The best direction for a house to face

In a cool climate in the northern hemisphere, the best direction is the one that puts your main living rooms and biggest windows on the south side. In a hot climate, the bigger worry is the west: low afternoon sun that's hard to shade and heats the house at the worst time of day.

Avenue G, Hyde Park, Austin, at 6 pm on 21 June. Free, no sign-up.

First, which "facing" matters

The direction a house "faces" usually means the front door side. For light and heat, the front door matters much less than where the rooms you use most sit, and where the glass is. A north-facing front with a glazed south-facing kitchen at the back can be a very sunny house. So read this as advice about rooms and windows, not just the front elevation.

Cool climates: face the sun

Where heating is the main cost, as in the UK, Ireland, northern Europe and much of the northern US, the long-standing passive design advice is to put living areas and most of the windows on the south side, keep north-facing glass modest, and use the north side for bedrooms, bathrooms and storage. The US Department of Energy's passive solar design guide (PDF) suggests windows within 30° of true south, kept clear of shade from 9 am to 3 pm in winter.

The geometry explains why. In London the sun at midday is only 15° high on 21 December but 62° high on 21 June. Low winter sun comes straight through south-facing windows and reaches well into the room. High summer sun is easy to keep out with a roof overhang, a brise-soleil or a deep window reveal. A south-facing wall gets both, which is hard to say of any other direction.

Hot climates: keep the west in check

Where cooling is the main cost, the afternoon is the problem. By late afternoon the air is at its hottest, and the sun is low in the west, so it shines almost straight into west-facing windows where an overhang can't reach it. Here's Austin, Texas on 21 June, worked out with the same formulas the sun path map uses:

At noon the sun is nearly overhead, so a south wall barely sees it and a small overhang shades the windows completely. From 5 pm onwards it hangs low in the west-north-west and shines into west-facing rooms for hours. The DOE guide's advice for warmer climates is generously shaded south windows plus north-facing windows for daylight. Common practice is to keep west glazing small, shade it from the outside, or put garages, utility rooms and stairs on that side.

Mixed climates

Many places need both heating and cooling. The usual compromise is the same as for cool climates, south-facing living areas with overhangs sized to block the high summer sun, plus extra care on the west. East sun is less of a worry, as it arrives in the cool of the morning, although bedrooms on that side will get early light in summer.

Southern hemisphere: swap north and south

In Australia, New Zealand and southern Africa the sun is in the northern sky, so living areas should face north. The Australian Government's YourHome guide to orientation recommends north-facing living areas in most climates, with less east and west exposure to avoid summer overheating. In warm, humid tropical areas it puts more weight on shade and catching breezes than on winter sun.

When you can't choose the direction

Most people buy an existing house, or build on a plot where the street decides the orientation. You can still work with it: choose which rooms go where, add shading on the west, plant deciduous trees that give summer shade and let winter sun through, and check what the neighbours' buildings do to your light. Search the address in Sundial, try 21 June and 21 December, and switch to Sun hours to see how many hours of direct sun each side of the plot gets.