Active chilled beams greatly improve energy efficiency

130 Stirling Street is one of the first buildings in Perth to attain a 5.5 star rating under the National Australian Built Environment Rating System (NABERS) without using GreenPower.

When Charter Hall Group developed the building, it committed to a 4.5 star NABERS rating. A Western Australian Commitment Agreement is a contract between the NABERS Regional Administrator, the Public Utilities Office and a commercial office building proponent who commits to design, build and commission the premises to achieve a 4 star or higher NABERS Energy rating. This allows the building proponent to promote the desired rating. The contract typically spans a number of years and remains in effect until the building has received its benchmark NABERS Energy rating, after the first 12 months of operation. The agreement encourages design consultants, project managers and building owners to focus on achieving the agreed performance target through all phases of a new development or refurbishment.

The seven-level building incorporates active chilled beam air conditioning, efficient lighting and a central atrium which greatly reduce energy consumption while also providing a comfortable working environment.

“The biggest energy savings are due to the chilled beam air-conditioning system. Chilled beams are t-shaped steel beams that have chilled or heated water piped through them. The beams (which are effectively heat exchanger coils) cool the air around them, the cool, dense air then falls to the floor, warm air rises, is cooled and a constant circulation of chilled air flow is created. Much like radiant heat, this convection method is more comfortable than traditional fan-driven air-conditioning systems as, even where fans are used, the velocities are lower so there isn’t the breeze that can generate many complaints from staff sitting closest to the air-conditioning outlets. The temperature is also more consistent throughout the floor plan. Most importantly the chilled beam system requires much less energy to operate than other more-traditional air-conditioning systems.”

The energy efficiencies start from the outside in. The developers and architects built comprehensive shading structures to keep direct sunlight off the windows for most of the day. The building is therefore not subjected to the solar loads that can send energy consumption soaring.

Inside the seven-level building a central atrium acts as a light well, bringing natural light right into the four office floors. This reduces the need for artificial light and creates a more comfortable environment for tenants.

Charter Hall has an experienced property management team involved in the management of 130 Stirling Street. By working in a collaborative way with the main energy consultants, HFM Asset Management, the air-conditioning contractors and the building facility managers, the team have been able to achieve the high NABERS rating but also maintain a comfortable environment for the tenants. The continuous monitoring of all meters and monthly reviews assist in maintaining the high NABERS rating. 

This continuous monitoring of the building’s operation means any anomalies or spikes in energy use are picked up in the monthly reporting system and addressed as soon as possible. The property management team also introduced start and stop time capabilities for all systems to ensure plant and equipment is only operating when needed and put in place a premium maintenance regime to keep the air-conditioning systems in optimum condition.

Charter Hall, along with its consultants, is also investigating automatic lock-out periods for the cooling and heating systems, so that when a certain temperature is reached (low or high), there is a time lag before the opposite system kicks in - this prevents the heating and cooling systems from ‘fighting it out’. Charter Hall’s Head of Asset Management - Office and Industrial, Craig Newman, said: “It is through a focused, proactive and collaborative approach in managing 130 Stirling Street that we have been able to outperform our stated sustainability benchmarks for this property year on year. This is a great achievement for our tenants, the building and the entire team who have worked and continue to work on the building.”

Graham Postma from Savills, the leasing agent on the project from its inception, supported Newman’s comments, stating: “From a tenant’s perspective, every dollar saved in energy charges goes directly to the tenants’ bottom-line profitability, and if these savings are achieved while ensuring maximum tenant comfort and productivity the benefits are even greater.”

The energy efficiency - and therefore cost benefits - of moving to a new CBD fringe project include large efficient floor plates, lower occupancy costs and environmentally sustainable design (ESD) standards required by government and corporate tenants.