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Image 1: Telus Corporate Offices
2: Facade Ventilation Operable Window with Fritted Glass
Building Design Features
Air Distribution System Characteristics
eight-story 11,800 m2 (127,000 ft2)
One floor occupied in fall of 2000.
A retrofitted telecommunications utility local services center and
utility executive offices.
& Associates Vancouver
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)
Air Distribution System Characteristics
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.
m (18 in.)
swirl diffusers are used for all interior and perimeter areas.
m (24 in.) wood-core panels using a stringer-less post mounting system
were supplied by APS Access Floors.
17°C (63°F), varies with load
air volume – variable temperature (CAV-VT) for delivery to the space;
variable air volume (VAV) at air handler (see below).
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
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
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.
(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
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
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