Dedicated to sustainable,
high performance building

Clarendon Semis

A residential semi-detached urban infill on a small east/west-oriented lot, with each living unit having three bedrooms plus study and attached garage, is a typical redevelopment in an established Ottawa neighbourhood. With one unit retained by the Developer/Owner/Architect and the other sold at market price, the project was a careful experimental blend of the sustainability preferences of the Owner versus market pricing realities.

By Gordon Erskine



Although the market prefers double garages, this would have resulted in the loss of the existing mature deciduous street trees and forced a three-storey design in an area of two-storey houses. Keeping the mature trees meant going with a single garage.
The home was constructed with insulated concrete form walls [ICF] from foundation footings to the roof trusses. Materials were selected to maximize indoor air quality: floor finishes are entirely hardwood and porcelain tile; plywood was used for subfloor and roof sheathing, and cabinets are solid wood; paints are low-VOC water based; and counter tops and window sills are natural stone.
Construction was completed without a single garbage container on site. Engineered floor and roof trusses were delivered from the factory and generated no on-site waste. Footing forms were reused as scaffolding walkways for the ICF construction and as safety guards. On site paper/cardboard, plastic, metal and organic recycling containers were utilized. Drywall waste was taken to a recycling facility. The biggest challenge was recycling foam from the off-cuts of the ICF system, and the packaging for primarily electrical, plumbing and appliances.

The design of the semis was motivated by:

  • minimizing heating/cooling costs
  • reducing life cycle costs through maintenance-free materials
  • minimizing water and electrical consumption
  • minimizing waste during construction

A high-performance building envelope, simple solar orientation and shading, and the use of natural ventilation were the first steps in meeting these goals. On the more active side, we used heat recovery ventilation [HRV], waste hot water heat recovery, Energy Star appliances, high-efficiency mechanical systems, web-enabled thermostat, on-demand [tankless] hot water tank [HWH], low-flow plumbing fixtures, and energy-efficient lighting [CFL/LED].
Preliminary scoring suggested LEED Platinum for Homes would be very achievable. Walkscore: 75.


  • Nudura insulated concrete form [ICF] system from footings to roof, and under basement slab; also serves as the air barrier
  • Blown fiberglass insulation in attic
  • Sidings are factory-finished wood composite panels, stone veneer and corrugated steel siding
  • Gas furnace operating from an Ecobee web-enabled thermostat, heat recovery ventilator
  • On-demand [tankless] hot water heater
  • Waste water heat recovery pipe
  • Millwork consists of  “no-added” formaldehyde products


  • Architect Erskine Dredge & Associates Architects Inc.
  • General Contractor R.K. Porter General Contractors Ltd.

Gordon Erskine is a partner in Erskine Dredge & Associates Architects Inc., Ottawa.