By Tom Watson, CBCL, and Keith Robertson, Solterre Design
TIGHT ON ENERGYBuildings Environmental Building Mechanical & Electrical (HVAC) Systems Environment
TIGHT ON ENERGY
TIGHT ON ENERGY
he Valley Waste Resource Management (VWRM) Administration Building in Kentville, Nova Scotia is a showcase for sustainable design. One of the first Passive House-certified buildings in Canada, it is the first office building in Canada to be certified by this international standard. The building uses an array of recycled and reused materials and less than one-third of the energy of a typical office building in Atlantic Canada.
The Passive House energy standard originated in Germany as “PassiveHaus.” It is a rigorous voluntary energy standard that dramatically reduces the energy requirements for a building. The building must have a heating requirement of no more than 15 kWh/m2 per year and an air infiltration test of no more than 0.60 air changes per hour — 60% lower than the well-known R-2000 standard.
A more accurate translation of PassiveHaus would be “Passive Building.” The standard goes far beyond residential buildings and has been used to certify commercial, institutional, industrial and educational buildings internationally. The design team and owner of the VWRM building collectively decided to use the PassiveHaus standard, in addition to LEED, believing that it would reinforce the intent to create an exceptionally low energy building. (The VWRM building was certified under the U.S. Passive House Institute. Today in Canada the standard is now administered by the Canadian Passive House Institute.
An energy simulation, verified by a third party, predicted energy savings at the building of over 50% compared to an equivalent building that complies to the ASHRAE 90.1-2007 energy code. The result provides a score of 19 out of 19 LEED optimize energy efficiency points without any contribution from renewables.
The building architect is Solterre Design. CBCL provided mechanical and electrical building engineering, energy simulation, LEED consulting and commissioning.
Orientation, form and envelope
Located in an industrial park on the west side of Kentville, the building lies adjacent to the VWRM sorting and recycling depot. The depot processes general household and business waste from 83,000 residents and 38,000 households throughout the Annapolis Valley region. VWRM represents one of five waste management regions in the province.
The administration building contains offices for staff and also serves as the meeting place for the VWRM Board. The building is the main point of contact with the public and serves as a focal point for facility tours.
The site has excellent solar exposure to the south, and views to the Annapolis Valley to the north.
The design team paid particular attention to the building mass, orientation, and high performance envelope as key passive energy measures. A north-facing slope allowed for a two-storey scheme, with an earth berm on the south side, and grade-level access at both floors.
A hip roof with a clerestory dormer on the south side allows passive solar heating and daylight into the central open office space. Daylight is provided to all spaces. The wood truss roof, supported by a steel frame, has ample depth for the R-96 cellulose insulation.
Materials were selected with a mind to energy performance, environmental performance, low maintenance, and durability. The VWRM Authority was also interested in materials that would showcase its role in recycling and waste reduction, such as salvaged doors, hardwood, hardware, and recycled bottle glass, recycled tires, gypsum board and steel.
The project tendered in the summer of 2011 with multiple bids significantly under budget, and was completed on time in 2012.
By creating a building that would be recognized as a showcase for environmental sustainability Valley Waste Resource Management set out to develop a facility that reinforces the environmental stewardship part of their mission.
Dramatic energy savings
The Passive House standard was used as a guide and target for maximizing energy efficiency and points under the LEED optimise energy efficiency credit. Passive House uses an early energy simulation and sets specific limits on energy use as follows:
• Maximum of 15 kWh/m² annual space conditioning energy.
• 120 kWh/m² total source (or primary) energy consumption, including total electricity.
• Airtight building envelope, air tightness <0.6 ACH @ 50 Pa (approx. 0.1 cfm per square foot @ 50 Pa), third party verified.
• Balanced, highly efficient mechanical ventilation system (>80% efficiency), and a minimum of 30 cubic metres of fresh air per person, per hour. The VWRM project exceeded this ventilation rate in order to meet and exceed the minimum requirements of ASHRAE Standard 62.
To achieve the targets the building’s design team used:
• Superinsulation. Slab-on-grade insulation of R27 (high density extruded polystyrene EPS), foundation walls R34 (insulated concrete forms, with additional EPS and mineral wool), above-grade walls R50 (mineral wool in wood framing with 9″ thick EPS structural insulated panels), roof R96 blown-in cellulose recycled newspaper insulation, and triple glazed windows at between R3.6 to R5.1. Thermal bridging was minimized, including in the fibreglass insulated window frames, so that these thermal resistance values represent the overall resistance to heat transfer of the building assembly.
• Measured air tightness of 0.42 Air Changes Per Hour (ACH) at 50Pa in the initial test and a final test value of 0.33 (ACH). This exceptional performance is from the careful selection of high performance windows and doors, and from rigorous attention to detailing the air barrier — especially at connections and penetrations. The walls use a continuous air barrier of oriented strand board with taped seams. The barrier is located outside the stud framing so it is not interrupted by electrical penetrations.
• Air source heat pump (ASHP), variable refrigerant flow (VRF) heating/cooling system. The ASHP consists of a single nominal 10-ton refrigeration capacity outdoor compressor/condensing unit connected to eight individual indoor wall and ceiling mounted fan coil units. The heat pump system is a full heat recovery type, allowing for simultaneous heating and cooling on a zone by zone basis. In this way the building’s server room or spaces on the south side can be in cooling mode when the spaces on the north side need heating. The heat removed from areas requiring cooling is effectively “moved” to the areas requiring heating, resulting in much lower compressor energy use.
• 90% efficiency thermal mass type heat recovery ventilation (HRV) unit. The HRV is a regenerative “push/pull” type of system where the fresh air drawn into the building and the exhaust air removed from the building is cycled through heat sinks. So in each 60-second cycle one heat sink is being heated by the warm exhaust air, while the other is giving up its heat to the cold fresh air coming in directly from the outside.
• Mixed mode natural ventilation system. A natural ventilation mode for the building consists of operable windows throughout the facility. High level windows in the dormer clerestory are operated by electric actuators. The building’s direct digital control system senses when the interior temperature is above the heating set point (i.e. the heating is off) and the outside temperature is cooler than the inside temperature. In this event the system illuminates a green “natural ventilation” lamp in the main open office area which alerts the occupants so that they can disable the air conditioning at their ASHP thermostat and open the windows to be comfortable without the need for any cooling energy consumption. In this mode a system of actuated dampers ensures that exhaust air is still drawn from the washrooms, and the lower l
evel of the building is still mechanically ventilated. But mechanical ventilation is cut off from the upper level of the building, further saving energy by reducing the fan power.
• LED and high efficiency fluorescent lighting is used throughout, along with automatic controls for occupancy, time clock and daylight dimming. A wireless control system was also used to limit the cost associated with wiring the various lighting control devices. Standalone exterior LED solar lighting was used in the parking area.
Actual performance so far
The total energy use of the average Canadian office building is 333 kWh/m². The actual energy use in the VWRM administration building during the first year of operation, was less than 90 kWh/m²/year. Post construction monitoring and ongoing adjustments to the control systems and building operations are expected to further reduce energy consumption, with the goal of getting much closer to the 44 kWh/m²/year predicted by the Passive House energy simulation, or the 56 kWh/m²/year predicted by the third party-verified LEED energy simulation.
It is anticipated that the reasons why the building has a higher energy use than what was predicted by the simulations are: higher process energy use in the server room and by office equipment; longer building operating hours; and perhaps a lower than predicted use of the natural ventilation system.
The dramatic heating energy use reduction is a function of the super-efficient HRV, air source heat pump system, and the fact that conductive heat loss and uncontrolled infiltration have been almost eliminated by the building envelope design. Fan energy savings are a result of very efficient fans in the small individual fan coil units and a control strategy that switches the fan coil unit fans based on building heating and cooling loads, not occupancy. This approach is acceptable as the ventilation air is supplied independently and directly to the space.
The plumbing fixtures were selected for their water conservation characteristics and reliable performance. The average water consumption for BOMA Best certified buildings is 0.98 m3/m2; the baseline water consumption target calculated for this building’s LEED application is 0.12 m3/m2. The water consumption prediction for the VWRM building, calculated using the LEED method is 0.07 m3/m2.
Recycled, salvaged and re-used materials
Since VWRM’s primary activity is the collection and disposal of waste, the owner was motivated to have the building exhibit the potential for recycled and salvaged materials to be used in new ways. Following are a few examples of how this was achieved.
Tire Derived Aggregate.
Nova Scotia is a world leader in developing a 100% post-consumer aggregate from used vehicle tires. The VWRM project used Tire Derived Aggregate (TDA) as a replacement for traditional backfill materials. TDA helps to solve the problem of what to do with old tires, but also it has a thermal resistance value of R5 per foot, increasing the building’s insulation value. TDA also drains well, helping to keep the building’s foundation dry.
Environmental concerns for TDA tend to centre on TDA in water or saturated soils, and in elevated temperatures. The TDA used as backfill in this case is in a low moisture and temperature environment. No special measures were taken except to surround the TDA with a geotextile fabric.
Post-consumer recycled glass.
The concrete floors at the VWRM building incorporate post-consumer glass as an aggregate, creating an attractive exposed floor that showcases this innovative use of old glass.
Asphalt and shingles.
Asphalt used for the building parking areas was made from recycled sources, as were the roof shingles. The outdoor furniture was made from recycled post-consumer plastic bags.
Recycled newspaper for insulation.
The R-90 roof is filled with 8,000 cubic feet of cellulose insulation, made in Nova Scotia from recycled newspaper.
Salvaged and reused materials.
Inside the building, salvaged and reused construction materials were used for doors, wood paneling and interior windows.
As of July 2014 the building has been submitted to the Canada Green Building Council for evaluation under the LEED Green Building Rating System and is in the first review stage. cce
Owner: Valley Waste Resource Management Authority
Architects and LEED consultant: Solterre Design (Keith Robertson, Jennifer Corson, David Gallaugher)
Mechanical and electrical engineer, energy simulation and commissioning: CBCL (Tom Watson, P.Eng., Darryl Kasun, EIT, Tim McLeod P.Eng., Jared Smith, EIT, Matthew Rodgers, P.Eng.)
Civil/structural: Sherwood Enterprises
Passive House consultant: Passive House E-Design
Project management: Gantline
General contractor: Roscoe Construction
Supplier: Tempeff (HRV)