How to Cool my Home Naturally without Air Conditioning – Part 2
In part 1 of “How to Cool my Home Naturally without Air Conditioning” we looked at different ways in which we could cool our home including air conditioning and electronic home ventilation systems.
This article however will look at more environmentally friendly ways that you can cool your home that cost nothing at all to run.
Well clever architectural designs can offer a number of electronic free solutions and one of these is based around the Venturi Effect.
The Venturi Effect is the combination of the Bernoulli Effect and the Continuity Equation. But in case you’re not familiar with either of those things, let me instead explain it using a diagram.
Here we can see an opening at the top of the house, which typically would be some louvers that can be opened and shut as required. The breeze passes through these louvers and then out the other side. The moving air draws in the air below it, in this case out of a particular room in a house. This effect is limited if the rest of the house is closed off, however opening windows, doors or low set louvers will allow fresh cool air to be drawn in from outside as the rising hot air is drawn out and away.
But whilst this system works well on days when there is a breeze blowing, what happens on those days when there is little to no breeze?
Hot air – that is air that has been heated – is less dense than cold air. As a result of this the less dense hot air will always rise above the colder more dense air. This is why hot air rises and is the principle that allows hot air balloons to float above the ground and it is known as thermal buoyancy.
More relevant is the fact that thermal buoyancy is the principle that chimneys are built around. Hot air and rises up the chimney taking the smoke with it. Now if you light a fire in a fireplace and put a lot of green timber on before the coals build up a lot of heat you will probably quickly smoke the house out as the air in the fireplace is not yet hot enough to rise up the chimney quickly. However, when the fire is generating a lot of heat, that hot air rises up the chimney causing a difference in air pressure which causes the air immediately around the fireplace to be drawn in. This is known as a draft and helps keep the fire going by drawing in combustible air. This subtle drawing in of air stops the smoke from escaping into the room as it’s sucked up the chimney and expelled into the cooler denser air outside.
So what do open fires and chimneys have to do with cooling your home? Well actually plenty.
You see the principle of hot air rising and drawing in cooler dense air can aid in creating a draft through your home that can allow the hot air to escape whilst drawing cooler air inside as show in this diagram below:
The effectiveness of this system can be enhanced by creating what is known as a solar chimney. Solar chimneys are constructed of materials that allow for a higher level of heat transmission. In other words they heat the air inside them more quickly. The hotter the air inside the solar chimney the faster it rises, the faster it rises the greater the difference in air pressure the faster cooler air is drawn in through the lower louvers or open windows.
Glass is an effective material for heat transmission, therefore a wall of glass panels on the outside of the physical wall of the home could aid in the rapid heating of the air in the space between the two. Placing exhaust vents in the wall of the home would then result in the air inside the home to be drawn out quickly as the hot air rises in the solar chimney. Open a window on the opposite side of the home and air would circulate through creating comfortable conditions even if no breeze were blowing outside.
So as you can see this system, whilst often enhanced by any sort of a breeze, is not completely dependent on a breeze to be effective. At the very least this type of design can assist in driving the hot air out of your home in much the same way that driving with the windows down in your car sucks the hot air out allowing the air conditioning to be more effective more rapidly.
So if you’re looking for a natural, healthier way to cool your home that works even when the breezes have stopped blowing, talk to a sustainable Architect about the options available for your home. Telephone (07) 3899 9450
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