House Orientation: Maximising Passive Solar Design
Your house’s orientation is one of the most impactful decisions you’ll make — and one of the cheapest. A well-oriented home harvests free solar heat in winter and stays shaded in summer. Get it wrong and you’ll be paying for extra heating and cooling for the next 30 years. Here’s how to make passive solar work for you from day one.
Passive Solar Design: The Core Principles
Passive solar is elegantly simple: capture the sun’s energy with no mechanical equipment whatsoever. No panels, no pumps — just intelligent architecture.
The sun sits low in winter (roughly 15–20° elevation at the winter solstice across most of the UK and northern France) and high in summer (around 60–65°). Good orientation exploits that difference:
- In winter: the low sun penetrates deep through south-facing glazing → free heat.
- In summer: the high sun is easily blocked by a roof overhang or external brise-soleil → no overheating.
| Season | Solar elevation (50°N approx.) | Daylight hours | Effect |
|---|---|---|---|
| Winter solstice (21 Dec) | ~15° | ~8 h | Low sun enters deep into the house |
| Equinox (21 Mar / 21 Sep) | ~40° | ~12 h | Moderate gains, natural comfort |
| Summer solstice (21 Jun) | ~62° | ~16 h | High sun, easily blocked |
Tip — The golden rule: 60% of glazing on the south façade, 20% east, 10% west, 10% north. That’s the starting point for any passive solar or bioclimatic design.
Which Room Goes Where?
Placing rooms according to compass orientation isn’t an architectural luxury — it’s basic thermal common sense that pays dividends every single day.
South Façade: Living Spaces
This is your prime façade. Place here:
- Living room / lounge: large glazed doors or windows, maximum solar gain in winter.
- Open-plan kitchen: natural daylight throughout the day.
- Patio / terrace: extending the living space, sheltered by a roof overhang.
South-facing glazing acts as your most efficient “radiator” in winter. A single square metre of south-facing double glazing can deliver 300 to 500 kWh/year of free energy in a temperate climate.
East Façade: Bedrooms
Morning sun is gentle and wakes you naturally:
- Bedrooms: morning light, cool in the afternoon.
- Bathroom: natural light where you need it first thing.
West Façade: Proceed with Caution
Western sun is the most treacherous — low and intense in late summer afternoons:
- Garage, utility room, store: use these as thermal buffer zones to shield living areas.
- Sheltered terrace: if you want to enjoy the sunset, plan a pergola or deciduous trees in front.
Warning — Avoid large west-facing windows. The low summer sun between 5 pm and 9 pm cannot be blocked by a simple roof overhang. The result: a living room that’s a greenhouse in July.
North Façade: Service Spaces
Little or no direct sun — this is your cold façade:
- Garage, utility room, larder: act as a thermal buffer against the prevailing cold.
- Entrance hall, corridor, staircase: transitional spaces that don’t need warmth.
- Home office: consistent, diffuse daylight — ideal for screens.
Keep openings on the north to a minimum. Every north-facing window is a net thermal loss.
Orientation Decision Tree
Summer Shading Strategies
Capturing winter sun is one half of the equation. Blocking summer sun is the other — and it’s non-negotiable. Here are the main strategies, from most to least effective:
1. Roof Overhang (Brise-Soleil)
The number-one solution for south-facing glazing. An overhang of 60 to 80 cm is enough to block the high summer sun while letting the low winter sun flood in.
2. External Adjustable Louvres (BSOs)
Motorised or manual external louvres — highly effective on east and west façades where a roof overhang alone won’t cut it. They can block up to 90% of solar radiation while still admitting daylight.
3. Deciduous Planting
Deciduous trees to the south-west: dense foliage in summer (shade), bare branches in winter (sunlight). A lime or plane tree planted 5 m from the façade acts as a natural air conditioning unit — completely free to run.
Best practice — Layer your shading: roof overhang on the south + external louvres on the west + a deciduous tree to the south-west. That trio delivers summer comfort without air conditioning.
4. External Blinds and Shutters
Less elegant but effective. External blinds block three times more heat than internal ones because they intercept solar radiation before it passes through the glass.
Thermal Mass: The Partner of Passive Solar
Passive solar only works well with adequate thermal mass — the ability of dense, heavy materials to absorb and store heat.
| Material | Thermal mass | Typical use |
|---|---|---|
| Solid concrete | Very high | Ground slab, structural walls |
| Solid brick | High | Internal partition walls |
| Concrete block | Medium | Load-bearing walls |
| Timber | Low | Frame, cladding |
| Plasterboard | Very low | Lightweight partitions |
How It Works
- Daytime: sunlight heats the concrete slab and heavy internal walls.
- Night-time: the materials slowly release the stored heat.
- Result: indoor temperature stays stable, with little or no supplementary heating.
Tip — If you’re building a timber frame (low thermal mass), compensate with a concrete ground slab and internal partitions in brick or dense block. Thermal mass must be inside the insulation envelope — not outside it.
Calculating the Gains
A well-oriented, passively designed house can cut its heating demand by 25 to 40% compared with an identical house facing the wrong way. In practical terms:
| Scenario | Estimated heating demand (120 m², temperate climate) |
|---|---|
| Standard house, poor orientation | 65–80 kWh/m²/year |
| South-facing, no shading strategy | 50–60 kWh/m²/year |
| Full passive solar design | 35–50 kWh/m²/year |
| Passivhaus standard | < 15 kWh/m²/year |
Under Building Regulations Part L (England & Wales) or the equivalent SAP/EPC framework, solar gains directly affect the calculated energy performance. Good orientation makes it easier to meet the standard and can reduce the need for oversized insulation or heating systems.
Common Mistakes to Avoid
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Facing the main façade towards the street regardless of compass direction. The road isn’t a cardinal point — adapt the floorplan, not the orientation.
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Installing large west-facing glazing “to watch the sunset.” Result: a 5°C temperature spike in the living room every July afternoon.
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Ignoring solar obstructions: a neighbouring building, a hillside, or a row of evergreen trees to the south can wipe out every passive solar benefit you’ve designed in.
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Underestimating night-time ventilation: passive solar in summer also means opening windows at night to purge stored heat. Design in openings on opposite façades (north and south) to allow cross-ventilation.
Warning — Before buying your plot, check the orientation and identify any solar obstructions. A seemingly perfect plot that faces north or has tall evergreens on its southern boundary will be a thermal nightmare. Read our article on how to choose a building plot.
Key Takeaways
Passive solar orientation is the highest-return lever in your entire project: zero extra build cost, and heating savings of 25–40% for the full life of the building. Combine south-facing living spaces, summer shading, and adequate thermal mass. That’s the foundation of any sound passive solar or low-energy house design.
Checklist: orientation and passive solar
- Plot orientation identified (compass, OS map or site plan)
- Solar obstructions surveyed (buildings, topography, vegetation)
- Main façade oriented between south-east and south-west
- 60% of glazing on the south façade
- Living rooms south, bedrooms east, service rooms north
- Roof overhang designed for south façade (60–80 cm)
- West shading in place (external louvres, shutters, or planting)
- Internal thermal mass specified (concrete slab, dense block or brick walls)
- Cross-ventilation possible (openings on north and south façades)
- Planning constraints checked (permitted development, local plan)