Everyone is looking for ways to reduce their heating and cooling bills. When you are designing a new home, one of the simplest ways to make it more energy efficient from the start is to think carefully about which way your windows face.

Window placement is one of the most important decisions in the design of a new home. Get it right and rooms stay warmer in winter and cooler in summer, with far less need for heating and cooling. Get it wrong and some rooms will never feel comfortable, whatever the air-conditioner is set to.

Each direction behaves differently. Sun from the north, east, west and south arrives at different angles and strengths through the day and across the seasons, so a window that works well facing one way can cause problems facing another.

Here is how each orientation performs in Perth’s climate, to help you plan with your designer and window supplier. If you are still choosing land, start with the block itself – read more about choosing a block with the right orientation.

North-facing windows

In the Southern Hemisphere the sun tracks across the northern sky, so north-facing windows receive the most useful sun. They get some sunlight throughout the day without the harsh glare of the low morning and afternoon sun.

North is the ideal orientation for the rooms you use most, such as living and dining areas and the kitchen. In winter, the low sun reaches deep into these rooms to warm them. In summer, when the sun is high, correctly sized eaves or awnings keep it out.

Getting the eave size right matters. As a general guide, an eave that overhangs by about 45% of the height from the window sill to the underside of the eave shades north-facing glass in summer while still letting in the winter sun. Eaves that are too deep can block that winter sun and work against you.

East and west-facing windows

East and west-facing windows take the full force of the morning or afternoon sun. During a hot Perth summer this can quickly overheat a room and create uncomfortable glare. If you do include east or west-facing windows, make sure they have good external shading, such as awnings, external blinds or shutters, or deciduous planting.

South-facing windows

South-facing windows receive no direct sun in winter and only a little early or late in the day in summer. That makes them better for views and ventilation than for warmth.

Because they can lose heat in winter, south-facing windows benefit from low-e glass or double glazing. Opened up in summer, they let in cooling southerly breezes.

Windows in higher-density areas

On a smaller lot or in a higher-density area, neighbouring buildings will shade your home and change how wind reaches it. Here it pays to design for your actual site rather than follow window trends.

If tall buildings surround you, full sun is less of an issue, so east and west-facing windows can work well. Avoid full-height glazing where the lower half will sit in permanent shade and lose heat; raising sill heights reduces that wasted area.

High-level south-facing windows can also act as vents, drawing warm air out of the home to help it cool.

Choosing the right glass

Whatever the orientation, the glass itself makes a big difference. Low-e glass and double glazing both reduce heat loss in winter and heat gain in summer, improving comfort and the overall thermal performance of your home.

Two ratings make it easier to compare windows. The U value measures how much heat passes through the whole window – the lower the number, the better it keeps heat in during winter and out during summer. The solar heat gain coefficient (SHGC) measures how much of the sun’s heat comes through the glass – a lower SHGC keeps rooms cooler, while a higher SHGC can help north-facing rooms capture winter warmth.

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