2015/16 Chapter Winner
Category: Commercial Buildings for an Exciting Facility.
Submitted by, Robin L Smith (He/him)
Reliable Controls
Reliable Controls Headquarters - South Annex, New LEED Platinum Addition to existing building
introduction:
The South Annex consists of two floors of mixed office space and two floors of underground parking and storage, attached to the pre-existing North building. At the beginning of the design process in 2008, the company owners decided to build a LEED® platinum building because it was the ‘right thing to do’ in terms of sustainability, and also to showcase the company’s building automation products as applied to a green building.
The building was completed and occupied in October 2012, housing the R&D, marketing, and accounting departments of the company. The occupied areas are primarily an open office concept, with groups of low partition cubicles and some enclosed management offices. The construction is post and beam, with high ceilings built around a beautiful, central atrium that extends upwards into a third story ‘wind tower’.
Building Specifications
Occupied Area: 1,512 m2
Underground Parking: 2,465 m2
Number of Occupants: 70 (approximately 95% occupied)
Mechanical System Description
Natural Ventilation
In both occupied floors, outdoor air is introduced exclusively by natural ventilation. There are 57 ‘trickle vents’ that open to allow fresh air into the building and add or remove heat as necessary. The air picks up heat and contaminants as it drifts inwards, then upwards into the wind tower. In the summer, the air leaves the wind tower through modulating dampers. In the winter, the air is drawn out by an exhaust fan with heat reclaim.
A packaged rooftop weather station communicating wind velocity and direction to the BAS has proven invaluable in natural ventilation sequences, including as follows:
Only dampers on the leeward sides of the wind tower are opened, allowing the draft created by the wind to draw exhaust air out
On very windy days, the trickle vents on the windward sides of the building are closed temporarily
The ventilation system is also very effective for providing free cooling. For many days in the spring and fall, the hydronic heat/cool systems are completely inactive, with outdoor air providing free cooling for the entire building.
Heat/Cool Hydronic System
Heat is moved around the building by hydronic, not air systems. At the heart of the hydronic systems is a large water storage tank. In the winter, heat is added to the storage tank primarily by two air source heat pumps. During occupied hours, heat is also provided by a water source heat pump that extracts heat recovered from the wind tower exhaust. Hot water from the storage tank supplies 57 trickle vents, 81 radiant floor zones, and 4 small force-flow heaters.
In the spring, summer, and fall the storage tank is switched manually to chilled water storage mode, using the two air source heat pumps as the only source of cooling. Chilled water from the tank is used for the radiant floor zones, six fan coils, and infrequently, for the trickle vents.
Energy Efficiency
The South Annex was designed to use less than 50% of ASHRAE 90.1, 1999. Energy modeling was performed by the mechanical consultant using IES (VE) 2012. The building did not achieve design energy consumption until 2015, the third full year of operation.
Energy Consumption Goal: 234,009 kWh or 58.8 kWh/m2
2015 Actual: 227,087 kWh or 57.1 kWh/m2
As the following chart shows, considerable improvement was made in the first two years.
Indoor Air Quality and Thermal Comfort
IAQ performance exceeds the minimum requirements of ASHRAE 62.1 – 2004. Ventilation effectiveness exceeds 0.9 as per ASHRAE 62-2004.
Twenty-one wall-mounted CO2 sensors were installed, and are used by the BAS to control minimum trickle vent damper position set-points. This allows additional ventilation to be delivered in the specific areas where occupants congregate, such as meeting/conference rooms, and ad-hoc meetings in open areas.
The HVAC systems were designed to deliver comfort as per ASHRAE 55. Occupant surveys to assess satisfaction are planned for the future, to facilitate ongoing improvement.
Innovation
Individual Comfort Control
Each occupant has a desktop ‘widget’ installed on their computer desktop, allowing individual control of occupancy, temperature, light level, exterior sun-shades, and interior fans (not all spaces have all five).
The bottom, right image is the interface for temperature control. Note that the current temperature and set-point are not displayed or adjustable. Occupants select the flame or snowflake icon to register a request for more or less heat, thereby acting as human thermostats! This methodology is particularly applicable to the South Annex, where thermal comfort is achieved mainly from the net radiant exchange between people and surfaces (difficult to measure with a wall-mounted sensor), and where open office space makes it very difficult to provide zone control. For each group of cubicles, or zone, occupant temperature adjustments though desktop widgets are counted as votes, used by the BAS to adjust trickle vent and floor set-points in a democratic fashion.
Trickle Vents
The trickle vent design was a collaborative effort of the mechanical consultant, owner’s staff, and sheet metal contractor. Similar implementations in three other buildings were reviewed, and found wanting. In the end, the trickle vents were custom designed and built by the sheet metal contractor. They consist of a fixed external louvre, modulating damper, modulating single row heat/cool coil, and a fixed interior louvre. Three features set the design apart from other trickle vent designs:
The coil is sealed in a sleeve, so outdoor air must pass through the coil before entering the building.
A condensate pan and drain were included, facilitating chilled water operation.
Several trickle vents on each exposure include interior and exterior air temperature sensors, allowing the BAS to determine if the air flow direction is reversed due to wind pressure, resulting in a temporary closure of the trickle vents on that exposure.
Lighting System
Hallway and miscellaneous lighting consists mainly of LED pot lights with on/off control provided by the BAS. Overhead lighting for all enclosed and open offices is provided by T5 fluorescent fixtures with dimmable ballasts. On/off and dimming is controlled per fixture by the BAS. Each occupant or pair of occupants can adjust the light level set-point for their work space, as measured by an analog light level sensor. A controller in each fixture dims the ballast automatically to maintain the light level at set-point. This method provides daylight harvesting, and also allows occupants to simply turn their lights off if they are not beneficial.
Window Shades
Exterior motorized window shades were provided on all windows with South and West exposure. The window shade motors are controlled directly by the BAS, allowing custom programming, including night closure, thereby reducing radiant heat loss in winter and minimizing light pollution for residential neighbors. Individual occupant controls ensure that the sunshades can be closed during occupied hours if required, to minimize undesirable heat gain and computer screen glare.
Operation and Maintenance
To provide feedback and motivation for continuous improvement, it was decided to create a mechanism for determining and reporting energy performance on a daily basis. A local consultant was hired to provide a calculation method that predicted 50% of ASHRAE 90.1 energy consumption for the South Annex for each day, adjusted for actual heating/cooling degree days. The BAS was programmed with the resulting calculations, and generates daily and monthly charts showing actual versus target energy consumption. This feature proved instrumental in tracking the effect of operational changes.
The above charts are viewable by all employees and visitors on the touch-screen dashboard in the lobby, thereby helping to obtain participation from occupants for individual energy saving activities (turning off computers, reducing lighting set-points, etc.).
Building Automation System (BAS)
Every major mechanical/electrical component was integrated into the BAS. BACNet®
Integrations include 13 variable frequency drives, 7 BTU meters, 12 parkade gas detectors, 1 water source heat pump, 2 air source heat pumps, and 1 card access security system. Modbus integrations include 2 power meters, and 1 weather station. The high level of information provided to the operator by these integrations was essential in identifying and solving start-up problems, and in the process of continuous improvement that will never end!
Cost Effectiveness
The difference between the actual 2015 energy cost and the cost of energy for a building built to ASHRAE 90.1 standards was calculated to be $21,400 (tax included). No attempt was made to calculate the payback for the additional expenditure required to achieve LEED platinum status.
Environmental Impact
Extra effort was put into the design of domestic and rainwater management systems on the site. Rainwater falling on the South Annex is first stored in two, 7.5 m3 cisterns, one used for irrigation, and one used for flushing toilets. Excess water runs into a stream that meanders along the West face of the building, then pools in a bioswale at the bottom of the site, to be absorbed into the ground.
Water efficient landscaping was implemented to reduce the irrigation required by 50% compared to a standard building. A green roof planted with drought-tolerant plants covers an exposed portion of the parking lot. The design concept was that 100% of irrigation could be handled from the cistern.
Potable water used for sewage conveyance was reduced by 82% compared to a standard building. The cistern used for storing water used for toilet flushing is very successful, as it operates in all four seasons. Even in a year of very low rainfall, the flush toilets used 100% rainwater for 8 months. Low flow toilets, waterless urinals, and low flow showerheads and faucets were used exclusively.
The LEED program required that potable water be reduced 20% by excluding potable water use for irrigation. Actual designed overall potable water use reduction exceeded 60%.
No CFCs were used in refrigeration equipment. The main air-to-water heat pumps and water-to- water heat pump used HFC R410A.
