With electricity and gas bills getting more and more expensive there has never been a better time to use alternative technologies to heat and cool your house.
Using glass to heat an area is definitely not a new technology and if you’ve eaten a tomato in the middle of winter chances are it was grown in a glasshouse.
Passive solar is the name given to the use of the sun to heat up or cool an area without any moving parts .
Let’s start with heating as its the easiest place to begin. I’m going to base all my directions based on the southern hemisphere as that’s where I live if you’re in the northern hemisphere it should be as easy as swapping north to south.
In the southern hemisphere the sun tracks on the northern side of a building and during the height of summer in most of Australia the sun is directly above your house, in winter the sun moves down to approximately halfway between the horizon and the peak height of the summer sun, which is at noon, the sun follows an arc across the sky.
One of the easiest ways to incorporate a passive solar design into your house is to find the north facing side of your house and if possible install as much high efficiency glazing as possible.
If possible the windows should be full height and as big as possible as this will let a lot of sunlight in which as soon as it is in the building is turned into radiant heat and stored in the floor and walls of your house.
Now this is all good in winter but if you miss the next step you could be turning your house into an oven .
The next step to make this a passive solar house is to make sure that the hot summer sun does not come in these new large windows.
One of the simplest ways to do this is an awning the awning should be installed at such an angle that the full winter sun will shine through the windows and into the house and then when summer comes along the awning should shade the full height of the window.
As a rough guide in Perth Western Australia the edge of the awning at the lowest point should be approximately 60 degrees from the bottom or sill of the windows use the horizon as your baseline.
Now using glass to heat a house is easy but how on earth do you use it to cool a house?
To cool a house using the sun you need to know a little bit about how hot air works in a house the first thing that you probably already know is a hot air rises this is what we’re going to use to cool your house.
Some existing house designs are better than others when it comes to retrofitting passive solar technologies and in some cases it may not be possible at all .
The first thing to look for when cooling your house with passive solar is the highest point on the roof on the ceiling line, this is the spot that you should look to vent the hot air that builds up in your house.
Hot air will naturally rise to this spot and if a large enough vent or window is in position air will escape from this point , this presents the opportunity to replace the escaping hot air with new cool air, the reason for this is all about air pressure, the escaping hot air creates a low pressure area that does not want to stay that way as long as there is a sufficient opening with minimal resistance air will be sucked in to equalize the pressure inside the house with the pressure outside.
But where should you put the intake vent or window?
The most simple place to put your intake is on the shady side of your house (in the southern hemisphere this is the southern side), this side of your house will be shaded all day.
You can increase this effect by having a shade house that you pull cool air from or even better if you’re really clever you can use the cooling effect of evaporation to cool the air down.
This is how this works – basically when water evaporates it leaves the area colder than it was so if you wet something and the air blowing on it evaporates the water it will cool it down, think wetting your shirt on a hot day and running in the wind.
This can be as simple as having your intake near a stone waterfall of a pond or you can build an intake box with highly efficient evaporative cooling pads and a recirculating water supply, one of the great advantages of this design is that if the natural air movement is not enough extraction fans can be added.
This has been a very quick intro to a subject that I am very interested in, it is not meant to be a complete ‘how to’ guide just something that might spike your interest in a new topic and take you on an adventure in sustainable technologies.
The elegance and simplicity of these designs is sometimes their downfall as we are a culture obsessed with the new tech gadget fix but if you look at nature for your solutions you will find that it rewards simple elegant solutions.