Renovations, Retrofits and Energy Efficient homes in Melbourne
The Tricky Path: Renovations, Extensions, and the Pursuit of Passive House Standards
Embarking on a renovation or extension project is often driven by the desire for more space, improved functionality, or a modern aesthetic. For the environmentally conscious homeowner, the aspiration might extend to achieving the rigorous energy efficiency of the Passive House standard. However, while incredibly rewarding, retrofitting existing structures or seamlessly integrating extensions to meet these demanding criteria presents a unique set of challenges that require careful consideration and innovative solutions. As a leading passive house builder in Melbourne, we've seen these challenges firsthand.
Why is Passive House Tricky for Existing Buildings?
The Passive House standard, renowned for its focus on super-insulation, airtightness, high-performance windows, and mechanical ventilation with heat recovery (MVHR), is inherently easier to achieve in new builds where these principles can be integrated from the initial design stage. Existing buildings, however, come with pre-existing conditions that can complicate the process significantly:
Existing Structure and Form: Older buildings often have complex geometries, thermal bridges in their original construction, and limitations in wall, roof, and floor thicknesses, making continuous insulation challenging. Extensions need to be carefully integrated to avoid creating new thermal bridges at the junction with the existing structure.
Airtightness Woes: Achieving the stringent airtightness targets (a maximum of 0.6 air changes per hour at 50 Pascals pressure for new builds, and a slightly more relaxed but still demanding 1.0 ACH for EnerPHit retrofits) in existing buildings can be a major hurdle. Retrofitting an airtight layer without causing moisture issues within the existing fabric requires meticulous planning and execution. Extensions must also be seamlessly tied into the existing airtightness layer.
Window Integration: Replacing existing windows with high-performance, Passive House certified units is often necessary. However, detailing the interfaces between new, thicker windows and existing walls to maintain airtightness and eliminate thermal bridges can be complex.
Ventilation Challenges: Integrating an MVHR system into an existing building can be disruptive, requiring careful routing of ductwork. Finding suitable locations for the unit and ensuring balanced airflow throughout the existing and new spaces demands thoughtful design.
Unforeseen Conditions: Opening up walls and floors during renovations can reveal unexpected structural issues, dampness, or non-standard construction that further complicate the path to Passive House performance.
Cost and Complexity: Achieving Passive House standards in renovations and extensions often involves higher upfront costs due to specialised materials, increased labour for meticulous detailing, and the need for expert consultation and certification.
The EnerPHit Standard: A Stepping Stone
Recognising the difficulties in bringing all existing buildings up to the full Passive House standard, the Passive House Institute developed the EnerPHit standard. EnerPHit acknowledges the constraints of working with existing structures and offers a more flexible, component-based approach to deep energy retrofits. While still demanding, EnerPHit has slightly relaxed criteria for heating demand and airtightness, focusing on achieving significant energy reductions and improved comfort through the strategic use of certified Passive House components. As a dedicated passive house builder, we frequently utilise the EnerPHit standard for projects aiming for passive house construction in Melbourne.
Strategies for Approaching Passive House Renovations and Extensions
Despite the challenges, achieving Passive House or EnerPHit standards in renovations and extensions is possible with careful planning and the right approach:
Engage Experienced Professionals: Working with passive house architects, designers, and builders who have specific experience with Passive House or EnerPHit projects is crucial. Their expertise in detailing, material selection, and airtightness strategies is invaluable.
Detailed Energy Assessment: A thorough energy audit of the existing building is the first step to identify areas of heat loss, air leakage, and potential for improvement.
Prioritise the Building Envelope: Focus on achieving high levels of continuous insulation and excellent airtightness in both the existing structure and the extension. Pay close attention to junctions and details to minimise thermal bridges. This is key for any passive house construction.
High-Performance Components: Specify Passive House certified windows and doors for both the existing building and the extension.
Integrated MVHR System: Design a well-balanced MVHR system that effectively ventilates both the old and new parts of the building, ensuring good indoor air quality and heat recovery.
Phased Approach (EnerPHit): For more complex retrofits, a phased approach aligned with the EnerPHit Retrofit Plan can be a practical strategy, tackling the most critical energy-saving measures first.
Consider Orientation and Shading: Optimise the orientation of the extension to maximise passive solar gains in winter and minimise overheating in summer. Incorporate effective shading strategies.
Meticulous Execution and Testing: Achieving airtightness requires careful workmanship and rigorous testing (blower door tests) throughout the construction process.
Certification: Pursuing Passive House or EnerPHit certification provides independent verification of the project's performance and ensures that the demanding standards have been met.
The Reward of a High-Performance Home
While the path to achieving Passive House standards in renovations and extensions can be challenging, the rewards are significant. Homeowners can enjoy drastically reduced energy bills, exceptional comfort with stable indoor temperatures and fresh air, improved indoor air quality, and a significantly lower carbon footprint. Furthermore, these high-performance homes often boast increased durability and value.
In conclusion, while not a straightforward endeavour, bringing renovations and extensions up to Passive House or EnerPHit standards is an increasingly viable and crucial step towards a more sustainable built environment. By understanding the challenges, embracing innovative solutions, and working with experienced professionals like a skilled passive house builder in Melbourne, homeowners can transform their existing spaces into comfortable, healthy, and remarkably energy-efficient homes for the future.