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> The importance of building orientation

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article imageLast updated 10:42 pm, Tuesday 18th March 2014

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This article shows you how to make use the following facts when orientating your house:

  • The Sun rises in the East and sets in the West, no matter where you are in the world.
  • The Sun is higher in the Summer sky and lower in the Winter sky.

So what does this have to do with correct building orientation and energy efficiency? Answer: Everything, read on.

Using the Sun to your advantage when you orientate your building

The fact the sun is lower in the sky in Winter than in Summer allows us to plan and construct buildings that capture that free heat in Winter and reject the heat in Summer. The orientation of the whole building plays an important part in ensuring such a 'passive' process works. See the diagram below.

building orientation sun path

Ideal house orientation

The ideal house orientation is that the main long axis of the building runs East-West, i.e the ridge line. You can move this by as much as 20 degrees without ill effect, but the most glass on the building must be facing towards the Sun. When deciding the building orientation also take into account the location of landscape features on your plot , i.e. trees and walls, etc which will impact on how you harness the Sun. Ideally you do not want them blocking the sun light as the sun tracks across the sky.

Solar orientation is different to magnetic orientation

It is very important that you remember to orientate your house with respect to the Sun and not to magnetic North (or South), see the diagram below.
Solar North Diagram
Apparent magnetic North can be very different to where Solar North is (up to 20 degrees), this can make all the difference between a passive solar design being viable or not. Your local council should be able to give you details of what the offset should be as this varies from place to place.

Living Area placement

Also of importance is that the rooms most used must be on the side of the house orientated towards the Sun, i.e. the kitchen, lounge, etc. Also put the least used rooms on the side of the house in shade, i.e. garage, laundry; these will also act as additional thermal mass, if properly insulated.

Design your house for the whole year

Since you live in your home through Summer and Winter, you should design it for the entire year. It is important to be comfortable all year long and not just for a single season. Sometimes, solar homes are built with large areas of upward, tilted, south-facing glass, designed to catch every bit of sun, Winter or Summer. While tilted glass does maximize heat gain during the winter months, it also maximizes that same heat gain during the summer. If you understand that the rays of Sun's high Summer arc will bounce off vertical, south-facing glass and reduce heat gain, you can let nature do the work for you in a passively designed home, read this article on how to do it.

More advice and useful links on the next page.

Although do remember glass tilted away from the vertical has much worse insulation qualities as it improves its ability to interact with more new 'airspace' at once (think about the cooling effect and air dropping, being horizontal allows the glass to cool its whole area of new air at once; rather when vertical interacting with a stack of cool to hot air in a room.  Being horizontal reduces insulation qualities by about 50%. This is not silly science, its a known effect, ask anyone who installs skylights for a living.. or check out our online R-Value tool). Therefore you will have to improve the insulation qualities of the glass to offset this effect in Winter.

Energy saved through correct building orientation

It is reckoned that a correctly orientated passive solar building will reduce its energy consumption by 30 to 40 percent. When combined with additional qualities, like the right levels of insulation, this saving can be further boosted. For further advice on passive solar principals see this detailed article.

Solar energy uses

Something not to be forgotten is that a correctly orientated building will usually have a roof line running perfectly East to West. This is ideal for mounting on Solar water heater panels (Solar water heating article) or solar panels for electrical generation (Solar power article).You can also add on solar 'air heaters' or Trombe Walls to further utilize the Sun. You can even create a 'solar greenhouse' to trap solar heat within a conservatory joined to the house.

How big should the windows be?

This all comes down to three things: How 'strong' the sun comes into the room, which side of the house the window is on and the floor covering..

For North facing windows:
If the solar access is good (i.e. nothing blocking the sun as it tracks across the sky) and the floors are concrete slab (or slab with tiles on them):

  1. The area of the North facing windows should be large; somewhere between 10-15% of the building's total floor; and
  2. The area of the North facing windows in each individual room can be up to 25% of the room's floor area.
If the solar access is good and floors are timber:
  1. The area of the North facing windows should be large; this time around 10% of the buildings total floor area, and
  2. The area of North facing windows in each room can be up to 20% of the room's floor area.
If it is the case that solar access is poor (i.e. lots of trees):
  1. The area of the North facing windows be kept small; less than 8% of the total floor area, and
  2. Keep the window area in each room less than 15% of the room's floor area.
For South facing windows:
Keep the South facing windows small:
  1. Total window area should be less than 5% of the total floor area.
  2. Windows in individual rooms less than 15% of the room's floor area.
For East facing windows:
Less than 5% of the total floor area and 15% of the floor area of each room.

For West facing windows:
Less than 3% of the total floor area and less than 10% of the floor area of each room.

Conclusion on building orientation

Correct building orientation is critical to reducing your energy consumption and creating a living space that is naturally comfortable to live in. Also by reducing your energy consumption you are doing a lot to help the environment and live a more sustainable lifestyle. It something that every building should really take into account and utilize.

Recommended Reading

A selection of books we recommend that will help you with using the Sun in your home.
Or visit the Passive Solar category in our Online Store for more books on the subject of Passive Solar.

Related Articles and Links

Related Tags: building orientation, passive solar, sustainable architecture, sustainable design, home, home design, passive design

Related Listings: Insulation, Green Architects

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