This article shows you how important the orientation of your building is to its overall energy efficiency and the steps you can take to get maximum benefit.
A correctly orientated building can save a lot of money in no longer required heating and cooling costs expenditure - in effect the building itself maintains a comfortable environment for you with little additional costs. This is especially relevant with rising fuels bills and the increasing costs of electricity. By simply building this way, a house can reduce its heating and cooling costs by 85%!
An extra benefit is that there is nothing as such to break down or fail, hence it being called 'Passive Solar', so nearly zero maintenance costs to incur during the lifetime of the building.
BTW Passive Solar design is nothing new, people having been doing it for thousands of years in numerous cultures, we have just given it a fancy name of late. In fact one of earliest references to Passive Solar principals was by Socrates some 2,300 years ago...
“Now in houses with a south aspect, the sun’s rays penetrate into the porticos in winter, but in the summer the path of the sun is right over our heads and above the roof, so that there is shade. If, then, this is the best arrangement, we should build the south side loftier to get the winter sun and the north side lower to keep out the winter winds.”
So the ancient Greek's knew the power of Passive Solar.
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. Please refer to the diagram below for an explanation.
The 'trick' with Passive Solar is in Summer to use shade to block the Sun heating up the interior of the property, but do so that is just enough to to stop it; then when the Sun goes lower in the Winter that shade is no longer enough to prevent the Sun coming into the property and you get free heat just when you need it.
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. Also by putting your most used rooms on one side of the house means you can effectively 'close off' the part of the house you do not use, again avoiding heating/cooling & lighting costs. It also means that the rooms you use most receive the most natural light, thereby also reducing your lighting costs.
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.
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.
How big the windows should be 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):