By Daniels Wingerak Engineering
Cameco Operations CentreBuildings Building Mechanical & Electrical (HVAC) Systems
The Cameco Corporation is one of the world's largest uranium producers with four operating mines in Canada and the U.S. To keep up with its rapid growth, the company built a new office in 2009 to accommodate around 300 people. The 3-storey,...
The Cameco Corporation is one of the world’s largest uranium producers with four operating mines in Canada and the U.S. To keep up with its rapid growth, the company built a new office in 2009 to accommodate around 300 people. The 3-storey, 6,500-m2 building is located on 11th Street in Saskatoon.
One of the design criteria was that it should be green and energy efficient. The building is modeled to use 70% less energy than a building built according to the Model National Energy Code for Buildings.
Its actual performance was monitored and the results show an energy intensity usage (EIU) of 0.68 GJ/m2. According to Natural Resources Canada the average EUI for office space in Saskatchewan is 2.02 GJ/m2. This shows that the Cameco building is using 66% less energy than the average office building in Saskatchewan.
In Saskatchewan, achieving economical, efficient heating and cooling building solutions is a challenge for designers. The province boasts some of the largest seasonal variations in the world, as the temperature in the Prairies swings from -40 C to +35 C. There is a long heating season, with a short sharp cooling season, and daily temperature variations as much as 18 degrees C. Precipitation is also an issue, as Saskatchewan is the driest province in Canada, but experiences the highest rainfall intensity.
Integrated design process
Cameco is committed to integrating environmental leadership into everything they do. Consequently, the project team was tasked with designing a building that met all of the form and function requirements in the most sustainable fashion possible. One of the most important steps was establishing an integrated design process. It brought together the architect, structural engineer, mechanical engineer, electrical engineer, interior designer, construction manager, landscape architect and owner to create design synergies that improved sustainability while controlling costs.
For the mechanical systems, the design had to meet Cameco’s sustainability and function requirements, while controlling capital costs.
The selected approach for the building heating, ventilation and air conditioning and plumbing systems combines standard “tried and true” technology with leading edge equipment and systems. The use of new technology required careful temperature calculations and psychrometrics (the science of air temperature and humidity).
Following are some special features of the mechanical design.
Active chilled beams and cooling
The selected terminal cooling and ventilation technology is known as an “Active Chilled Beam.” Active chilled beams are induction devices that use pressurized fresh outdoor air to induce warm room air over a chilled water coil. The high induction nature of the beam also ensures that the relatively low volume of fresh air is well mixed and introduced into the breathing zone of the occupants.
Perimeter chilled beams were supplied with heating coils to provide an additional level of temperature control. At the time of construction, the active chilled beams that arrived on site were some of the first to be installed in North America and the very first in Western Canada. They were also the first beams to be manufactured in Canada.
Chilled water is generated with an efficient air-cooled scroll chiller. The chiller size could be reduced because of the good envelope, window and shading design of the building, and also due to energy-saving features like daylight controlled dimmable lights. Free cooling is obtained from a coil within the primary air handler that generates chilled water when ambient conditions permit.
Dedicated outdoor air and
double wheel air handler
Humidity control is a concern in chilled beam systems as the beams have no ability to remove latent heat – moisture – from a space. As a result the fresh air system is required to dehumidify. For maximum energy efficiency a Dedicated Outdoor Air System (DOAS) with heat recovery was selected to provide fresh air to the active chilled beams. This system is required to provide low dewpoint fresh air into the building for dehumidification, while not over cooling interior spaces.
Typically reheat is used in this application, but cooling air and then reheating with “new” energy is not energy efficient. As a result, a double wheel air handler was selected. The double wheel air handler has a chilled water coil located between a sensible recovery wheel and a total recovery wheel.
In the summer, the sensible wheel recovers energy from the exhaust air stream to reheat the air leaving the cooling coil. The cooled exhaust stream then pre-cools the incoming fresh air through the total energy wheel before it enters the cooling coil. In the winter the system is essentially two recovery wheels and it has a heat recovery effectiveness exceeding 90%. As noted above, this unit also includes a free cooling coil that produces chilled water when ambient conditions permit, while also preheating fresh air. This is the first installation of this type of air handler in Saskatchewan.
The fresh air system serving the active chilled beams was supplied with a large number of pressure independent air valves. These air valves provide “zones of occupancy.” The intent is to allow portions of the building to be shut down when not occupied. The system was designed to operate in areas as small as four workstations without wasting ventilation air into other unoccupied areas.
High-efficiency condensing boilers
Most of the heating for the building is from high efficiency modulating condensing boilers. These boilers feed a heating loop that is blended down in temperature to serve in-slab heating manifolds. In-slab radiant heat has become very popular in Saskatchewan due to its high level of occupant comfort.
Radiant heat also provides two paths for energy conservation. The method of heat transfer warms people directly and as a result they are comfortable at a lower ambient air temperature. A lower air temperature reduces the heat loss of the space through the building envelope.
The second energy advantage is that a low-temperature, high mass system brings low temperature return water to the condensing boilers. Condensing boilers require low temperature return water to actually condense and achieve maximum efficiency. The boiler plant is expected to perform with an efficiency of over 94% year-round. Actual monitored efficiency averaged to 93% over one year of operation.
Controls, monitoring and wireless thermostats
A high performance building requires a high performance control system. A full building DDC system (direct digital controls) was installed with a full graphics package and energy monitoring package. All the building loads are monitored and are viewable. Lighting loads per floor, plug loads per floor, chiller load, and boiler and domestic hot water gas consumption are a few of the monitored energy points.
In addition, a screen is mounted in the reception area that provides real-time charts showing energy usage in the building. The screen allows the occupants to gain a real sense of how their actions impact the building’s energy consumption.
The requirement that the building should be easy to renovate drove another innovation. Wireless thermostats were used throughout, and each thermostat acts as a wireless repeater to create a robust mesh network. For future office renovations the thermostat can be simply moved to a new location and programmed quickly to control the appropriate devices. Nearly every workstation in the building has been provided with a thermostat for individual temperature and occupancy control.
Solar hot water and water conservation
Evacuated tube solar coll
ectors were installed on the roof to provide supplementary heating for the domestic hot water system. The solar panels preheat storage tanks that feed a condensing natural gas storage hot water heater.
An evacuated-tube collector contains several individual glass tubes, each containing an absorber plate bonded to a heat pipe and suspended in a vacuum. The vacuum is an ideal insulator and allows high levels of heat transfer even at exceptionally low outdoor temperatures. The pipe transfers the heat efficiently to a condenser through the top of the tube.
Heat transfer from the absorber to the fluid circuit is performed by the “heat pipe.” A heat pipe is a closed system, evacuated and charged with a small amount of water before it is sealed. The absorber imparts heat to this water, causing it to evaporate. The steam rises to the upper end of the heat pipe where it transfers heat to the fluid circuit via a metallic conduction bridge. Being a “dry” connection, fluid in the heating circuit does not flow through the collector.
High and ultra-high efficiency plumbing fixtures used throughout include the first ultra-low flow urinals installed in Saskatchewan. These urinals use only a half litre of water to flush – 90% less than a standard low-flow urinal.
The landscape irrigation systems are also low and ultra-low flow. The controller is connected to remote weather stations to prevent watering on rainy days.
The domestic water system was designed to use 56% less potable water than a standard office building, saving 800,000 litres per year of water. In actual operation the building is using nearly 80% less water per square metre than the other office space that Cameco owns.
Performance and cost
Life cycle costing was considered in all aspects of the design. As well, the careful integration of the design features enabled savings such as a smaller boiler and chiller plant.
Despite tendering the project during an unprecedented construction boom, the building was built on budget and within the rapid time frame required by the owner; design and construction were combined in 18 months.
The energy savings reduce potential greenhouse gas emissions by over 510 metric tons per year, equivalent to removing over 100 cars from the road. cce
Client: Cameco Corporation
Mechanical design: Daniels Wingerak Engineering, Saskatoon (Christopher Conley, P.Eng.)
Prime consultant: Kindrachuk Agrey Architecture
Electrical: PWA Engineering
Structural: Robb Kullman Engineering
Construction manager: Graham Construction and Engineering
Suppliers: Twa Panel Systems (chilled beams); Harsco Industrial Patterson-Kelly (boilers).