How passive ventilation can lower green house emissions
The largest factor contributing to a households emissions is the consumption of power. The Australian Bureau of Statistics (2010) states "In 2007, Australia's residential sector accounted for around 9% of total greenhouse gas emissions, an increase of 25% in emissions since 1990." Additionally heating and cooling methods took up the greatest proportion, 40%. On the market today there are a large variety of ways you can cool a building. The one which produces the least amount of green house emissions is passive ventilation and passive cooling systems.
So, what is passive ventilation? The promotion of air movement using naturally occurring thermal convectional currents. As hot air rises the cooler air is drawn in to replace it. If the hot air can't escape the dwellings temperature dramatically increases. Ceiling fans will only circulate the hot air meanwhile the conventional air conditioner will be working overtime to cool the air. If we add to this equation high level operable windows which allow the hot air to escape whilst drawing in fresh cool air through lower windows, ideal thermal comfort is restored.
In the initial design stages there are several passive ventilation features that should be incorporated: Place several bays of operable windows as high as possible in the dwelling. Using a pitched roof to create a passive airflow path. Correct orientation and position of windows, coupled with uninterrupted airflow pathways. The building itself should be positioned with wind direction in mind which then allows a wind passage to run through the building therefore naturally cooling.
Passive ventilation can be controlled and adjusted to suit a buildings comfort needs. Slimline actuators on high level louvres, awnings or sliding windows can make operation a breeze. Once passive design has been incorporated into the house, there are added bonuses of reduced lighting costs due to additional sources of light through the high level windows. As well as safety options which include smoke detection interface. Recent studies suggest in climates with hot and humid days and cool refreshing nights, a building should incorporate a temperature sensor to purge the cooler air in at certain times throughout the night. This constantly maintains thermal comfort and can avoid the need for mechanical cooling entirely.
In 2004 the Sustainable Home Brisbane located in Seventeen Mile Rocks was constructed to showcase sustainable products and practices. This house utilised many sustainable aspects and features one of which is the passive design to incorporate uninterrupted ventilation. Unique Window Services consulted in the early design stages to achieve optimal passive ventilation, latterly installing slimline actuators to allow operation of the high level windows. (see pictures below)
The core principle of passive ventilation is the key to a more sustainable future and the way we think about heating/cooling systems. If these methods are integrated into new home designs or renovations the energy consumption rate of a residential home and its green house emissions will dramatically decrease.
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