Lock orientation, living-room aspect, glazing ratios by façade, external shading, thermal mass, cross-ventilation and insulation continuity before NatHERS modelling and BASIX thermal commitments. In NSW, late glass cuts and plan reworks usually stem from design decisions made after the certificate path is already constrained — not from the BASIX tool itself. giantA sequences passive design first so certification risk falls, not rises.
Primary sources: BASIX (NSW Planning Portal); Increase to BASIX Standards; Thermal Performance help; YourHome — Passive design. Confirm live Portal guidance for your project. Last checked September 2026.
Why should passive design be locked before BASIX and NatHERS?
BASIX assesses water, energy and thermal performance for new homes, renovations of $50,000 or more, and pools/spas of more than 40,000 litres (Planning Portal — BASIX). Thermal performance examines design and materials that reduce artificial heating and cooling. Higher thermal and energy standards took effect on 1 October 2023, with thermal outcomes generally aligned to 7 NatHERS stars for most new detached and attached houses (Increase to BASIX Standards).
NatHERS modelling and the BASIX thermal methods (DIY, Simulation, or Passive House standard method) only score what the plans already encode. If living rooms face west, west glazing is oversized, eaves are undersized, or slabs are insulated from winter sun, the model cannot invent comfort — it can only quantify failure. Redesigning glass packages or room layout after a failed run wastes fees, time and client goodwill.
At giantA Pty Ltd we treat passive design as a pre-certification gate: site and floor-plan decisions that YourHome calls climate-responsive — orientation, glazing, shading, thermal mass, insulation and ventilation — are locked before we brief an assessor or enter thermal commitments.
What BASIX thermal methods exist — and what do they assume about design?
The Portal’s thermal performance section offers three pathways (Thermal Performance):
| Method | Who uses it | What it does | Design implication |
|---|---|---|---|
| DIY | Single dwellings with common construction | Estimates heating/cooling loads from inputs (glazing, shading, insulation commitments) | Orientation and glass area must already be sensible; DIY eligibility has floor-area, storey and glazing-ratio limits — confirm on the Portal |
| Simulation | Complex designs, multi-dwellings, broader material range | Accredited NatHERS assessor calculates loads in approved software | Most flexible for custom homes — still cannot fix a poorly oriented plan without redesign |
| Passive House standard | Single dwellings designed to Passive House | Certified Passive House Designer uses PHPP | Highest fabric discipline; not a shortcut around orientation |
DIY and Simulation are broadly equivalent across many dwellings, but outcomes differ because DIY estimates loads while Simulation calculates them. Neither method replaces early passive design.
Related reading: BASIX Simulation for NSW Alterations 2026 · Home Energy Rating / NatHERS Assessment.
How does orientation cut BASIX certification risk?
YourHome states that orientation places the home to take advantage of sun and prevailing winds, and that good orientation can significantly improve comfort and reduce heating and cooling needs (Orientation). For most Australian climates, daytime living areas should face true north (within about 15° west to 20° east of solar north for strong passive heating performance — see YourHome passive heating guidance).
Practical NSW building-design rules we lock early:
- Living, dining and kitchen on the north side where the site allows.
- Bedrooms and secondary spaces on east or south where solar gain is less critical.
- Minimise west living glazing — afternoon sun drives cooling loads that NatHERS and BASIX heating/cooling caps punish.
- Document solar north on site analysis and early plans (not only street north).
On narrow east–west lots, we still prioritise north glass to living rooms and use plan depth, courtyards or borrowed light rather than “solving” comfort with oversized west walls of glass.
What glazing ratios by façade should you lock before modelling?
YourHome notes that glazed windows and doors have a major effect on thermal performance — up to 40% of heating energy can be lost and up to 87% gained through glazing (Glazing). Exact U-values, SHGC and NatHERS climate-zone caps vary by project — confirm heating and cooling caps on the Planning Portal / Energy standards and thermal loads calculator for your address rather than copying another suburb’s numbers.
Design sequencing (before assessor brief):
| Façade | Preferred glass strategy | Risk if locked late |
|---|---|---|
| North | Generous living glass with fixed horizontal shading sized for summer exclusion / winter admission | Undersized eaves → summer overheating → cooling-cap fail |
| East | Modest openings; morning sun; adjustable external shade where needed | Large unshaded east glass → spring/summer cooling spikes |
| West | Minimise; high-performance glass + adjustable external vertical shade if unavoidable | Classic late redesign: glass cut after failed NatHERS |
| South | Daylight without winter solar gain; watch heat loss in cooler zones | Oversized south glass → heating-cap pressure |
For DIY method users, the Portal also sets eligibility limits (for example conditioned floor area, storeys, and glazing as a percentage of conditioned floor area). If your design sits outside DIY criteria, plan for Simulation early — do not discover this after joinery and window schedules are frozen.
How should external shading be designed with orientation?
YourHome’s shading guidance matches what we draw on Sydney and NSW residential jobs: north is the simplest to shade with fixed horizontal devices (eaves, awnings); east and west need adjustable vertical shading, deep verandas or similar because low-angle sun is hard to block with eaves alone (Shading).
Lock before BASIX thermal entry:
- Eave / pergola depth on north living glass (shown on elevations and sections).
- External blinds, louvres or screens on west (and often east) as design commitments, not post-certificate options.
- Avoid relying solely on internal blinds for NatHERS/BASIX credit — external shade is the climate-responsive control.
Shading is also where late “glass upgrades only” strategies fail: better IGUs help, but unshaded west glass still dumps heat into the model.
Where should thermal mass sit relative to north glass?
Thermal mass absorbs and stores heat. YourHome emphasises that mass must work with orientation, insulation, glazing and shading — and that glass-to-mass ratios are critical and best checked through modelling (Thermal mass).
Pre-BASIX decisions giantA locks:
- Expose slab or masonry in north living zones that receive winter sun.
- Shade that same mass in summer (eaves + deciduous or designed shade).
- Insulate slab edges where climate and construction detail require continuity.
- Do not bury all mass behind carpet and joinery on the only solar-exposed floor if you expect winter free heat.
Thermal mass without solar access is dead weight; solar access without mass or night purge often becomes an afternoon furnace. Both patterns show up as heating or cooling-cap stress in NatHERS.
How do cross-ventilation and insulation continuity protect the certificate?
Passive cooling and ventilation reduce reliance on air conditioning. YourHome stresses controlled ventilation and airtightness together — fresh air where intended, not leaks (Ventilation and airtightness; Passive cooling).
Design locks:
- Operable openings on opposite or adjacent façades for cross-breezes in living zones.
- Night purge paths over thermal mass where climate allows.
- Insulation continuity at walls, ceilings/roofs and floors — aligned with BASIX DIY insulation commitments or Simulation assumptions (Insulation commitments — DIY).
- Avoid thermal bridges at slabs, balconies and window reveals.
Insulation without shade can create an “oven”; shade without insulation wastes winter heat. Sequence both with orientation.
What process should clients and designers follow before NatHERS?
| Stage | Decision to lock | Owner | Outcome if skipped |
|---|---|---|---|
| 1. Site analysis | Solar north, overshadowing, breeze paths, climate zone | Building designer | Wrong living aspect locked into DA/CDC plans |
| 2. Concept plan | Living on north; west glass minimised | Building designer + client | NatHERS cooling fail → expensive glass cuts |
| 3. Envelope | Eaves/external shade; insulation strategy; mass location | Building designer | DIY fail or Simulation redesign loop |
| 4. Glazing schedule | Façade-by-façade areas, frames, performance targets | Building designer | Late window package change after quotes |
| 5. Pre-model check | Peer review vs YourHome principles + Portal method choice | Building designer | Wrong method (DIY vs Simulation) chosen late |
| 6. NatHERS / BASIX thermal | Accredited assessor or DIY entry | Assessor / applicant | Certificate delayed; DA/CDC documents reissued |
| 7. Energy & water | Appliances, hot water, lighting, rainwater as required | Design team | Energy score struggle after fabric is already weak |
This sequence is how we cut certification risk on custom residential work: the model validates a climate-responsive plan; it does not invent one.
How do the 1 October 2023 standards change the cost of getting orientation wrong?
From 1 October 2023, higher thermal performance standards generally lift detached/attached houses to 7 NatHERS stars with revised heating and cooling caps, and apartments (where the higher standards apply) to an average 7 stars across the building with individual apartment minima — with noted exceptions for climate zones 9, 10 and 11 in north-eastern NSW and apartment buildings up to 5 storeys (Increase to BASIX Standards). A materials index for embodied emissions also applies for new residential buildings, currently as reporting rather than a pass/fail cap.
Tighter caps mean less room to “buy” compliance with a single appliance upgrade if the façade is wrong. Passive design before BASIX is therefore more valuable in 2026, not less — especially when paired with all-electric energy strategies (All-Electric Homes in NSW 2026).
For renovations at or above $50,000, confirm whether the alterations pathway applies (BASIX for Alterations and Additions). Passive upgrades to existing fabric still benefit from the same orientation and shading logic on new glass.
What should you ask your building designer before modelling starts?
Use this checklist in the concept or design development meeting:
- Where is solar north, and which rooms face it?
- What is the proposed glass area by façade, and how is west controlled?
- Are external shades drawn on elevations (not only noted in a schedule)?
- Where is exposed thermal mass relative to north winter sun?
- Are cross-ventilation openings sized and placed for living rooms?
- Will we use DIY, Simulation or Passive House method — and does the design fit DIY eligibility if chosen?
- Have we allowed time for a pre-model design review before the assessor starts?
giantA is a building designer, not a builder: we coordinate documentation, BASIX/NatHERS sequencing and approval pathways so construction can proceed on a certificate that matches the drawings.
FAQ
Does every new NSW home need BASIX?
Yes — the Planning Portal states that if you are building a new home, undertaking renovations of $50,000 or more, or installing a pool or spa of more than 40,000 litres, you will need a BASIX certificate. Always confirm current thresholds on the Portal.
Is 7-star NatHERS required everywhere in NSW?
Higher thermal standards from 1 October 2023 generally require 7 NatHERS stars for most new detached and attached houses, with apartment rules and exceptions for climate zones 9–11 and apartment buildings up to 5 storeys. Confirm the standards that apply to your site on the Increase to BASIX Standards page and in the BASIX tool.
Can better windows alone fix a west-facing living room?
High-performance glazing helps, but YourHome and practice both show that orientation and external shading dominate summer cooling loads. Expect NatHERS/BASIX pressure — and possible redesign — if living rooms rely on large unshaded west glass.
Should I choose DIY or Simulation for a custom Sydney house?
DIY suits many common single dwellings within Portal eligibility limits. Custom, highly glazed or complex forms often need Simulation with an accredited NatHERS assessor. Choose the method after passive design is locked, not before.
What is the Passive House standard method in BASIX?
It is a thermal performance pathway for single dwellings designed and constructed to the Passive House standard, using a Certified Passive House Designer and PHPP. It is distinct from informal “passive design” principles on a conventional home.
When should thermal mass be decided?
At concept stage, with north living layout — so slab finish, joinery and sun paths align. Modelling can refine glass-to-mass ratios; it cannot relocate a slab after the structure is documented.
Do renovations need the same passive design discipline?
Where BASIX applies (typically alterations ≥ $50,000 or large pools/spas), new or altered fabric should still follow climate-responsive glazing and shading. Simulation for alterations is a restricted pathway — see our alterations simulation guide.
Where do I confirm official rules?
Use planningportal.nsw.gov.au/basix and linked help notes. For passive design principles (not NSW legal caps), use yourhome.gov.au/passive-design.
Next step with giantA
If you are planning a new custom home or major alteration in NSW and want orientation, glazing and thermal mass locked before NatHERS and BASIX — not after a failed certificate — talk to giantA Pty Ltd.
giantA Pty Ltd — building design, DA/CC documentation and compliance-aware residential design across NSW. We are building designers, not builders.