Super Sustainable House Design in Victoria – A High-Performance, Future-Ready Family Home

Orientation, Super Wall Cladding, Energy Payback & Planning-Ready ESD Explained

Super Sustainable Home Design in Victoria

Client Brief: A Truly Sustainable Duplex for Long-Term Family Living

A client approached us seeking a super sustainable duplex house design for her family that would be comfortable, efficient, and resilient for decades to come. In response, we proposed a double-storey home with four bedrooms, carefully planned zoned living areas, and primary living spaces oriented to the north to maximise passive solar performance.

From the outset, the goal was not just sustainability in name, but a measurable, high-performance outcome that responds directly to Victoria’s climate, planning frameworks, and rising energy costs.

Proposed Build & Design Strategy

Here’s a build strategy + design considerations to get most sustainability benefit:

1. Design & orientation: Start with good passive design — orient living spaces for solar gain in winter, shading in summer; cross‑ventilation; roof overhangs; window placement. This reduces energy demand year‑round.

2. Structure choice: Decide whether to go full natural build (rammed earth / hempcrete / straw‑bale) or hybrid (timber frame + insulated envelope + eco‑finishes). For many suburban builds in Victoria, hybrid may provide best balance of cost, durability and sustainability.

3. Insulation & envelope sealing: Use high‑quality natural insulation (e.g. wool, hemp, Ecowool / Earthwool), airtight membranes, good glazing/windows — to minimise heating/cooling needs.

4. Finishes & materials: Use low‑VOC paints, sustainably‑sourced or recycled timber, recycled steel or materials for roofing/structural elements if needed.

5. Landscape & soils: Before landscaping, amend soils with biochar. Select native/drought‑tolerant plants & trees; design garden for water efficiency (mulch, native groundcovers, rainwater capture).

6. Water & energy systems : Consider rainwater harvesting, greywater reuse, solar roof panels / passive solar heating, energy‑efficient appliances. These help reduce long‑term operational footprint and utility costs.

We researched this subject further, and our findings are below.

1. Starting With Orientation: The Foundation of Sustainability

2. Layout: How a Sustainable Floor Plan Works

3. What Is a Super Wall System?

4. What Material Is Used for External Cladding?

5. Typical Super Wall Build-Up (External & Internal)

6. Flat Roof Design for Sustainable Homes

7. Energy Systems: All-Electric & Net-Zero Ready

8. Cost vs Energy Payback: What Do the Numbers Say?

9. Water, Landscaping & Biochar

10. Typical Construction Cost (High Level Guide Only)

1. Start With Orientation: The Foundation of Sustainability

Orientation is the single most cost-effective sustainability decision.

• Living and family areas face true north

• Bedrooms face east or south

• Garage, laundry, bathrooms form a western thermal buffer

• Roof planes aligned to maximise north-facing solar PV

Good orientation can reduce heating and cooling demand by 30–50% before any mechanical systems are installed.

1. Layout: How a Sustainable Floor Plan Works

For a 240sqm double-storey home:

• Ground floor: open-plan living, kitchen, dining and a flexible study/guest room

• Upper floor: three bedrooms, bathrooms and a secondary living space

• Services stacked vertically to reduce plumbing runs

• Stair void used as a natural stack ventilation chimney

  
  

Compact building forms with shallow floor plates allow:

• Better daylight penetration

• Efficient cross ventilation

• Lower embodied carbon

3. What Is our Super Wall System?

A Super Wall is a high-performance external wall assembly that prioritises:

• Continuous insulation

• Airtightness

• Minimal thermal bridging

• Durability and moisture control

It is not a single product, but a layered system.

4. What Material Is Used for External Cladding?

For a Super Wall – non-fire-rated configuration in Victoria, the external cladding is typically one of the following:

Fibre Cement Panels (Most Common Choice)

• Non-combustible or Deemed-to-Satisfy under NCC for Class 1 dwellings

• Excellent durability and low maintenance

• Compatible with ventilated rainscreen systems

Installed cost: ~$120–$180 / sqm TBC

Timber Cladding (Used Selectively)

• Thermally modified timber or durable hardwood

• Low embodied carbon and strong architectural appeal

Installed cost: ~$180–$300 / sqm TBC

Metal Cladding (Architectural Look)

• Aluminium or steel sheet systems

• Lightweight, recyclable, long life

Installed cost: ~$160–$280 / sqm TBC

Best for: Upper levels or expressed modern forms

5. Typical Super Wall Build-Up (External → Internal)

1. Fibre cement / timber / metal cladding

2. Ventilated cavity (20–40mm)

3. Breather membrane

4. Continuous rigid insulation (mineral wool or PIR)

5. Structural timber or engineered timber framing

6. Bulk cavity insulation

7. Airtight membrane

8. Internal service cavity

9. Plasterboard

   
   

This approach delivers:

• Very high thermal performance

• Long-term moisture management

• Lower operational energy demand

6. Flat Roof Design for Sustainable Homes

Flat roofs must be designed carefully.

Best practice includes:

• Warm roof system (insulation above structure)

• High-performance waterproof membrane

• Concealed drainage with overflow provisions

• PV-ready layout with shading analysis

Flat roofs also support future options like green roofs or roof terraces.

7. Energy Systems: All-Electric & Net-Zero Ready

A modern sustainable home in Victoria should be 100% electric.

Typical specification:

• Reverse-cycle heat pump heating & cooling

• Heat pump hot water (300L+)

• Mechanical ventilation with heat recovery (MVHR)

• 8–12kW solar PV system

• 10–15kWh battery storage

• EV charger provision

This configuration eliminates gas, reduces bills and future-proofs the dwelling.

8. Cost vs Energy Payback: What Do the Numbers Say?

Sample feasibility (Metro Victoria):

• 10kW Solar PV

  • Annual generation: ~14,600 kWh

  • Payback: ~4.6 years

• 10kW PV + 12kWh Battery

  • Higher self-consumption (~70%)

  • Payback: ~7.2 years

9. Water, Landscaping & Biochar

Sustainability doesn’t stop at the building envelope.

Integrated site systems include:

• 15,000–25,000L rainwater tanks

• Toilet, laundry and irrigation reuse

• Permeable paving and rain gardens

• Biochar-amended soils for carbon storage

• Food forest and native habitat planting

Landscaping becomes infrastructure, not decoration.

10. Typical Construction Cost (High Level Guide Only without final drawings)

For a 240sqm high-performance double-storey home:

Item	Estimated Cost
Base construction	$770k – $890k
Super Wall & airtight upgrades	$70k – $110k
High-performance glazing	$55k – $85k
Solar + battery	$25k – $40k
HVAC + MVHR	$30k – $43k
Water systems & landscaping	$42k – $70k

Total: ~$1.0M – $1.25M (excl. land, professional fees & statutory fees)

Example Materials & Products (Sustainable + Low‑Env Impact)

Component / Use	Suggested Material / Product / Supplier Type	Why / Benefits
Structural framing / framing & cladding	Sustainably‑sourced plantation timber, recycled timber, or composite timber/cladding	Timber has low embodied energy, stores carbon, is renewable/recyclable — better than concrete/steel for carbon footprint. Composite timber from recycled content reduces demand for virgin wood and helps divert plastic/waste from landfill.
Flooring / Internal joinery / Non-structural plywood (where needed)	Recycled / sustainably‑certified plywood or boards (avoid high‑VOC MDF/particle‑board) — e.g. a product like Ecoply Non Structural Plywood 2400 x 1200 x 12mm	Using recycled/sustainable plywood aligns with guidelines recommending recycled timber or plantation-sourced timber for lower environmental impact and better indoor air quality.
Wall / External Cladding / Decking / Exterior surfaces	Timber cladding, sustainably sourced wood species (e.g. from plantation pine, thermally-modified pine, or local hardwood where sustainable) or recycled‑content composite cladding	Timber cladding offers low embodied energy, carbon storage, natural aesthetics, and aligns with good practice for Victoria’s climate. Composite cladding can use recycled materials and reduce pressure on forests.
Insulation	Natural insulation materials: e.g. recycled‑glass insulation batts, or more eco options like hemp, cellulose, wool, or recycled polyester insulation	Natural or recycled insulation reduces reliance on fossil‑fuel derived materials, improves indoor air quality, and reduces heating/cooling energy demands.
Walls / Alternative wall materials (thermal mass / passive design)	Rammed earth, earth-based materials, or possibly hempcrete — for portions where thermal mass, insulation, or sustainability is prioritized	Materials like rammed earth have good thermal mass (stabilizing indoor temperatures), low embodied energy compared to concrete, and work well in variable climates like Victoria’s.
Finishes / Paints / Sealants	Low‑VOC paints and finishes (low or no volatile organic compounds)	Helps maintain good indoor air quality, reducing health risks associated with off‑gassing from conventional paints/finishes.

Biochar: What It Is & How It Could Be Used in a Sustainable House / Site

• What is Biochar: It is the charcoal-like, carbon‑rich residue produced by the pyrolysis (heating biomass in low-oxygen conditions) of organic material (wood waste, agricultural residue, etc.).

• Benefits in Soil / Landscape & Gardening: When added to soil, biochar improves nutrient retention, increases soil’s water-holding capacity, reduces nutrient leaching, supports healthy microbial activity, which helps plant growth and reduces the need for synthetic fertilisers.

• Construction / Building Use (Emerging): Biochar has been proposed and in some cases used as an additive or supplement in building materials. For example, when mixed with clay, lime or other matrix (e.g. in plasters or certain composites), biochar can contribute to breathable, moisture‑regulating, thermally efficient, and potentially more sustainable walling or finishing systems.

• Carbon‑Sequestration Potential: Because biochar is stable over long times, adding it to soils (in landscaping around your house or for gardens) can lock carbon away for decades or more — helping offset some of the carbon footprint of the building and contributing to long-term sustainability.

Tree / Plant Selection for Landscape & Carbon / Biodiversity

A sustainable house design isn’t only about the building materials — landscaping around the house matters too. For a home in Victoria, consider:

• Native eucalypts or local indigenous trees/shrubs (suitable to your region) — they sequester carbon, support local biodiversity, and are adapted to local climate and soils.

• Fruit or food‑producing trees & native shrubs — to support food resilience, biodiversity, and local ecosystem health.

• Drought‑tolerant native understorey plants / grasses — to reduce water demand, support soil health, work well with biochar‑enhanced soils.

• Use biochar in garden soils / tree-planting soil mix to improve soil structure, water retention and long-term soil carbon — especially valuable in clay/sandy or degraded soils common in some Victorian regions.

What to Watch Out For / Design Principles

• Prefer certified or sustainably harvested timber (e.g. certified by Forest Stewardship Council (FSC) or from renewable plantations) rather than old‑growth native forest timber. This helps avoid negative ecological impacts on habitat and biodiversity.

• Avoid or minimise the use of high‑VOC materials (MDF, particleboard, toxic paints) to maintain indoor air quality.

• Combine sustainable materials with smart design: passive solar orientation, cross‑ventilation, good insulation, thermal mass (where appropriate), water‑efficient landscaping — to reduce reliance on heating/cooling and to lower operational energy costs. This is especially relevant for Victoria’s climate which has cold winters and warm summers.

• Use local suppliers where possible — this reduces transport emissions, supports local economy, and often ensures materials more suited to local climate and regulations.

Key Materials & Systems — What to Use & Why

Rammed earth or Natural Earth Walls

• Why: Very low embodied carbon (especially if unstabilized), excellent thermal mass — helps regulate indoor temperature seasonally in variable Victorian climate.

• Estimated cost: Custom rammed‑earth home build cost tends to be high. Some sources put full-build cost about A$4,000–A$4,500 per m² for high‑finish rammed‑earth homes.

Alternative / Hybrid: Engineered Timber (e.g. Cross‑Laminated Timber – CLT) or Timber Frame + Natural Cladding / Recycled Timber

• Why: Timber stores carbon, is renewable (if sustainably harvested), has lower embodied energy than concrete/steel. CLT and engineered timber panels have growing use as sustainable structural systems.

• Timber cost ballpark: Standard softwoods: approx A$700–$1,200 / m³ wholesale; higher-grade hardwoods significantly more.

• Use case: Good for framing, floors, roof structure, internal joinery; with natural or recycled‑timber finishes for cladding or decking.

Insulation & Thermal Envelope

For good energy efficiency in Victorian climate, insulation matters greatly. Consider natural or low‑impact insulation materials over synthetic, high‑VOC materials.

• Ecowool R2.0 Wall Batt — suitable for wall insulation

• Ecowool R2.5 Insulation — higher density/ thermal performance option

• Earthwool Acoustic Insulation Batts — alternative insulation batts (roof, floor, walls)

These are more environmentally friendly than many synthetic insulation alternatives (e.g. high‑VOC foam or fibreboard), and help with thermal regulation, reducing heating/cooling energy demand.

• Estimated cost range (insulation): For natural insulation options like hemp‑based or batts from sustainable feedstock: raw feedstock (e.g. hemp hurd) recent data suggested price near ~A$6–12 / m² depending on R‑value.

• Benefit: Reduced operational energy demand (heating/cooling), better indoor air quality, lower carbon footprint over life of house.

Finishes & Interior Materials

• Use low‑VOC paints and finishes to ensure healthy indoor air quality. This avoids off‑gassing common with conventional paints/finishes.

• For flooring, cabinetry or joinery — recycled timber or sustainably‑sourced hardwoods/softwoods (ideally certified) to store carbon and reduce need for new resource extraction. Timber also adds natural aesthetics and warmth.

  
  

- Optional / Eco‑Materials: Hempcrete, Straw‑bale, Cob

If you want to push sustainability further (especially for walls or secondary structures) you might consider:

• Hempcrete — a bio‑composite of hemp hurd + lime + water; breathable, insulating, lower embodied carbon than many conventional materials, and with relatively low environmental impact.

• Straw‑bale or natural‑earth‑based walling (e.g. cob, mud‑brick) — these offer carbon‑sequestration, compostable/low‑impact end‑of‑life, and good insulation or thermal mass depending on the mix.

Summary — What This Plan Gives You

• A home with low embodied carbon materials (timber, natural/inert earth-based materials) — better than conventional concrete/brick/steel builds.

• Efficient thermal performance via good insulation + passive design — lower energy demand for heating/cooling in Victorian climate.

• A resilient, long-lasting structure — especially if using earth‑based or timber-based sustainable builds.

• A landscape that captures carbon, supports biodiversity, reduces water demand, and improves soil health (biochar, native plants).

• Over time, reduced operational environmental footprint and likely lower energy/water bills. Also potential carbon‑sequestration through biochar + trees/vegetation.

Construction Cost Breakdown

All indicative costs are based on current Melbourne metro construction rates and are provided for early-stage feasibility guidance only. Final costs are subject to detailed design, council approvals, and market conditions.

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