A Heating Renaissance at Calgary’s Residential Conversion

The Cube, a 52,000-sq.-ft., seven-story building in Calgary’s Beltline neighborhood, features 65 one- and two-bedroom residential rental units and is just a short walk from the city’s downtown area. Once the aging Stephenson office building, the building was converted to new residential and rental units in 2019. The building’s developer, Ash Mahmoud, managing director of Calgary-based Strategic Builders Inc. (SBI), the construction arm of Strategic Group, oversaw the conversion project.

“Cities like Calgary have seen office building vacancy rates as high as 27% in the past few years,” said Mahmoud. “Rather than let downtown buildings go unused, it has been one of our core missions to convert them into residential.”

To conduct the hvac overhaul, Mahmoud turned to Nu-Mun Contracting from Calgary. Working with sbi and the project engineer, David Muncaster, owner of Nu-Mun Contracting, devised a strategy to convert the building to a high-efficiency boiler system and recommended specification of the latest advancement in condensing boiler technology.

Eric Cameron, project manager with Nu-Mun Contracting, oversaw the Weil-McLain Stainless Vertical Firetube (SVF) boiler installation. To meet the building’s heating style and load, the team installed two SVF 1100 MBH high-efficiency condensing gas boilers. The SVF boilers features industry-leading thermal efficiencies up to 97.1%, a clover-shaped stainless steel fire tube heat exchanger for corrosion resistance, and the intuitive and user-friendly Unity control system to simplify installation and operation. The high-water content design of SVF heat exchanger means a low loss header is not required, providing cost savings so the boilers can be piped in a primary-secondary design.

The on-board Unity control system allowed the boilers to communicate with each other. In this configuration, a master boiler controls the modulation and sequencing of the boilers on the network to achieve desired supply temps. “With the automatic sequencing feature, the boilers communicate directly with one another so they sequence themselves and rotate as needed,” said Cameron. “They operate to optimize energy use and efficiencies. When heat is required, the boilers will stage on as needed.”