HVAC Design for Heritage Buildings

What You Need to Know

Heritage buildings need air conditioning too. The challenge is installing modern HVAC systems without damaging the fabric that makes the building significant. In NSW, any work on a State Heritage Register item requires approval under the Heritage Act 1977, and the design must follow the conservation principles in the Burra Charter. The NCC still applies, but a Performance Solution is often the only viable compliance path because heritage constraints prevent standard Deemed-to-Satisfy designs.

VRF systems with small-diameter refrigerant pipes are the most common solution. They need less space than ducted systems, cause less disruption to heritage fabric, and can serve multiple zones from a single outdoor unit hidden at ground level behind the building.

• NSW Heritage Act 1977, Section 57 prohibits works on State Heritage Register items without approval from the Heritage Council of NSW. This includes installing new HVAC systems, running ductwork, and mounting external equipment. A Section 60 application is required for new mechanical services installations.
• Standard Exemption 5 allows repair, replacement, or removal of existing non-significant services (including mechanical ductwork and equipment) without a full Section 60 application. Does not cover new installations or work that affects significant fabric.
• Burra Charter 2013, Article 15 requires that change to a heritage place be guided by its cultural significance. Changes that reduce significance should be reversible. HVAC installations must be designed so they can be removed without permanent damage.
• Burra Charter 2013, Article 22 states that new work must not distort or obscure the cultural significance of the place. Visible equipment, grilles, and ductwork on significant facades or interiors will be rejected.
• NCC Performance Requirements for ventilation, thermal comfort, and energy efficiency still apply to heritage buildings. Where Deemed-to-Satisfy provisions cannot be met due to heritage constraints, a Performance Solution under NCC Clause A2.2 is required. Performance Solutions need supporting evidence from a qualified engineer.
• AS 1668.2:2024 sets minimum outdoor air rates for mechanical ventilation. Heritage buildings must still meet these rates. The standard applies regardless of building age or heritage status.
• Local heritage items listed under a council's Local Environmental Plan (LEP) require development consent for HVAC works. The approval process is less onerous than State Heritage Register items but still requires a Heritage Impact Statement. Check the relevant LEP heritage schedule and associated Development Control Plan.

The first step is always a heritage assessment. Before any HVAC design starts, you need to know what is significant and what is not. A heritage consultant maps the significance of every element: walls, ceilings, floors, mouldings, and existing services. The HVAC design then works around the significant fabric. Non-significant spaces like service corridors, roof voids above later ceilings, and modern additions are the paths for new pipework and ductwork.

External equipment placement is one of the biggest constraints. Condenser units cannot sit on a significant facade or be visible from the primary street frontage. Ground-level placement behind the rear building line is the standard approach. In multi-storey heritage buildings, rooftop plant is sometimes acceptable if it sits behind a parapet and cannot be seen from the street. The Heritage Council assesses visual impact from key public viewpoints.

Inside the building, VRF systems solve most problems. Refrigerant pipes are 6 to 16 mm in diameter, compared to rectangular ductwork that can be 300 to 600 mm wide. Pipes can be routed through floor voids, within non-significant wall cavities, or above suspended ceilings in rooms where the original ceiling is not exposed. Where the original ceiling is the significant element, floor-based solutions like underfloor displacement ventilation or console units become necessary.

Performance Solutions are common on heritage projects. For example, a heritage building with fixed single-glazed windows cannot meet the NCC energy efficiency Deemed-to-Satisfy provisions. The engineer prepares a Performance Solution that demonstrates the building meets the intent of the Performance Requirements through a combination of system efficiency, controls, and operational strategies. This requires modelling and a formal report accepted by the building certifier.