Depot’s Green Star design and how to get greener over time
ALAN DAVIS, associate and Sydney team leader of WSP Built Ecology, shares how Sherwood Road Bus Depot achieved the first five-star Green Star Industrial Design v1 rating, and reveals some quick-win retrofit opportunities that can be incorporated in existing facilities.
Sherwood Road Bus Depot, located in the suburb of Sherwood in Brisbane, Queensland, is the first industrial development to achieve a five-star Green Star Industrial Design v1 rating in Australia. Not only did the client, Brisbane City Council, and the development team take up the challenge of being the first five-star Green Star rated industrial building, but the nature of the development itself posed real hurdles in delivering this sustainability ambition.
This article presents the integrated design solutions that were incorporated in the development, which address energy consumption, greenhouse gas emissions, potable water consumption and the future proofing of the development against uncontrollable utility and climate change elements. The article also identifies some quick win retrofit opportunities that facility managers may be able to incorporate in their existing facilities.
NOVEL STORMWATER STRATEGY SEES OPERATIONAL SAVINGS
As the site is a bus depot, a significant area is allocated as hardstand; for example, the bus and car parking, and the access road. This area is far greater than what would typically be seen in other types of industrial rateable projects, such as warehouse distribution buildings, which are predominantly building area-based. The roof catchment and impermeable bus hardstand catchment areas made achieving the stormwater credit much more challenging; however, two points were achieved through an innovative water-sensitive urban design stormwater collection and pre-treatment strategy.
Stormwater run-off from bus hardstand areas is drained into vegetated swale medians between the parking bays, which form a landscape filtration corridor network. Each swale collects stormwater run-off into field outlets at the low point of each swale, which is then conveyed via conventional drainage to a 150-kilolitre underground stormwater reuse tank.
High flows are diverted from the tank to a bio-retention basin for further pre-treatment prior to discharge to Oxley Creek to a quality that allows for discharge to a natural watercourse, removing nutrient and hydrocarbon pollutants through effective passive biological pre-treatment.
Landscape irrigation calculations demonstrated that the 150-kilolitre tank capacity is sufficient to meet 93 percent of the non-potable water demands, exceeding the 90 percent requirement necessary for Green Star.
Stormwater run-off from the roof catchment areas drains via a conventional gravity piping system to a separate 250-kilolitre underground rainwater reuse tank. From there, the non-potable supply is filtered for suspended solids, sanitised via UV sterilisation and pressurised for reticulation to all site amenities for the supply of sanitary flushing.
The potable water consumption of the development, based on the application of efficient ﬁttings and ﬁxtures, and rainwater harvesting, is calculated to be 71 kilolitres per week (derived from the applicable Green Star calculator tool). A reference development would typically consume 124 kilolitres per week. Applying a bulk water rate, annual savings are estimated to be $3000.
In addition, a 42 percent reduction in Portland cement use is predicted for the project. Given the quantity of concrete on the site, this represents a real environmental benefit in terms of the embodied energy avoided.
DEPOT’S DESIGN ENSURES LOW ENERGY AND GAS COSTS
The building design also incorporates the following integrated design features:
- mixed-mode air-conditioning in the depot office to reduce reliance on mechanical air-conditioning
- natural ventilation in the maintenance garage to eliminate reliance on mechanical air-conditioning
- solar hot water heating to meet a proportion of the domestic hot water demand with a renewable energy resource
- sophisticated lighting controls to reduce lighting demands
- water and energy metering and sub-metering to support monitoring and targeting, and
- sustainable materials selection, including recycled concrete and steel, reduced PVC use and sustainable timber to reduce the environmental impact of resource consumption.
The application of the mixed-mode systems, passive design and HVAC solutions, and sophisticated lighting controls demonstrated that the development should consume less than half the energy of a reference development (derived from the applicable Green Star energy modelling protocol).
The total predicted electricity savings is circa 350 megawatts per hour per annum. Applying typical electricity tariffs, annual savings are estimated to be $50,000. The total predicted gas savings is circa 260 megajoules per annum. Applying typical gas tariffs, annual savings are estimated to be $6000.
GAINING GREEN SAVINGS AT EXISTING INDUSTRIAL FACILITIES
In the context of existing industrial facilities, the integrated design feature that offered the best ‘bang for the buck’ for Sherwood Road Bus depot was the application of daylight controls (photocell sensors) to the lighting system serving the maintenance garage (see Figure 2). When combined with extensive roof lights, this system provided the greatest benefit in terms of electricity consumption reductions (circa 20 percent of the electricity savings defined).
Typically, the installation of DALI or CBUS lighting control systems will mean an uplift of approximately 15 percent in capital expenditure (CAPEX). However, a simple payback period of three to five years is achievable against this CAPEX. Over the life of the system, this will result in significant utility cost savings.
This should be seriously considered as part of any asset replacement cycle (where the facility supports adequate daylight provision to realise the benefit), as it offers a quick win in terms of driving down electricity consumption and reducing operational expenditure (OPEX).
As with all complex systems, for instance mixed-mode air-conditioning, constant monitoring of operational performance against predetermined levels is required to ensure operation is as intended and is performing at maximum efficiency; for example, lighting control sensors are functioning correctly and occupants are not overriding the natural ventilation mode.
This typically denotes the provision of adequate metering and sub-metering with building management system data logging and warning systems. In existing industrial facilities this can be cost-prohibitive. To avoid this cost, facility managers should look to simplify systems or merely replace old equipment with new. They can also consider bringing asset replacement cycles forward, considering payback periods and potential savings over the life of the system.
Facilities managers should also look to remove the need for monitoring through the provision of spaces that respond directly to the occupants’ needs. Install simple, occupant controlled systems and educate the users as to their appropriate use.
SHIFT YOUR THINKING
Sherwood Road Bus Depot has been able to demonstrate through Green Star Design certification that industrial sites can achieve high environmental outcomes through sustainable design. In terms of existing industrial facilities, simple retrofit opportunities exist that, if building owners and operators can look beyond CAPEX, can deliver real savings over the life of the systems. A shift needs to be made from short-term thinking to medium- and long-term thinking in order to realise a greener industrial sector.
SAVINGS GAINED THROUGH SHERWOOD BUS DEPOT’S GREEN DESIGN
Water-sensitive urban design stormwater collection and pre-treatment strategy:
- $3000 per year in water
Mixed-mode systems, passive design and HVAC solutions, and lighting controls:
- $50,000 per year in energy
- $6000 per year in gas
QUICK-WIN RETROFIT SOLUTIONS FOR EXISTING FACILITIES
Quick-win retrofit solutions for existing industrial facilities include:
- changing light fittings
- applying film technology to glazing to improve performance (typically $65 per square metre with simple payback periods ranging from four to 15 years, depending on the HVAC system and extent of glazing)
- increasing roof reflectivity (for example, the application of heat reflective coatings to roofs)
- following preventative maintenance regimes for existing equipment to ensure optimal performance
- improving the energy efficiency of process equipment (for example, assessing opportunities for heat recovery), and
- improving systems design based on good practice, including the application of economisers, assessing opportunities for night-time purge ventilation where diurnal temperature swings allow and scheduling for occupancy with setback temperatures.
Alan Davis moved to Sydney from London in early 2011 to lead the Sydney Built Ecology Team. His extensive exposure to UK-based built environment rating tools has facilitated a ready changeover to the equivalent Australian tools. Davis’ team is currently leading the NABERS monitoring role for WorldPark, Adelaide, was intrinsic in delivering the five-star Base Building NABERS Energy ratings for Sydney Water’s Parramatta head office and the Potts Hill operational headquarters, and developed the Green Star monitoring tool for the Melbourne Convention Centre to track its performance against the six-star Green Star benchmarks for reporting under the relevant state government authority requirements.