrier The 2012 International Energy Conservation Code (IECC) and ASHRAE 90.1- 2010 require that heated buildings in climate zones 4-8 feature a continuous air barrier. Compliance is defined in one of three ways: • Material/component permeability (0.004 cfm/ft2 @ 1.57 psf) • Assembly air leakage (0.04 cfm/ft2 @ 1.57 psf) • Overall building air leakage (0.4 cfm/ft2 @ 1.57 psf) The former two involve laboratory testing, while the latter involves field testing and/or commissioning. Insulation (ci vs. U) The 2012 IECC lists minimum prescriptive insulation and fenestration criteria for commercial buildings with glazing covering less than 40% of the above-grade wall area but may vary depending upon locally adopted building codes. ASHRAE 90.1 must be referenced for glazing exceeding 40% of the above-grade wall area. With respect to wall insulation, compliance can be demonstrated in one of three ways: • Use of continuous insulation (ci) meeting prescriptive R-value requirements and featuring no discontinuities other than fastener penetrations • Use of assembly U-value tables, such as those found in Appendix “A” of ASHRAE 90.1, to identify wall assemblies meeting prescriptive U-value requirements • Use of U-value calculations consistent with the practices of the ASHRAE Fundamentals Handbook. These often involve the use of commercially available analytical software It is important to note that the prescriptive ci approach often proves impractical in the presence of structural components supporting a projected wall cladding. It is further complicated when considering use of foam plastic insulation, which requires interruptions to the insulation to conform with tested NFPA 285 assemblies. These factors have increased reliance on the latter two approaches, which enable compliance based on the U-value of the overall assembly, despite limited interruptions to the insulation material. WINDOW S & DOO RS Fenestration Performance Minimum energy performance requirements for fenestration are defined in the IECC in terms of U-value and solar heat gain coefficient (SHGC). Limitations to air leakage are also included. These must be considered along with wind loading and deflection requirements of the IBC when incorporating replacements into a retrofit project. Position Retrofitting a façade with a rainscreen will usually necessitate an evaluation of the position of windows within the assembly (Figure 4). Aligned with the existing wall structure, it might be preferable to move the windows outward to fall within the insulation plane. This requires the introduction of extension brackets at the window perim- 1 9 4 • Ga rr y 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 eters. Some work will be required to restore the interior finishes at the former window plane. Hardware If replaced, the door and window hardware should be exterior-grade, resist corrosion, and meet the security requirements of the building owner and the access requirements of the building code. It should also be consistent with the overall aesthetic of the façade design. MEP FIXTURES Extensions The face of a prospective rainscreen system often stands several inches outboard of the original building face. Extensions or longer replacements must therefore be provided for all mechanical, electrical, and plumbing fixtures penetrating or attached to the building perimeter. These often include lights, louvers, hose bibs, meters, and security devices. Lighting Façade retrofit projects introduce an opportunity to improve both security lighting and accent lighting. Certain building entries must be illuminated by code. Consideration should be given to nighttime user interface and the introduction of an energy-efficient lighting scheme that complements the building without being intrusive. WATER MANAGEMENT Drainage Plane It is common for the WRB to serve as both the drainage plane and air barrier on retrofit projects. They vary between sheet goods, liquid-applied products, sprayapplied products, and combinations thereof. Many product manufacturers differ regarding the effect of driving fasteners through such barriers, particularly with respect to water entry. This is particularly controversial when comparing the effect of smoothshanked fasteners with that of threaded fasteners. Until more data are available on the topic throughout the industry, many designers continue to rely on the written position of the given WRB manufacturer. Alternatively, the proposed wall assembly, including fasteners and WRB, can be tested per AAMA 508- 07 or AAMA 508-09. Flashings Given the previously described extension of MEP fixtures and window brackets, the flashings must be carefully detailed to flange onto these projections. They are otherwise vulnerable to water that penetrates the outer rainscreen and runs along the WRB. HAZARDOU S MATERIALS Sealants Many sealants found in existing wall, window, and door assemblies contain asbestos and/or polychlorinated biphenyls. A careful survey must therefore be made to verify whether sealants will need to be abated and disposed of as hazardous materials. When sealants containing polychlorinated biphenyls are in contact with masonry, the masonry should also be tested to quantify the extent to which it is contaminated. Paint Many paints found in existing wall, window, and door assemblies contain lead. A survey must therefore be made to verify whether paint removal will require special measures. It is not uncommon for soils beneath windows to also be contaminated by paint scrapings from multiple repainting campaigns, so these too should be tested. CASE ST UDY LoGrasso Hall is a one-story building located at the State University of New York at Fredonia. Built in 1967, it houses a counseling center, health center, and international education center (Figures 6 and 7). 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 G a rr y • 1 9 5 Figure 4 – Window position. Figure 5 – LoGrasso Hall prior to exterior rehabilitation. Figure 6 – LoGrasso Hall following exterior rehabilitation. Original Construction Destructive investigations were conducted to verify the condition and construction of the cavity wall, horizontal joint reinforcement, and window/door installations. Review of the design drawings revealed that the perimeter walls were load-bearing,and that horizontal joint reinforcement was intended to bind the 4-in. brick veneer to the 6-in. concrete masonry block (separated by 1-in. polystyrene insulation and 1-in. drainage cavity) into a composite structural section. The intended composite action was particularly critical for wind loading. However, the existing horizontal joint reinforcing had corroded and was no longer tying the brick veneer to the concrete masonry backup wall. Through both visual structural reviews and mathematical engineering analysis, it was determined that the concrete masonry backup wall was still in good condition and could remain in place if reinforced. Conversely, the brick veneer (Figure 7) was deemed unsalvageable and slated for removal. PCBs were identified in the perimeter sealants of the existing windows and upper concrete banding. These were found to have migrated into the adjacent brick. Further testing revealed that PCB levels within the brick tapered off within approximately 8 in. of the window perimeters. The brick within that region therefore required disposal as a hazardous material. 1 9 6 • Ga rr y 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 Figure 7 – Existing brick veneer. Figure 10 – Terra cotta rain screen design. Figure 12 – Terra cotta rainscreen section detail. Figure 8 – Original composite wall construction. Figure 9 – Rain screen on reinforced wall construction. Figure 11 – Terra cotta rainscreen plan detail. While multiple approaches to replacing the exterior brick veneer were considered, the use of a rainscreen assembly offered the most comprehensive rehabilitation (Figures 8 and 9). In addition to addressing aesthetic considerations, many aspects of building performance such as the wall structure, drainage plane, insulation plane, and air barrier could be improved. Exterior Façade System Options In the process of isolating the scope of work for replacement of the brick veneer, various options were explored. • Option 1: Glass curtain wall • Option 2: Fiber cement board rainscreen • Option 3: Insulated metal wall panel • Option 4: Terra cotta rainscreen Option 4 was ultimately selected. A primary consideration was the perception that, as clay-based products, contemporary terra cotta panels would modernize the appearance of LoGrasso Hall while simultaneously complementing the brick of the surrounding campus buildings (Figure 10). Moderation of color and texture were introduced at the upper extremities of the walls in response to precast banding found on many of the surrounding brick buildings. By introducing parapets between the short, existing penthouses, the visual proportions of the wall elevations were improved. Scope of Work Construction began in the spring of 2012 and concluded in the spring of 2013. The building remained occupied throughout construction. The scope involved removal of the existing windows, doors, storefront, and brick veneer exterior walls. A new 6-in. concrete masonry wall was constructed to supplement the existing concrete masonry wall in carrying the roof loads, cladding loads, and wind loads. This new wythe is compositely bonded to the existing wythe with stainlesssteel ties. New windows, doors, storefront, and terra cotta rainscreen assemblies (Figures 11 and 12) were installed, complying with the 2010 building and energy codes in New York State, which are based on the 2006 and 2009 versions, respectively, of the IBC. In addition to the exterior rainscreen system, the wall construction features 2½ in. of extruded polystyrene insulation to make the building more energy-efficient. A self-adhered, asphaltic membrane serves as an air barrier, vapor barrier, and drainage plane along the outside face of the new concrete masonry. As a continuation of the thermal envelope, new insulation was extended 24 in. below grade in the form of a hard-coat EIFS system, thereby insulating the upper regions of the foundation. This also serves to insulate the heating supply ducts that are buried in the foundation walls and discharge beneath the windows. Canopies were introduced over all the building entrances. The canopies were added to the scope to combat the snow accumulation that the campus has been experiencing around the exterior doors. Wall-mounted feature lighting and recessed canopy lighting were included in the project. To better define the entrance at night, the lettering over the entry canopy is backlit with LED luminaries. (See Figures 14 and 15.) 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 G a rr y • 1 9 7 Figure 13 – External insulation detail. Figure 14 – LoGrasso Hall prior to exterior rehabilitation. Figure 15 – LoGrasso Hall following exterior rehabilitation. Code Compliance The new wall assemblies were designed in accordance with the 2010 Energy Conservation Code of New York State. This code calls for an R-value of 11.4 in Climate Zone 5, which includes Chautauqua County and the WUNY Fredonia campus, based on the percentage of window area in abovegrade walls. Design for this project is based on a continuous insulation R-value of 12.5, which corresponds with a 0.08 U-value. The Lawrence Berkeley National Laboratory software “Therm” was used to model compliance of the assembly U-value. (See Figures 16 and 17.) The use of Owens Corning extruded polystyrene insulation necessitated compliance with NFPA 285. Compliance was demonstrated through test data published by Owens Corning, wherein their product was tested in conjunction with comparable terra cotta panels. The window extension brackets complied with the “continuous steel” window head details prescribed by the test results. SUMMARY Numerous considerations must be made in the design of contemporary exterior wall systems. When retrofitting an existing wall to perform to contemporary standards, similar considerations must be extended to the proposed assembly. While not suitable for all applications, rainscreen technologies offer the possibility of improving the performance of existing walls while simultaneously modernizing the appearance of their retrofitted façades. Those specifying such systems must be acquainted not only with the codes affecting the assembly, but the varying standards and tolerances, both European and North American, associated with the proposed materials. Consensus-based standards and tolerances, adopted among manufacturers competing in North America, would help to streamline the specification process. 1 9 8 • Ga rr y 2 9 t h RC I I n t e r n a t i o n a l C o n v e n t i o n a n d T r a d e S h ow • Ma rc h 2 0 – 2 5 , 2 0 1 4 Figure 16 – Temperature modeling. Figure 17 – Thermal flux modeling.
