Glazing System Remediation Project Brook Van Dalen & Associates - PowerPoint PPT Presentation

Bank of Canada Headquarters Building, Ottawa Glazing System Remediation Project Brook Van Dalen & Associates Limited

• Located downtown Ottawa on the block bounded by Wellington Street to the north, Spark Street to the south, Kent Street to the west and Bank Street to the east • The original head office building for the Bank of Canada was constructed on the site in the 1930’s

• In the 1970’s an atrium and two new towers were designed and constructed to partially enclose the original building • Arthur Erickson, the lead design architect, selected a metal and glass enclosure for the new construction, distinct and widely recognized because of his choice of copper for all the exposed exterior metal components

• Exterior appearance of towers and Atrium is consistent, but actually two different types of glazing systems • In addition to use of copper, unique features of glazing system include: – Slab to slab glazing units – Triangular profile caps

Towers – Most similar to conventional curtain wall – Primary vertical mullions ‘continuous’ with stack joints at each slab level – Mullions anchored to concrete floor slabs – Vertical plates and caps do not run through spandrel region – Very narrow module (2.5’) – Very short spandrel height – 12th floor incorporates sloped glazing system

Atrium • Most similar to conventional window wall • Panels of framing set between floor levels, but outside of structure • Horizontal rails anchored to structural steel beams • Wider module (5’) • Very short spandrel height • No sloped glazing

• Original system design incorporated insulating glass units with reflective coating, air fill • Spandrel assemblies included copper panel, 25 mm insulation, galvanized pan • Coupled with height of glass and amount of framing used, system very poor with respect to thermal performance

• All systems were intended to be drained • Plates incorporated drainage slots, caps did not • Caps on horizontal rails intended to drain into caps on vertical mullions • Drainage to exterior intended through gap at base of each vertical mullion cap, on top side of horizontal cap

So…….why are we here today to talk about remediation of the glazing system(s)???

• Prior to the remediation project, a study of the glazing system was commissioned by the Bank in response to three primary concerns: – Detracting appearance of caps on exterior wall (deformation and need for mechanical fastening) – Water leakage – Rate of IG unit failure

The results of the preliminary study caused the Bank to initiate the Exterior Glazing System Remediation Project

Key Success Factors • Resolve and improve the technical performance efficiently • Minimize disruption to the occupants • Respect the integrity of the Architecture

Design/Build for a Curtain Wall Remediation?!! • A unique contract for a unique challenge • A single obligation of result • The strength of a team from conception to completion

Remediation Project Team • BANK OF CANADA • VANBOTS CONSTRUCTION CORPORATION • FERGUSON NEUDORF GLASS INC. • BROOK VAN DALEN & ASSOCIATES LIMITED

Technical Challenges • Understand cause and develop solution for each of the three primary concerns: – Detracting appearance of caps on exterior wall (deformation and need for mechanical fastening) – Water leakage – Rate of IG unit failure • Maintain (improve) appearance of wall, including preservation of patina on any new copper

Detracting Appearance of Caps on Exterior Wall • Original system used a dress cap of copper applied over an extruded aluminum snap cap • Poor combination of materials to have in contact, in light of high potential for galvanic reaction

Galvanic Series of Metals • MAGNESIUM MAGNESIUM ALLOYS ZINC ALUMINUM 5052, 3004, 3003, 1100, 6053 CADMIUM ALUMINUM 2117, 2017, 2024 MILD STEEL (1018), WROUGHT IRON CAST IRON, LOW ALLOY HIGH STRENGTH STEEL CHROME IRON (ACTIVE) STAINLESS STEEL, 430 SERIES (ACTIVE) 302, 303, 321, 347, 410,416, STAINLESS STEEL (ACTIVE) NI - RESIST 316, 317, STAINLESS STEEL (ACTIVE) CARPENTER 20CB-3 STAINLESS (ACTIVE) ALUMINUM BRONZE (CA 687) HASTELLOY C (ACTIVE) INCONEL 625 (ACTIVE) TITANIUM (ACTIVE) LEAD - TIN SOLDERS LEAD TIN INCONEL 600 (ACTIVE) NICKEL (ACTIVE) 60 NI-15 CR (ACTIVE) 80 NI-20 CR (ACTIVE) HASTELLOY B (ACTIVE) BRASSES COPPER (CA102) MANGANESE BRONZE (CA 675), TIN BRONZE (CA903, 905) SILICONE BRONZE NICKEL SILVER COPPER - NICKEL ALLOY 90-10 COPPER - NICKEL ALLOY 80-20 430 STAINLESS STEEL NICKEL, ALUMINUM, BRONZE (CA 630, 632) MONEL 400, K500 SILVER SOLDER NICKEL (PASSIVE) 60 NI- 15 CR (PASSIVE) INCONEL 600 (PASSIVE) 80 NI- 20 CR (PASSIVE) CHROME IRON (PASSIVE) 302, 303, 304, 321, 347, STAINLESS STEEL (PASSIVE) 316, 317, STAINLESS STEEL (PASSIVE) CARPENTER 20 CB-3 STAINLESS (PASSIVE), INCOLOY 825NICKEL - MOLYBDEUM - CHROMIUM - IRON ALLOY (PASSIVE) SILVER TITANIUM (PASS.) HASTELLOY C & C276 (PASSIVE), INCONEL 625(PASS.) GRAPHITE ZIRCONIUM GOLD PLATINUM

Remedial Work Requirements • Eliminate direct copper/aluminum contact • Replace all plates and caps • Replace all glass units • Reduce water passage through outer face of system • Renew inner seals of system for air and water tightness • Provide clear drainage for glazing and spandrel cavities

Remediation Procedures 1. Strip and discard all copper dress caps 2. Strip and discard all aluminum pressure plates 3. Strip and STORE all copper spandrel panels, discard mirror column cover panels 4. Strip and discard all spandrel insulation and backpans 5. Verify condition of anchors and take necessary remedial action

Remediation Procedures (cont’d) 6. Reseal expansion joints in vertical mullions 7. Install new galvanized spandrel backpans,properly sealed to framing 8. Install new corner blocks at framing intersections, renew joinery seals 9. Remove and discard all IG units 10.Install new IG units

New Glass Units • New glass product selected to match, as closely as possible, reflectivity of original glass • Also incorporated: – low-’E’ coating – argon gas fill – heat strengthening for typical units – laminated glass at lowest levels and at 12 th floor sloped section

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Glazing Challenges • Essential to maintain minimum dimension for drainage cavity around new units while maintaining adequate bite • Many of Atrium framing openings out of square • All glass ordered for ‘typical’ opening size, which often did not accept glass with appropriate clearance • Checklist of remedial work to address non-standard openings included: – Temporarily releasing panel anchors, jacking framing and refastening anchors – Cutting off framing nosing and applying new nosing extrusion ‘off-centre’ on framing – Installing new interior stops and structurally glazing one or more edges of new IG units

Remediation Procedures (cont’d) 11.Install new spandrel insulation and STORED copper spandrel panels 12.Install new pressure plates

Elimination of Direct Copper/Aluminum Contact • Eight new pressure plate profiles designed to match width of original plates, profile of original caps • Plates designed to receive new copper caps • Selected pultruded fiberglass as new plate material • Iterations required to optimize design

Thermal Impact of New Plates

Remediation Procedures (cont’d) 13. Install new copper caps

New Copper Caps • Eight 8 new caps designed to pair with new plates • Step #1 – create break form samples based on initial production samples of plate • Step #2 – iterate combinations of gauge, temper and profile with break form to obtain balance of fit, impact resistance and ‘workability’ • Step #3 – produce roll form to mimic selected break form sample • Step #4 – check fit of initial roll form product ON SITE • Step #5 – produce required lengths of cap with mitres, weep slots, etc. • Step #6 – apply patina to finished caps