< PreviousPushing the Envelope Canada 13 Looking back at 2019, I can see we’ve ac- complished a lot. We had many great seminars this year: Net Zero Build- ing, Mass and Tall Timber, and the update on Pro-Demnity’s Warranty Claims, to name just a few. We toured the UL Curtain Wall Testing Fa- cility and had a rousing group discussion with the always entertaining Joe Lstiburek following his presentation, Don’t do Stupid Things. I learned a lot, and I think our members did, too. We held our seminars both in and outside of downtown Toronto, and we held another in Barrie to reach members north of the city. Our webinars also help us reach building scientists across Canada. I feel we’ve also done a better job con- necting with students preparing to enter the field of building science—young contractors, consultants, material suppliers, and research- ers. I’ve met and interacted with more students at events this year than in any year past and, as I write this, we’re preparing to award scholar- ships to a few deserving young students for the third time. As 2019 winds down, so does my term as president of the Ontario Building Envelope Council (OBEC). I want to thank the board members with whom we’ve been able to accom- plish so much. These are volunteer positions, and these people have all given a great deal of their time to keep OBEC running smoothly. I also want to welcome Ehab Naim Ibrahim as our new president. Though I’ll be staying on as past-president, I—and the rest of the board—have full confi- dence in Ehab to keep the ship on course. I also want to thank those serving on our various com- mittees: education, events, membership, tech- nical discussion groups, codes and standards, communications, and awards and scholarships. Without their help, the board would be grid- locked trying to get anything done. If you would like to volunteer to join our team, please reach out to us at info@obec.on.ca. We look forward to 2020, with a vision of con- tinuing to expand our reach and providing even more learning opportunities for our members. Keep an eye out for our e-mail invitations to next year’s exciting line-up of dinner seminars. In this issue of Pushing the Envelope Canada, we have a great line-up of informative articles for readers to peruse. On page 15, Jelena Bojanic takes an in-depth look at installing two new ethyl- ene tetrafluoroethylene (ETFE) skylights above the Panda Passage exhibit at the Calgary Zoo. A highly transparent material over a wide spec- trum of natural light, the ETFE skylights provide better conditions for the pandas. Daniel Martis discusses how to analyze confused spaces (e.g., crawl spaces, attics, and parking garages) and determine where they be- long in relation to the air, thermal, and vapour barriers. In his article on page 20, he also takes a look at retrofitting approaches when ventilation becomes part of the equation, in order to ensure condensation and mould problems are avoided. On page 23, Anna Farbis and Dr. Kim Pressnail update readers on the architectural, building envelope, and mechanical design of the Gemini New-Build; a low-rise residential home designed from the results and successes of the Nested Thermal Envelope Design concept. Matt Carlsson explores a proposed retro- fit strategy for high-rise residential buildings involving compartmentalization of apartment units and decentralized in-suite ventilation with heat recovery to determine the impact on over- all space heating energy for the building and the associated greenhouse gas emissions (page 26). Flip to page 31, where Kevin Zhang and Dr. Russell Richman discuss the importance of understanding and embracing hygrothermal modelling to study the variability of sorption isotherms in oriented strand board and plywood sheathing. In his article on page 34, Rick Buist walks readers through the typical causes of green roof failures, discusses where and why things go wrong, and offers remedies to improve quality of vegetated roofing system designs. Kent Schultz and Jesse Moore tackle the topic of whole building airtightness tests not ac- commodating phased occupancy and skewing results for high-rise buildings. On page 37, they highlight a guarded airtightness test recently con- ducted on a high-rise building to ensure results focused on only the area desired, assessing the guarded method and discussing logistical con- siderations, high-level results, and future applica- tions of the test. This issue’s Architect’s Approach article tells a tale of two iconic bridges, the Victoria and the Champlain, in Montreal, Quebec. On page 40, Paul Sheehy compares the cost of quality engineering versus value engineering. He also delves into the different processes, practices, philosophies, and outcomes with each project. I want to thank our board members and committee members, the authors of all articles in this publication, and the speakers at our din- ner meetings. I also want to thank all of OBEC’s membership. Without your participation, OBEC wouldn’t exist. Let’s continue to reach out and expand this organization. Together, through sharing our collective knowledge, we can make a better, safer, and more durably built environ- ment for everyone! n n n n UP FRONT Message from the President OBEC President Ian Miller, P.Eng., LEED AP, CCCA Project Principal, Regional Manager (S.W. Ontario) Pretium Engineering Inc. OBEC 2019 BOARD OF DIRECTORS President Ian Miller, P.Eng., LEED AP, CCCA Pretium Engineering Inc. Vice-President Ehab Naim Ibrahim, OAA Int., MRAIC, LEED AP Gamma North America Past-President & Chair, Membership Committee Marco Guzzo, Dipl. Tech. Engineering Link Inc. Secretary / Treasurer Alen Vrabec, P. Eng., BSS, PMP BGIS Chair, Building Science Specialist Committee Continuing Education Mila Aleksic, B.Arch.Sc., M.A.Sc. George Brown College Chair, Codes & Standards Committee Michael Rekker, C.E.T., BSS Tacoma Engineers Inc. Chair, Communications Committee Meagan Kikuta Tremco Roofing Chair, Events Committee Robert Quattrociocchi EllisDon Chair, Scholarships & Awards Committee Gauss Wong, B.Eng., P.Eng. Sense Engineering Chair, Technical Committee Mark Clyde, Dipl. Arch., BSS, PMP Henry Company OBEC STAFF Event Coordinator Beth McKenzie Membership Coordinator Liz Burns Operations Manager Sherry DeneshaPushing the Envelope Canada 15 The former Eurasian Gateway & Elephant Crossing at the Calgary Zoo has been re-used and re-adapt- ed multiple times since 1963 to house ani- mals, including elephants, giraffes, and the more recent rhinos and Komodo dragons. In 2015, the Calgary Zoo announced the Giant Pandas would be transferred from Toronto in 2018 and would be housed in the former Eurasian Gateway building at the Calgary Zoo. The well-being of the pandas was predi- cated on creating a habitat in which the animals would thrive. The Calgary Zoo, along with the support of the project de- sign team, decided to install two new ethyl- ene tetrafluoroethylene (ETFE) skylights above the panda exhibit. ETFE is a highly transparent material over a wide spectrum of natural light, which would provide better conditions for the pandas. Read Jones Christoffersen (RJC) provided technical support for design considerations, including snow and wind design loads, hail impact, temperature fluctuations, and recommendations to address inherent air barrier deficien- cies and thermal bridging. Support was also provided during the installation to ensure the intended design parameters were achieved and that performance aligned with current industry standards. The ETFE skylights were designed and manufactured in Germany and installed by a local contractor. These are some of the first ETFE installations in western Canada. BACKGROUND The ETFE skylights were proposed for this project because the material is one of the few tensile fabrics used for roofs that allow UV light to pass through and com- plies with the living building challenge “Red List” material restrictions. Other important considerations for choosing this product included cost, future recyclability, embodied energy, durability, chemical re- sistance, etc. RJC’s Calgary office, along with a few other offices (Edmonton, To- ronto, and Vancouver) worked together to research a product that incorporated key design objectives and was within the client’s budget. Originally invented for the aeronaut- ics industry, ETFE was introduced to the construction industry in the 1980s and has since been used on projects around the world. It is a lightweight material, weighing approximately one per cent of the weight of glass, and allows up to 95 per cent of light transmission. The latter can be adjusted by varying the number of cushions and applying films. Thermal performance is higher in a three-layer ETFE system versus a single-layer system. To incorporate the new dome-shaped ETFE skylights above the panda exhibit, the existing glulam beam-supported metal roof deck underwent structural and build- ing envelope modifications. DESIGN CONSIDERATIONS There were several design considera- tions the team had to take into account while working on this project, from cushion design and the supporting structure to the air barrier and drainage, and to thermal performance. Performance Pandemonium: Designing & Modifying the ETFE Skylight System for the Calgary Zoo’s Panda Passage Exhibit By Jelena Bojanic, B.Sc., EIT, Project Engineer, Read Jones Christoffersen Ltd. Figure 1. A manufacturer’s drawing showing the thickness of the layers in the ETFE skylight.1 Da Mao, an adult male giant panda, in Panda Passage. Photo credit: Calgary Zoo, www.calgaryzoo.com. Two new ethylene tetrafluoroethylene (ETFE) skylights above the panda exhibit. ETFE is a highly transparent material over a wide spectrum of natural light, which provides better conditions for the pandas. n n n FEATURE16 Fall 2019 • Ontario Building Envelope Council FEATURE n n n CUSHION DESIGN AND SUPPORTING STRUCTURE For the ETFE skylight to resist specified snow and wind loads and hail impact, the design was focused on the individual foil thickness, number of layers, and internal cushion pressure. The cushions are inflated with a built-in blower / compressor that main- tains air between the individual layers and pre-stresses each layer, resulting in a dome- shaped skylight that is stable against wind and snow loads.1 The skylight manufacturer used RJC’s recommendations for snow and wind loads and Calgary’s temperature fluc- tuations to ensure conformity with the local standards. RJC posed the question regarding hail impact damage testing for the ETFE. The manufacturer provided a paper outlining test results from experiments conducted in Zurich and Switzerland. It also highlighted case studies with hail damage. The results showed that ETFE can, indeed, be damaged by hail, depending on the size of individual hail pieces and the temperature of the film itself.2 The extent of damage varies from dimpling of the surface to full puncturing.2 Da Mao is right at home in Panda Passage. Photo credit: Calgary Zoo, www.calgaryzoo.com. Given that Calgary, Alberta experiences se- vere hailstorms during spring and summer months, with hail pieces ranging from 25 to 50 millimetres in size, this was an impera- tive design load to consider. The solution was incorporating a three-layer system with a slightly under-inflated outer cushion. The inner and outer layers (IL and OL) are each 250 micrometres thick, while the middle lay- er (ML) is 100 micrometres thick, as shown in Figure 1 (on page 15). The two cushions are inflated to different internal pressures, with the inner cushion at 300Pa, and the outer at 250Pa.1 The translu- cency of the ETFE foil was reduced slightly, with a three-layered system; however, the re- sultant light transmittance was approximate- ly 76 per cent,3 which was within an accept- able range for the panda exhibit. The inner ETFE layer is supported by steel pipe arches fastened to steel perimeter beams made of square tube sections. The beams are further supported by steel columns, which are also made of square sections. Tension rods are incorporated throughout the frames to miti- gate deflection of the structure. AIR BARRIER AND DRAINAGE The air barrier plane for the ETFE sys- tem relies on multiple components, including the ETFE foil, the ethylene propylene diene monomer (EPDM) edge gasket, the EPDM cover gasket, and the air barrier membrane tied from the aluminum profile to the ex- isting roof deck. The manufacturer’s shop drawings had inherent air barrier and drain- age flaws. The design showed a condensa- tion gutter that drained externally through the air barrier membrane (see Figure 2, part 23, on page 17) via four drainpipes, two on each of the east and west elevations and none on the south and north elevations. The drainpipes were positioned at quarter-points with a large spacing. A metal sheet section was shown to extend from the underside of Pushing the Envelope Canada 17 n n n FEATURE Figure 2. A manufacturer’s drawing showing the external drainage (red lines) through the air barrier (blue line).1 Figure 3. A manufacturer’s drawing showing the revised ETFE system with internal drainage (green lines) and the air barrier detail (blue line).1 the aluminum profile to the exterior sill (see Figure 2, part 41), creating thermal bridging within the assembly. Calgary experiences significant temperature fluctuations and ex- treme cold weather conditions, with a winter design temperature of -32˚C.4 Openings to the exterior would introduce cold air into the system, resulting in higher levels of conden- sation and freezing of any moisture in the system. Ice build-up inside the system could block the intended drainage path and dam- age connections along the gutter. Typical metal skylights glazed with sealed units incorporate pressure equalization and internal drainage without impacting the air barrier or resulting in thermal bridging. RJC suggested these items be revised, as they were not acceptable per industry standards. The proposed spacing between drainpipes was likely inadequate for water to access and expel out of the system and should be revised. The sill should be water- and air- tight, with no unsealed openings through the air barrier. RJC suggested providing internal drainage if draining to the exterior was not a possibility without affecting the air barrier. The metal sheet (see Figure 2, part 41) was to be modified to eliminate the thermal bridge through the skylight sill. The manufacturer revised its design fol- lowing most of RJC’s recommendations. Internal drainage was provided through the condensation gutter and directed to the in- terior panda space. The layout of the drain- pipes was not changed during design re- visions. Thermal bridging was mitigated by removing the metal sheet section intended to provide support for the roof membrane tie-in. The final design included tying the air barrier into the aluminum profile, creating a continuous air barrier plane. Figure 3 (on this page) shows the revised section of the system. THERMAL PERFORMANCE The thermal transmittance (U-Value) for the ETFE aluminum profile was calculated to be 5.90 W/m2K, 1.9 W/m2K for the three layered ETFE cushion and 2.1 W/m2K for the combined system.3 These values were cal- culated by the manufacturer using set tem- perature parameters of 20˚C for the interior and -10˚C for the exterior.3 Condensation is expected along the EPDM edge gasket and along the aluminum base. Realistically, a PART NO.PART NAME 1Aluminum cover profile 2EPDM edge gasket 4Aluminum frame profile 5Condensation gutter 7EPDM cover gasket 9, 10, 11, 12Stainless steel hex head bolt, washer, nut 22Metal sill flashing 23Condensation drainpipe 24, 25, 26Outer, middle, and inner layer of ETFE foil 29Air barrier 41Metal sheet higher volume of condensation is expected, as Calgary temperatures can reach -32˚C4 during winter. This moisture is intended to drain via a condensation gutter underneath the aluminum profile, and to expel from the system via drainpipes. To address air- and water-tightness con- cerns ahead of time, RJC asked for a small corner sample of the aluminum profile that would show the corner joinery and frame sealing. Unfortunately, the corner sample was not provided; rather a small, typical sec- tion of the frame arrived and did not show either items. RJC was told that the EPDM cover gasket would be glued at the corners with an EPDM adhesive and that the alum- inum frame would not be sealed at the cor- ners. Water that gets through the frame would be captured within the condensation gutter and drained to the interior. CONSTRUCTION In the construction industry, it is often ex- pected that as-built details won’t always align with the initial design. This is tolerated to a degree, because one cannot predict the exact site conditions during construction. Identify- ing and correcting these deficiencies during early construction stages is crucial for a pro- ject to be on schedule and to avoid additional costs. During installation, deficiencies with the skylight frame and ETFE cushions were noted. One of the first obvious issues was the inadequate gap at the mitered corners. The aluminum profiles were misaligned so the coupling surfaces at the corners were off- set from one another. The misalignment was partially due to the aluminum profile not being set true and level. The structural steel below the aluminum profile was not Table 1. Parts reference Figures 2 and 3 on this page.18 Fall 2019 • Ontario Building Envelope Council perfectly level, and the aluminum profile did not incorporate adjustability (e.g., levelling nuts or incremental shims). The suggested improvement was for the contractor to ad- just the positioning of the aluminum frame by using adjustable leveling bolts / nuts (see parts 9, 10, and 12 in Figures 2 and 3). During a subsequent review, standing water was visible in the skylight gutter after a rainfall. This was prior to the ETFE foil being installed. As suspected, water was not drain- ing properly; the system did not incorporate a transitional slope from the north and south elevations (without drain openings), nor to the east and west elevations (with drain openings). The drain layout was not practical for the perimeter of the skylights. Water was actively dripping through the condensation gutter corners and at the bolted connections, indicating that the membrane liner was not continuously sealed in these locations. The repair strategy included installing additional drain openings on the north and south ele- vations and additional sealing of the corners and the bolted connections. Once the ETFE cushions were attached to the aluminum profile, they were inflated with the blower. Each skylight was inflated in approximately one hour, with minor adjust- ments required for the EPDM edge gaskets, which were displaced during the ETFE in- stallation. The contractor used ETFE tape for additional reinforcement at the corners. The air barrier membrane was tied in from the roof deck onto the new built-up curb and tied into the aluminum profile. In addition to the air barrier membrane, the contractor tied the thermoplastic polyole- fin (TPO) single-ply roofing membrane into to the aluminum profile, increasing the over- all material thickness. This created problems for installing the EPDM cover gasket and cover plate. The solution was to terminate the TPO membrane at the top of the curb, instead of extending it onto the aluminum profile to allow for sufficient and continu- ous pressure between the gasket and the air barrier. The metal sill flashing was installed with- out a slope, resulting in standing water along the sill and EPDM gasket. The flashing was modified to ensure it slopes away from the cushions and the main gasket. The EPDM cover gasket was glued at the corners and reinforced with an additional EPDM strip, using an EPDM adhesive to reduce the risk of moisture ingress. Field diagnostic testing such as air leak- age characterization and water penetration resistance could not be completed due to project schedule restraints that impeded safe access for testing. Once the building was commissioned to normal interior operating parameters, RJC recommended thermo- graphic scanning from the exterior. CONCLUSION Most of the flaws identified during the in- itial design and construction were corrected during each phase by being proactive with input and discussing concerns with the manu- facturer and contractor. As the building en- velope consultants, the goal was to ensure the design and installation of the ETFE skylights conformed to industry standards, with the aim of improving the long-term durability of the ETFE skylights and its supporting struc- ture and eliminating air and moisture barrier deficiencies. By providing recommendations for design loads, air barrier, and drainage components and consistent input during construction, this goal was achieved. The key benefit of the building envelope consult- ing services provided by RJC was the team’s local knowledge of practical issues that af- fect building envelopes in Calgary and the ability to bring these to the forefront, as- sisting the sophisticated ETFE manufactur- er from Germany. Considering this is not a typical product installed by the construction industry in west- ern Canada, several issues were anticipated during design and construction. As this sys- tem installation becomes more mainstream in the future, these issues will likely diminish as designers and installers become more fam- iliar with the product. Jelena Bojanic, B.Sc., EIT, is a building en- velope and restoration project engineer at Read Jones Christoffersen Ltd. (RJC). Since joining RJC in 2014, Jelena has gained a variety of project experience in the assessment and resto- ration of structures and building envelopes. REFERENCES 1. Seele Cover GmbH, Shop Drawings and Structural Analysis ETFE Skylights, Obing Germany, 2017-04-28 2. Peter H. Flueler, Swiss Federal Lab- oratories for Materials Testing and Research, Flueler Polymer Consult- ing GmbH, Zurich Switzerland, ETFE Membrane Structures: And What About Hail Impact Resistance?, RCI 22nd Inter- national Convention, pp. 29-37 3. Seele Cover GmbH, U-Value, G-Value and Light Transmission ETFE-Cushion, 2017-06-07 4. Alberta Building Code 2014, Volume 2 The steel frame structure for the ETFE skylight.The ETFE skylight above Panda Passage being inflated with a blower. FEATURE n n n Next >