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Telus Corporate Offices

Image 1: Telus Corporate Offices

Figure 2: Facade Ventilation Operable Window with Fritted Glass

Building Design Features

Underfloor Air Distribution System Characteristics

UFAD System Performance

Vancouver, BC


eight-story 11,800 m2 (127,000 ft2)

Construction Status:
Occupancy started in fall of 2000.

Building Use:
A retrofitted telecommunications utility local services center and utility executive offices.

Design Team:


Telus Corporation


Busby & Associates Vancouver

Mechanical design:

Keen Engineering


Dominion Construction Vancouver

Building Design Features

This project involves a major retrofit of corporate offices for the British Columbia telecommunications utility. The building is a multistory concrete structure that is being retrofitted to be highly energy efficient. This project contains a number of unique features. Seven floors with 930 m2 (10,000 ft2) floor plates have been retrofitted with UFAD systems. Each floor is served by its own air handling system. Concrete exterior walls retain refurbished existing single glazed wood frame double hung windows. What may be the first example of large scale ventilated facade technology has been installed on the face of the building as shown in Figure 1. The double-glazed facade uses fritted glass to reduce the higher angle solar gain (the light stripes shown in Figure 1). Occupants look horizontally through clear glass but when they look up they see the fritted glass. Windows in the facade are operated by the occupants via switches in the room.  Facility personnel can override these controls as well as the dampers and fans in the cavity. The dampers at top and bottom as, well as exhaust fans at the top, are powered by a photovoltaic array. The dampers and fans are controlled by a series of temperature sensors located at several places in the cavity. The dampers and fans are operated to allow ventilation in the summer and insulation (all openings closed) in the winter. These features are anticipated to reduce both heating and cooling loads dramatically, but still allow occupants to control ventilation to their space.

The inside layout is open plan although the interior of each floor has several enclosed meeting rooms. Each floor has multiple separate office spaces accessible via a central hallway. Floor access and service areas are located in the interior. Modular furniture from a variety of manufacturers with movable partitions is used throughout. The raised floor panels mounted on a stringer-less post system provides for a 0.45 m (18 in.) plenum; floor panels are covered with glued down non-coincident carpet tiles, 0.61 m x 0.61 m (24 in. x 24 in.).Ceilings are open, white painted exposed concrete 4.5 m (15 ft) high with suspended direct/indirect fluorescent lighting fixtures and exposed sprinkler lines. Workstation telecommunications and electrical wiring are provided by an access module mounted in the floor panel, which is in turn connected to a junction box in the plenum with 3.7 m (12 ft) whips.


Underfloor Air Distribution System Characteristics

Design Intent
This retrofit project was inspired by Telus team members who believed in green and sustainable design and that the leading edge nature of telecom business should be reflected in the work environment. Since Telus is a telecommunications utility, flexibility in reconfiguring spaces and accommodating telecommunications services was highly desirable. An UFAD system was conceived as an integral part of a high quality indoor environment and an energy efficient solution to space conditioning.


Plenum Height: 0.46 m (18 in.)
Diffuser Types:

Krantz swirl diffusers are used for all interior and perimeter areas.

Raised Floor: 0.61 m (24 in.) wood-core panels using a stringer-less post mounting system were supplied by APS Access Floors.
Supply Air Temperature:

Nominal 17°C (63°F), varies with load

UFAD System Types: Constant air volume – variable temperature (CAV-VT) for delivery to the space; variable air volume (VAV) at air handler (see below).

The system depicted in Figure 3 has a number of unique design features. Each floor uses a dedicated air handing unit (AHU) that supplies conditioned air directly to the underfloor plenum with very limited distribution ductwork. The AHU is fitted with a variable speed drive to maintain constant pressure for interior zones. The perimeter system uses a series of fan coil units (FCU), each of which is fitted with a mixing damper arrangement that allows the unit to supply variable temperature air to the perimeter swirl diffusers. These units are connected to space return air ducts that draw warm air from the ceiling area as needed. A hot water heating coil augments the re-circulated air to provide heating. The hot water for these coils is furnished by waste heat from a nearby process waste heat stream, virtually eliminating the use of fossil fuel for heating.

The operation of this system is divided into two main elements. In the perimeter, zone temperature sensors control the fan coil mixing boxes by first modulating the mixing dampers and then the reheat coil control valve when the dampers are in full re-circulation mode.  This results in CAV operation of the perimeter system as a standalone system. The interior system floor diffusers are operated as a CAV-VT system by varying the supply air temperature of the AHU in response to demand from interior zone temperature sensors.  Due to the fact that the perimeter system has a variable demand on the plenum air supply depending on its mixing state, the central AHU is operated as a VAV system to maintain constant pressure in the underfloor plenum.


UFAD System Performance

Although this building was reviewed during its construction before occupancy, feedback from the designers and the owner’s representative confirms that there is a high degree of satisfaction with the UFAD system. Occupant control of local comfort conditions via adjustable floor diffusers and operable windows have been cited as key factors in user satisfaction; “it just has a nice feel to it.” The use of fossil energy for heating has been eliminated due to use of process waste heat for perimeter reheat coils.

CBE Findings
(These comments reflect the views of CBE researchers based on a limited study of the building and do not necessarily represent those of the designers and/or owners.)

Churn for the groups occupying this building will be high; estimated at 50-75%.

The open concrete ceilings have resulted in a “harsh” acoustic environment; steps are being taken to improve the acoustic performance.

During initial occupancy and commissioning there were imbalances in the air distribution and a noticeable difference between the interior and perimeter air flow rates. The balance issues have been resolved and the occupants have also learned that moving or adding floor diffusers in their local area can address their air flow and comfort problems.

This system is a unique and interesting solution in that it maximizes the opportunities to save energy while maintaining good performance on the airside. Although the perimeter system uses fan energy from relatively inefficient small motors, it minimizes reheat due to the mixing system and by drawing air from the ceiling area. In addition, VAV operation of the central AHU will tend to reduce fan power requirements to some extent.

Using constant volume solutions for the perimeter and core areas ensures operation of the floor diffusers at their optimum design point.

The perimeter mixing system combined with the process waste heat hot water supply, and the load reduction afforded by the glass facade should result in extremely low or no fossil fuel use for heating.

Cooling energy use should likewise be reduced due to operation of the ventilated façade in summer. However, the use of the operable windows may cause problems with air and pressure balances for the AHU.

Since distribution ductwork has been eliminated, the designer anticipates using relative high static pressure 25-37 Pa (0.10-0.15 in. w.c.) to provide air distribution. However, this may result in excessive leakage unless care is taken to seal floor panels and interfaces between floor and other building components.

Elimination of supply air ductwork in the plenum reduces system first cost. However, the return air duct chases that allow air to be drawn from the ceiling area into the perimeter FCUs add to cost. Overall we would expect this system to be on par with other similar solutions with regard to first costs.

Date Reviewed: February 2000 – April 2001

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