Mountain Equipment Co-op Store

Salvaged materials and energy efficiency paramount for "green" infill retail building.

Wood Le Bois, Spring 2001 – Linda Chapman

Program
The design process of the C2000 standards is based on the early integration of all mechanical. electrical, and structural building systems with the architectural and site design to produce a more cost effective, energy efficient and environmentally benign building. This means forming a co-operative design team of consultants that meets early on as a group, preferably with the help of a green building advisor, to map out the best solutions for design and construction.

Energy modelling was used throughout the design process and wis crucial to the achievement of a 56% improvement in energy consumption over the Canadian Model National Energy Code for Buildings - an estimated annual energy savings of $22,000.

Energy modelling favoured a two storey building option. A two-storey building was, moreover, felt to provide better retail space with more wail display area, potential for a two-storey atrium and more height for the interior climbing wall.

The new building incorporates many ideas, which further MEC's green building mandate, including a roof rainwater cistern, extensive daylighting, a high volume of recycled materials and design for future disassembly.

We disassembled the existing building and salvaged over 86% of its materials for reuse in the new building or to be recycled offsite. In fact, over 56% of the materials used, by weight, in the new building are composed of recycled content or salvaged items.

The construction manager did an exemplary job of finding used materials, but was always working within time, distance and cost constraints. For example, we specified used-plywood sheathing for the exterior, but none was available at the time. As used materials become better understood and more common, an infrastructure should develop fur easier sourcing.

Structure
The original building was carefully disassembled so that we could re-use or recycle as many elements as possible. The original steel columns, beams and open web steel joists had been sized for Ottawa snow loads but not for a retail door load.

We decided to re-assemble the steel structure, including both salvaged and new components, on the second floor of the new building to support the new roof. Following the existing structural grid dimensions for the new portions of the building made the re-assembly fairly straightforward.

The original terrazzo floor and most of the foundations were retained, and we rebuilt the two-hour fire-rated party wall on the east side of the building to comply with current fire and earthquake construction standards.

Much discussion centered on the new structural system for the ground floor. Certainly steel or concrete would be simple and cost effective, but were not given very high environmental ratings. We knew that large salvaged Douglas fir timbers from old log booms on the St. Lawrence and Ottawa rivers were available. We decided to choose them for their aesthetics, low embodied energy and recycled or salvaged "content."

The engineers were asked to make the timber frame as light as possible. Beams of 292 x 292mm [12x12] span between columns on a 6.8m [22ft.] grid. The engineers beefed up the lower face of the beam at mid-span by lag bolting on a 51 x 241mm [3x10]. This is engaged at each end by a 140 x 241mm [6x10] knee brace that transfers compression loads to the column. So as not to reduce the section size of the column, the knee brace was not notched into the column but rather was lag bolted to the face of it while also resting on blocking bolted to the side of the column.

Wall Selection
The design team used the Green Building Assessment Tool, a chart that compares the attributes of wall types according to the categories of re-useability, recycled content, embodied energy, longevity, structural efficiency, cost, thermal value, and ease of construction. Based on this evaluation, we chose a 235mm [12x10] wood I joist system with its R-value of 35 [RSI 6].

With a post and beam structure, the walls are non-loadbearing and extend the full two storeys in a balloon frame fashion. Bolted steel brackets at the door line secure the I-joist studs to the timber floor beams. The stud walls are insulated and sheathed with oriented strandboard and self-adhesive elastomeric air barrier strips taped at the joints. The various claddings, chosen for visual interest, were applied as a rainscreen with a 19mm [3/4-inJ backup air space.

Code Brief
The National Building Code of Canada [NBCC] classifies the building as a Mercantile Occupancy. According to clause 3.2.2.62, sprinklered Group E buildings up to two storeys may have a building area of 1,800 sq.m [19,370sf] if floor assemblies and load-bearing elements have minimum fire-resistance ratings of 45 minutes. This rating is easily provided by the heavy timber construction.

Client: Mountain Equipment Co-op Ottawa Construction Manager: Justice Construction Architect: Linda Chapman Architect & Christopher Simmonds Architect in Joint Venture Energy Modelling: Leslie Jones & Associates Inc. Structural Engineer: Cleland Jardine Engineering Limited C2000 Facilitator: Enermodel Engineering Landscape Architect: Jim, Lennox Photos: Ewald Richter

Product Specs

  • Wood Products
    • salvaged Douglas fir 292 x 292mm columns and beams, 140 x 292mm joists, 140 x 241mm knee braces, imd structural deck from Goodfellow Inc.
    • recycled elm plank floor and baseboards
    • 241mm wood I joists by Alljoist
    • 12.5mm OSB sheathing
  • Thermal and Moisture Protection
    • Insta-seal foam sealant, eco-blend by Flexible Products
    • 2 ply modified bituminous sheet membrane by Monsey-Bakor Inc.
    • Tyvek moisture barrier
    • Monsey-Bakor Blueskin SA air barrier sheet membrane
    • FXL40 semi-rigid mineral wool insulation batts, by Roxul Inc.
    • Rigid mineral wool roof insulation boards by Fibrex Insulations Inc.
    • 100% post consumer cellulose insulation by Thermo-Cell Industries Ltd.
    • Cemplank fibre-cement siding, by F.C.R Inc., from Goodfellow
  • Wood Windows
    • double glazed wood windows with aluminum clad extrusions by Repla
    • Low e, laminated skylights, by Velux
  • Finishes
    • Ecologo gypsum board by Westrock Industries
    • water based, no V.O.C., wood floor sealer by Niagara Coatings
    • interior paint, Lifemaster 2000, Glidden, by ICI
  • Cost: $2.8 million
  • Gross Floor Area: 2480sq.m


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