The William Osler Healthcare Group is completing a new hospital facility in Brampton to operate as an open public hospital and general healthcare centre. The $550 million project comprises the design, construction and commissioning of the 608-bed hospital, the first public-private partnership model project in the region. Construction work began in November 2004. The hospital opened in October 2007.
The new hospital will house 608 beds and 20 operation rooms in over 1.2 million sq ft of space that will be able to accommodate 90,000 emergency visits, 110,000 outpatient visits and 4,250 births per annum. The project aims at expanding oncology services, ambulatory services, a renal dialysis lab and cardiac catheterization. The hospital will handle 160,000 ambulatory care visits and 89,000 emergency department visits.
WORK IN PROGRESS
Construction work is near completion on this new hospital, one of the largest health infrastructure projects underway in Canada. More than 750 workers were involved in the construction.
The hospital and the community are contributing 30% of the total construction cost of the new hospital, while the Province of Ontario is providing the other 70%.
The Healthcare Infrastructure Company of Canada (THICC), a special purpose project company established by the sponsors, Carillion Canada Inc and Ellis Don Corporation, developed the project using an Alternative Financing Partnership. THICC signed the concession contract on 23 November 2004.
With the successful award of the new William Olser hospital on Brampton to The Healthcare Infrastructure Company of Canada (THICC), a special purpose project company established by the sponsors, Carillion Canada Inc and Ellis Don Corporation, THICC signed the concession contract on 23 November 2004 and the clock for completion began to tick.
The Request for Proposal (RFP) requirements for the project called for a high-performance building envelope that respected the required aesthetics of the RFP as interpreted by the builder’s architect, Adamson and Associates.
The builder, Ellis Don, was most concerned with long-term performance that required minimal maintenance of the building envelope. Fast completion of the building envelope to allow the interior trades to commence work was another important factor in the selection of the building envelope.
RFP WALL DESIGN REQUIREMENTS
•Use materials that are associated with high quality construction
•Construct the building using high quality building materials so the finished product is perceived as high quality by building users
•Use external building materials that are appropriate, attractive, enhance the building design and are well detailed
•Enrich the experience of the building surface and form design using the colour and texture of the building elements
•Provide for potential vertical expansion
•Exceed the building efficiency requirements of the general, mandatory and prescriptive provisions of the Model National Energy Code for Buildings, by 30%
•Provide 5% of the building’s total energy requirements using on site renewable energy systems
ARCHITECTURAL RULES FOR EXTERIOR WALL SYSTEMS
•Design exterior walls as cavity walls
•Construct cavity wall systems using a “precast concrete back up wall system”
•Comply with requirements of CSA Standard A23.4 – Precast Concrete - Materials and Construction
•Precast panel back up construction must form the inner wythe in the cavity wall system and incorporate insulation, air, vapour, drainage and compartment flashings
•Precast concrete back up construction shall carry all live, dead and imposed loadings of the building envelope
•Precast panels to be form finished on the cavity side and smooth trowel finish on the interior face
With the interior wall element being prescribed in the RFP, selection of the exterior veneer assembly to complete the cavity wall was reviewed. A masonry veneer on precast concrete back up construction met the RFP requirements, but considering the magnitude of the WOHC building envelope area, installation of the masonry veneer wall on site would not meet the project schedule.
A decision to use an architecturally finished precast concrete wall, complete with insulation, air cavity, and self-supporting precast backup wall was made. This rain screen wall system is based on the principle of controlling the forces that can move water through small openings rather than the elimination of the openings. This system is considered to be a cavity wall system.
Joints in a rain screen wall assembly have two lines of defense for weatherproofing. The typical joint consists of a rain barrier near the exterior face and an air seal close to the interior face of the panel. The rain barrier is designed to shed most of the water from the joint, and the wind barrier or air seal is the demarcation line between outside and inside air pressures.
Between the two caulking stages in the joint is an equalization chamber that must be vented and drained to the outside. The exterior sealant or rain barrier prevents direct entry of most airborne water. If airborne water (wind driven rain) does penetrate this barrier, it will drain off in the air chamber. It is this air chamber, which is vented at the joint to the outside environment that forms the pressure equalization space.
With pressure equalization, water must not penetrate the wall system far enough to cause any problems. The wind barrier/air seal will normally be subject to water penetration by capillary action, but since the outside air that reaches the seal has already been stripped of its water content, no moisture enters.
Water in the cavity is drained at the transverse caulking seal, at the intersections of the vertical and horizontal joints or at the head of window by flashings. This transverse seal (flashing) is sloped down towards the exterior of the panel, draining away any moisture.
This transverse seal (flashing) also acts as a baffle to prevent the vertical movement of air in the vertical joint chamber. Vertical air movement is caused by wind and outside air turbulence and thermal stack effect. Vertical and horizontal air movement is further curtailed with the introduction of baffles at the perimeter of the panel, in the 12mm air space. The bottom baffle is vented to allow pressure equalization to occur, and to drain any moisture in the 12mm panel cavity.
A continuous interior sealant is necessary to ensure a good air/vapour barrier. Since many locations on a building have inaccessible areas behind columns and slab edge beams, the preferred method of sealant installation is from the exterior. Suitable joint sizes were be used to allow the installation of the interior sealant bead.
With the selection of a complete architectural precast concrete wall assembly, a cavity wall system has an impermeable precast concrete exterior panel that performs as the facing to the cavity wall. The exterior wythe is tied back and supported by the interior structural wythe (precast concrete back up wall) using stainless steel ties and reinforcing. There are no materials in a precast cavity wall subject to water absorption, deterioration or mold growth.
The space between the two precast concrete wythes is where the insulation, air vapour retarder, air space, drainage and compartment flashings are incorporated.
The precast concrete panel back up construction was design to ensure that all gravity loads were transferred to the building’s structural columns, or adjacent to the columns on the floor slab. This eliminated expensive poured in place reinforced concrete construction at the perimeter of the floor plates to take mid-span loads. Only lateral loads are transferred into the floor plate at the mid-span locations.
The large panels minimize the joints that are caulked at the front of the exterior wythe of precast concrete and at the back of the insulation to maintain the thermal performance at the joint.
EARTHQUAKE AND WIND PROVISIONS
The RFP and 2005 NBCC require hospitals to function properly as post disaster structures designed to survive and serve the public after an earthquake or other emergency. The architectural precast concrete insulated wall panel system was designed for increased wind and seismic loading.
An earthquake may cause minimal damage at expansion joints and sealant joints between precast panels. Reduced sealant and joint performance after an earthquake should only compromise the performance of the building envelope by a small margin and cause no disruption of internal building functions. Precast panel systems performed well in the Northridge Earthquake in California in the early 1990s.
Likewise, a hurricane can put extreme water driven pressures on the building envelope. The precast concrete exterior wythe will prevent any ingress of water through the panels. The caulked joint behind the exterior precast “screen” and cavity will ensure that moisture will not migrate into the building, but be drained out at flashed joints or window heads. The jointing of precast walls to dissimilar materials also needs to perform in harmony with the precast envelope to ensure the complete building envelope.
The RFP describes how successful proposals will address thermal wall performance and will incorporate the strategies and technologies of the LEEDTM Rating System Version 2.0. Components constructed of concrete have a thermal mass effect - the ability to have enough heat-storage capacity to moderate daily indoor temperature swings by reducing peak heating and cooling loads.
ARCHITECTURAL PRECAST CONCRETE
In all, 1796 precast concrete panels were installed on the exterior of the new hospital covering an area of 23,600 sq m (254,100 sq ft). Panels contained sandwich insulation to meet project requirements except at the stairwells where insulation was applied behind the panels at the jobsite.
The panels have two different face mixes – buff and green. Several textures were employed – light and medium sandblasted, plus a light vertical ribbed finish that was used as a accent.
The result of the RFP is a customized precast concrete solution entirely suitable for achieving the industry’s new way of delivering P3 building programs. The precast solution was able to met or exceed the requirements that the Healthcare Infrastructure Company of Canada was tasked with providing.
Sponsors: William Osler Health Centre and the Ontario Ministry of Health and Long Term Care
Construction and development of the project: Ellis Don-Carillon Joint Venture
Non-clinical services: Carillon Services (WOHC) Inc. - building maintenance, patient food, housekeeping, patient transportation, laundry and linen, materials management, security, parking and retail
Equity providers: Borealis Capital, Carillion plc, Ellis Don - a consortium of banks is funding the project
Project architect: Adamson and Associates