Green life for heritage buildings - 39 Hunter Street, Sydney

Increasingly, existing buildings are being refurbished to meet the requirements of building owners and tenants for improved environmentally sustainable performance.

Older buildings in particular need to upgrade and adapt to meet these changing needs and preferences if they are to compete with newer buildings.

What of heritage buildings? Due to statutory constraints they can be a challenge to refurbish - even without environmentally sustainable credentials.
Significant improvements can be made with minimal cost to any building through housekeeping review, energy purchase, improved maintenance and recommissioning of the building's services.

Challenges include the need to satisfy approval bodies that enough of the original fabric is being retained. The trade off for loss of less significant fabric being the reinstatement of other concealed heritage features and the possibility of high environmental ratings.

Another significant challenge in upgrading the sustainability of heritage buildings is the dearth of building contractors with experience across both fields. Engaging a green building professional is a step in the right direction but alone it doesn't provide 'green' expertise.

Melbourne based Kamirice Pty Ltd purchased the 92 year old building with a aiming to achieve a minimum 5 Star Green Star, 5 Star NABERS Energy Rating (previously ABGR) base building refurbishment.

The building was built in 1916 and occupied by its former owners since then. It had undergone alterations in the 1960s and 1970s reflecting contemporary perceptions of 'desirable' office space. The building is listed on the State Heritage Register and the Register of the National Trust in Australia, and is subject to a permanent Conservation Order.

At the time of purchase, behind the sandstone and trachyte façade (with slate and copper mansard roof features) - the retention of which scored high for both heritage approval and green ratings - little of historic value could be seen internally, with decorative cornices on the high plaster soffits covered by suspended ceilings. Marble cladding to the main staircase and the paneled boardroom remained the dominant features of heritage interest. Natural light ingress to the lower floors was poor, resulting from partial infill of the two original lightwells plus the overshadowing by more recent adjacent buildings.

The level of overshadowing became one of the most analysed aspects of the building. Arup engineers undertook numerous studies to determine the light penetration into the building both in its original form, following the partial infill of the lightwells, and via a proposed atrium in the optimum location to minimise intervention to the heritage structure while maximising light penetration to lower floors. Infilling an existing void at the rear of the premises allowed this cutting through of a dramatic seven story atrium with minimal loss to the net lettable area of 6,300 m2.

It also became obvious that one of the most significant remaining heritage features, although damaged and cut during past 'modernisation works', were the beams and cornices of the original ceilings. To reinstate and retain these features, it was determined that a mechanical ventilation system that allowed the ceiling to remain exposed would be the best fit.

All alternatives were explored to meet ABGR (now NABERS Energy) targets along with obvious reticulation and plant constraints with the preferred technology being an underfloor displacement system. This was relatively innovative for use in a commercial building in Australia and met the objectives of indoor air quality, individual control, flexibility and reduced maintenance. More importantly, using a raised floor plenum left the ceilings exposed and intact.
Jackson Teece architects then developed a custom built 'lily pad' to conceal services reticulation in the centre of each coffer of the intercrossing beams. This had the additional advantage of introducing a material to assist with acoustic control.

Other environmental features of the refurbished building include the use of gas fired generators used to run one of two chillers, as part of a peak load reduction strategy, and innovative use of an insulated sprinkler tank for pre cooled water storage. Rain water will be collected and re-used to flush toilets. All storm water leaving the site is treated and filtered (using a leaf filter).

The refurbished building includes high efficiency luminaires, high frequency ballasts and energy efficient lighting controls. All timber and composite timber products used in the building and construction works were sourced from post consumer re-used timber, or FSC certified timber. More than 95% of all painted surfaces, carpets and adhesives/sealants have been specified to comply with low VOC benchmarks.

The building will provide bicycle storage and showers for tenants and visitors, and a dedicated waste management room.

A major intervention that almost caused controversy with the Heritage Office was the client's commitment to equitable access throughout the building. A wheelchair platform installed in the 1990s served the stepped entry from Hunter Street. To enable ease of access for wheelchair users, the adopted scheme includes a 1:20 walkway (by legal definition, not a ramp) from the street entry to the new lifts which provide access to all floors, including the raised tenancy area at ground floor level. Ultimately, the Heritage Office viewed this 'intrusion' to the structure positively.

Securing approvals through Sydney City Council required a dedicated team effort, with JCK Consulting (Project Managers), Jackson Teece as Project and Heritage Architects working with Arup and Hyder Structural Engineers to determine the best solution for each issue. The substantial intervention into the building was justified in part by the reinstatement of concealed remnant fabric, exposing ceilings and repairing cornices, maintaining evidence of strong rooms where these remain intact, keeping new plant levels back from the heritage façade, and maintaining the façade and mansard roof structure and covering.
There was no doubt too that both the City Council and Heritage office could see the value in the ESD strategies being employed.

Environmental initiatives in this project

Management

• Green Star Accredited Professional engaged from the commencement of the design phase
• 12 month commissioning building tuning period including quarterly reviews and final re-commissioning after 12 months of operation
• Appointment of an Independent Commissioning Agent to ensure optimal building performance
• Comprehensive Building Users Guide
• Environmental Management Plan
• Comprehensive waste management plan to divert 80% of construction waste from landfill

Indoor Environment Quality

• High levels of air change effectiveness and thermal comfort
• Individual comfort control
• Carbon dioxide monitoring and control
• Thermal modeling to optimise comfort levels
• Low-VOC paint, carpet, sealants and adhesives throughout the building

Energy:

• Energy efficiency modeled to achieve an estimated 5 star ABGR rating
• Tenancy sub-metering to enable effective energy monitoring
• Low pressure drop displacement air conditioning system
• Innovative use of the sprinkler tank as a cold store for base building electrical demand reduction
• Gas generator coupled to chillers and pumps for base building electrical peak load lopping
• Energy efficient T5/LED lighting
• Variable speed pumping circuits for increase energy efficiency

Transport

• Secure bicycle storage facilities, lockers and change rooms

Water

• Waterless urinals and 3/6 L dual flush toilets
• Water efficient fixtures
• Rainwater tank for recycling water and stormwater retention

Materials:

• Shell and Core fitout to over 60% of the building
• PVC minimisation
• Re-use of façade and structure
• Use of sustainable timber and re-use of existing timber
• Recyclable carpet tiles
• Use of envirocrete (recycled concrete) and recycled steel

Emissions:

• Low Ozone Depletion Potential (ODP) refrigerants
• Refrigerant leak detection
• On site stormwater retention

Innovation:

• In excess of 25% peak load reduction
• Installation of "lily pad" ceiling system incorporating lighting and fire services