b'GCCC, provided that the structural support PASSIVE HOUSE METRICS for the steel plinth aligned with that of the existing structure below.Heating demand 14 kWh/ma The restricted access for space around the parkades in the Gastown area created two Cooling and dehumidification demand 6 kWh/ma challenges for construction. Firstly, the three-metre-wide alley between the parkades Primary energy demand 64 kWh/ma was the only available area for crane place-ment, so a narrow style of crane was used to move construction materials up to the Air leakage 0.6 ACH 50(design) site. Secondly, the construction materials for the project, including steel, flooring, walls The project plans include the construction of two adjoining 5,000-sq.-ft. buildings on the rooftop of the two parkades. The parkades were built side-by-side and are separated by an alleyway on the ground level. Acton Ostry Architects (AOA) is responsible for the design of the project, which was developed with input from the Gastown neighbourhood and considers the historic design aspects of the area.A CHALLENGING LOCATIONThe Gastown location and constructing the day care centres on the rooftops of the existing parkades created a number of chal-lenges for both design and construction, says Matt Wood, AOA lead for the GCCC project. Probably the most significant chal-lenge was simply the location in Gastown, where space for staging and construction work is extremely limited. The companies involved in the project had to think outside of the box to design and construct the buildings on top of a structure that was not originally designed for such use.The first step in the project involved a structural study to confirm that the existing buildings could properly support the new buildings to be added. This stage was essen-tial in that any modifications to the existing structures would have to meet current City seismic requirements and could seriously escalate the cost of the project. The existing slope on the roof of each parkade presented a design challenge in that a level surface was needed for place-ment of both buildings and outside play spaces. The sloped parkade roofs required the use of a steel plinth to provide a level surface, and the sloped roof structure below the plinth could then be used for drainage. Fortunately, the structural study confirmed the existing structure could support the FALL/WINTER 2020 11'