Pepper Tree Passive House

Description: Pepper Tree Passive House
Building Type: Residential
Location: Unanderra, NSW 2526
Number of Apartments/Units: 1
Treated Floor Area According to PHPP: 60m2
Construction Type: Timber Frame
Year of Construction: 2021

Background

Pepper Tree Passive House is a high performance secondary dwelling designed around an established Pepper Tree. Instead of extensive alterations and additions to the existing home, the new detached building provides the additional amenity required for the young family. As the existing home functioned well for the clients already, preference instead was given to create a new self contained addition and use the budget to create moments of delight across the site. When not being used as a home office by the clients the building is available as a short-stay Airbnb, where those interested in the Passive House standard can experience the higher levels of thermal comfort and air quality afforded by the more rigorous building standards. Pepper Tree Passive House gives the clients a perfect space to work while being able to create a distinct separation between work and home life, without the lengthy commutes and empty building hours experienced in a traditional workplace model. Minimal works to the existing home - including new timber
cladding, repainting the existing concrete tiles lighter to reduce heat gain and the addition of a 12kW building-integrated photovoltaic pergola - allowed the clients to focus on retaining the existing amenity provided by the home and maximise the potential of the site, without crowding it, by creating an infill secondary dwelling that works symbiotically with the home.

Core to the project’s ethos was a need to use both materials and landscaping to capitalise on a strong biophilic connection to the Pepper Tree, as well as regenerate the biodiversity of the site. Despite the small building footprint, it was critical to the project’s success that the site’s natural environment was disturbed as little as possible. The building’s two wings each host an extensive roof garden, filled with a variety of drought tolerant native plants, collecting excess rainwater to be used in the dwelling. The external cladding is charred Shou Sugi Ban allowing the building to blend in, nestled behind the existing street tree line, while removing the need for ongoing maintenance over the material’s lifecycle. Internally, timber products with no-VOC finishes were used throughout, reducing total embodied energy while still providing a well insulated, warm material palette.

The northern wing houses the Living, Office and Kitchen spaces, with a luscious greenery-filled outlook from the breakfast bar, carefully framed a view of mount Keira to strengthen the biophilic connection. Recycled sandstock bricks line the floor and wall area where direct sunlight from the northern highlight windows projects during winter, acting as a thermal battery to the most efficient degree. The narrower and more private southern wing provides the Bedroom, Laundry and Bathroom ensuring the total volume of the building is only as big as it needs to be to protect the Peppertree. Between the two wings sits a floating deck, carefully scribed around the existing Pepper Tree, providing a meditative retreat immersed in the tree canopy. 

The Design/Build Process

The project was first envisioned several years ago by both the client (who is a builder with a Passive House specialty - Souter Built), and Alexander Symes Architect. After the initial concept and design was developed, the client/builder began to salvage and store materials from other projects that would have otherwise gone to waste, for use on this project. This early coordination between architect and client/builder flows throughout the project; from recycled timber and pavers made from waste-concrete, down to screws and fixings left over from other jobs, doing so allowed a massive reduction in new & virgin materials used.

The Brief

While the existing home had a tired and thermally inefficient brick exterior, internally the home’s layout functioned perfectly for the young family. As a response, the project brief developed into one where the existing home had its external envelope upgraded - including new insulation where practical, a ventilated timber screen facade, new skylights, a wrap around deck and solar panel pergola - and a striking secondary dwelling was designed around the 60 year old Pepper Tree in the steeply sloping and under-utilised rear yard. The secondary dwelling was envisioned as a 24-hour space; used as a home office by the family’s growing business during the day, and a short-term stay cabin at night. Designed and built to meet the Passive House standard, the short term stays allow visitors to experience the higher quality of space that the Passive House standard affords, while creating a future proofed studio with western views to Mount Kembla and the treetops outside. Each wing of the secondary dwelling hosts an endemic-planted green roof, allowing the biodiversity of the site to be regenerated despite the extended building footprint created. Minimal works to the existing home - including new timber cladding, repainting the existing concrete tiles lighter to reduce heat gain and the addition of a 12kW building-integrated photovoltaic pergola - allowed the clients to focus on retaining the existing amenity provided by the home and maximise the potential of the site, without crowding it, by creating an infill secondary dwelling that works symbiotically with the home.

The northern wing houses the Living, Office and Kitchen spaces, with a luscious greenery-filled outlook from the breakfast bar, carefully framed a view of mount Kembla to strengthen the biophilic connection. Recycled sandstock bricks line the floor and wall area where direct sunlight from the northern highlight windows projects during winter, acting as a thermal battery to the most efficient degree. The narrower and more private southern wing provides the Bedroom, Laundry and Bathroom ensuring the total volume of the building is only as big as it needs to be to protect the Peppertree. Between the two wings sits a floating deck, carefully scribed around the existing Pepper Tree, providing a meditative retreat immersed in the tree canopy.

Features

Designed and built to the Passive House standard, Pepper Tree Passive House meets the five criteria required for certification:
- Well insulated (R5.4 Walls, R5.0 Floors, R6.5 Ceiling/Roof)
- Airtight construction (2 layers - external vapour-permeable membrane and internal sealed Intello membrane. 0.51ACH final blower-door test)
- High Performance Glazing (Neuffer triple-glazed, timber/aluminium composite framed windows)
- No Thermal Bridges (carefully detailed and constructed timber structure with no thermal bridges between internal and external)
- Heat Recovery Ventilation (Brink Reinvent Excellent 180 Heat Recovery Ventilation unit)
- A Life-Cycle Assessment was conducted that showed despite the higher amount of embodied energy associated with Passive House construction, due to the small, high performance building envelope, low-embodied energy material selection and significant on-site generated & exported renewable energy, the project’s whole-of-life environmental footprint is reduced by 63% compared to a built-as-usual home.
- Fully electric, no gas home.
- Induction Cooktop
- 12kW Solar Panel system, with 14kWh battery
- No paint is used internally to reduce VOCs, and all coatings and materials are 0- VOC and E0 where possible.   

Landscape

Sitting on 18 pad footings across its footprint, Pepper Tree Passive House barely touches the ground, allowing the existing ground plane to remain largely in-tact.

Additionally, the endemic-planted rooftop garden provides additional space for local fauna habitat, while being designed and constructed with falls ensuring adequate
drainage (which is collected and reused elsewhere on site). All external pavers on the site are created from waste concrete, with native groundcover planted between.

Critical to the project is the eponymous 80-year old Pepper Tree, whose health was considered from project outset to ensure it continues to thrive.   

Project Members

Souter Built Pty Ltd provides a range of building services including residential, commercial and heritage restorations. With a passion for building to the highest standard and a creative outlook for problem solving they can deliver a high-end quality product on time and within your budget requirements. They are the builder and client for this project.

Alexander Symes Architect is a registered architect who combines a scientific approach to sustainability with a practical and poetic understanding of crafting a building. Alex has specialist training in the design and delivery of passive houses which we believe offer a pathway towards exceptionally comfortable and healthy homes.