Fifth Avenue Passive House

Fifth Avenue Passive House by Zen Architects and Aphi Projects seamlessly mediates between architecture, context, and environment to cultivate a residence in sync with its coastal surrounds. 

Shaped by clients with both passive and architectural intentions, the residence has emerged as a reconciliation of both which has shaped a place that is profoundly contextual, integrated gently into the native bushland landscape of Victoria’s Surf Coast.

The house combines functionality, aesthetics, and sustainability to demonstrate the importance of builder/architect collaboration in realising homes deeply in tune with all the rituals of living unique to inhabitants, homes that rest lightly upon the ecosystems they rest within and those able to intuitively balance striking aesthetics alongside a sensitivity to their built and natural surroundings.

In this joint interview, Clémence Carayol of Architecture & Design speaks with Ric Zen, Founding Director of Zen Architects, and Dale Roberts, Director of Aphi Projects. Together, they delve into the origins of the project and explore how Passive House standards were seamlessly integrated from conception to completion.

Architecture & Design: How did the Passive House standards influence your approach to natural lighting and ventilation in the design?

Ric Zen: The site descends over 10 metres from the road to the rear, opening up to stunning views through established Manna and Messmate gums to the south-east. The street-facing side of the home points north-west, far from ideal for passive solar design.

Passive House standards gave us the freedom to position the house, rooms, and windows to make the most of the views, rather than being confined to perfect solar orientation. Much of our work centres around refined passive solar principles, typically involving carefully modulated northern light. However, that approach would have required compromising client privacy, ease of access, the views, and the preservation of significant vegetation, all of which were unacceptable. 

Embracing Passive House standards allowed us to take a more flexible, user-centred approach to siting and glazing. The result is a home that sits lightly on the land, is accessible despite the steep slope, has a smaller footprint, and enabled us to retain more trees and enhance the site's biodiversity. Each of these outcomes might seem modest in isolation, but together they deliver a highly rewarding experience for the clients.

Our aim was to maintain our design ethos of openness to the outdoors. Ventilation throughout the house exceeds standard requirements, particularly in the living areas, where expansive sliding doors open onto a balcony. This challenges the common misconception that Passive Houses must rely on small operable windows to remain efficient. We invested significant time in testing the right balance of glazing and openings to maximise the benefits for the clients without compromising energy performance.

What specific design strategies did you employ to harmonise the house with its coastal bushland setting while adhering to the BAL 29 bushfire rating?

RZ: The home was designed with deep respect for the land, with an emphasis on protecting existing trees and the site’s biodiversity.
From the street, the modest façade, set well below street level, appears as a single storey beneath the eucalyptus canopy. Its open and welcoming proportions invite interaction with the street and neighbours, enhanced by the glass-roofed front deck with pivoting batten screens. 

This space flows into the front garden, with paving, outdoor seating, and a BBQ area in full view. The open carport also serves as a verandah, offering striking bush and ocean views back towards the street, allowing the landscape to lead the experience rather than the architecture.

We carefully positioned the house, driveway, and carport to preserve as many significant trees as possible. The upper level rests directly on the ground at the upper end of the site. Natural, untreated timber battens, used both externally and internally, help the home blend into the bush setting and weather gracefully over time. The battens are Class 1 hardwoods, durable and compliant with BAL 29 bushfire regulations.

Could you elaborate on the choice of materials, such as recycled ironbark and turpentine, and how they contribute to the home's sustainability and aesthetic?

RZ: Externally, the house features reclaimed Turpentine and Ironbark sourced from Sydney Harbour. The clients were committed to selecting the most sustainable materials available, those that were durable, functional, low maintenance, and visually striking. We shared their vision of a home that directly engages with its natural surroundings, both inside and out, and recycled timber provided the perfect solution.

Inside, we used battens of coppiced regrowth Sugar Gum from the nearby Western Districts, set against black form ply, mirroring the exterior cladding to strengthen the indoor-outdoor connection. Ceilings are made from structural black form ply, while the window frames are black aluminium. This palette subtly draws the eye outward during the day, further enhancing the sense of immersion in nature.

In designing for ageing in place, what considerations were made to ensure long-term accessibility and comfort for the residents?

RZ: With people spending more time indoors than ever, creating a healthy interior environment was a key priority. We selected internal materials with zero or low VOCs, some entirely unfinished, to ensure the highest indoor air quality. 

The HVAC system provides each room with fresh, filtered air. Throughout the house, cork flooring offers a soft, comfortable surface underfoot, is easy to maintain, and adds a layer of insulation to boost energy performance. The home maintains remarkably stable temperatures year-round, and we’re delighted with the comfort and overall wellbeing it provides for its residents.

The house also connects to the street, offering opportunities for the owners to engage with neighbours and passers-by, fostering a sense of community that’s often missing in newer developments.

How did the collaboration with Aphi Projects impact the architectural process and the realisation of the Passive House principles?

RZ: We first connected with Aphi several years before this project, and quickly discovered how closely aligned our values and approach to architecture were. 

Our skills complemented one another naturally. When the clients approached Aphi, they expressed a desire for architecture that was not only sustainable, but emotionally resonant, highly personalised, and rooted in its site, supported by the rigour and reliability of a certified Passive House build. 

Their brief was clear: architecture without compromise, with Passive House principles seamlessly integrated. Aphi recommended us, and from the first meeting, we clicked. The traditional roles of client, architect, and builder were reimagined into a collaborative, respectful partnership, one that all parties embraced from the outset.

Zen Architects worked directly with the clients to design the home and manage town planning, bushfire compliance, and vegetation protection. Aphi handled the technical aspects of Passive House certification, including windows, insulation, membranes, and HVAC systems, and were also responsible for construction.

Their craftsmanship is exceptional, as is their knowledge of Passive House requirements and problem-solving expertise. This home is a true collaboration in every sense.

What were the primary construction challenges in achieving the stringent airtightness and insulation requirements of the Passive House standard from a builder's perspective? 

Dale Roberts: In this project the primary difficulties where, thermal bridge intersection/junctions, particularly where steel was required, (bed wind hanging out of main pavilion, rear balcony suspended over ground floor, box gutter cutting bed and main pavilions in half). 

The full height glass/windows in this project also posed a challenge due to the amount they flexed under pressure, this resulted in greater losses through the windows and consequently having to achieve a much tighter envelope to offset these losses. 

How did you manage the integration of sustainable materials, like recycled hardwoods and cork flooring, into the construction process?

DR: We managed and drove this right from the design phase through construction. We have a close relationship with a small bespoke mill who specialises in FSC and reclaimed Australian Hardwoods and all materials selections where specified well before the project began and in direct consultation with Zen Architects and the owners. 

Can you discuss the installation and performance of the mechanical ventilation system in maintaining indoor air quality and thermal comfort?

DR: In Passive House projects, the installation of mechanical ventilation systems with heat recovery (MVHR) is integral to achieving optimal indoor air quality and thermal comfort. These systems continuously extract stale, humid air from moisture-prone areas such as kitchens and bathrooms, while simultaneously supplying fresh, filtered air to living spaces and bedrooms. 

The core component, a heat exchanger, transfers warmth from the outgoing air to the incoming air, ensuring minimal heat loss. This process maintains a consistent indoor temperature and significantly reduces the need for additional heating, thereby enhancing energy efficiency. MVHR systems are designed to operate quietly and unobtrusively, contributing to a comfortable living environment. 

The performance of these ventilation systems is crucial in maintaining the stringent standards of Passive House design. By providing a constant and controlled air exchange, MVHR systems ensure that indoor air remains fresh and free from pollutants, which is essential for occupant health and comfort. 

What measures were taken during construction to minimise environmental impact, particularly concerning the preservation of existing vegetation?

DR: It was extremely important to Zen Architects and the owners that as much of the natural vegetation (on the existing undeveloped bush site) was respected and retained as possible. Whilst cutting into the site may not seem like the most non-destructive approach, I believe it accommodated more floor space within a smaller footprint, consequently reducing the overall impact on the site. 

The BAL29 classification significantly impacted the amount of vegetation that had to be removed to respect the BMP however, the approach to and interpretation of the BMP was highly considered to ensure only vegetation that absolutely had to be removed was.

The approach connection with site from the street was designed around the existing and very old messmate habitat tree on the Northeast corner of the site and working around and with this tree was critically important throughout construction.

How did your collaboration with Zen Architects influence the construction techniques and outcomes of this project? 

DR: Collaboration with Zen Architects was absolutely critical to the execution of the project and in its ability to be certified as a PH Low Energy Building. This collaboration began long before construction on site. It is important that a project which sets out to achieve PH standard, that it is designed as such from the beginning.

It was a pleasure to work with Architects such as Zen who were so open to a builder’s input on design detailing. This building is a result of the open minded and diplomatic approach to design and construction, which is what enable such a beautiful piece of architecture with Passive House standard performance.

Every detail and specification of the project was considered and collaborated on to ensure Passive House standard and architecture complemented and endorsed each other.