How big can a dwelling be and still be green?

Just thinking about some issues to do with improvements to the energy efficiency parts of the Building Code of Australia in terms of the recent ABC TV series “The World’s Greenest Homes”. The one common thread running through the program was the sheer size of the houses – very much demonstrative of thinking that going green meant you can build as big as you like. It seems that this misses the point completely: a reductionist approach to technology without thinking through the process as compared to a whole systems perspective, that is, really thinking through your impacts.nHowever, it was clear that most of the Australian houses shown were much smaller than the North American examples. It was clear that the American green houses were excessive in just about every way. If this is a model for housing the world sustainably, then we are on a seriously wrong path!nIt seems to me that any house to be seriously labelled “green”, we should also look at footprint efficiencies in use of space. We need a debate about how big a house or dwelling can be and still be “green”.nWith the BCA looking at a 6 star standard, this will be really important. As very small footprint dwellings are heavily penalised under the star rating system, it will be the case that smaller, lightweight, low embodied energy buildings with a higher surface to volume ratio will have difficulty meeting 6 stars, when huge, heavy buildings over 400m2 may readily achieve it.nNote that such large buildings have a much greater embodied energy. There are, as yet, no penalties in the BCA for such profligate energy use.nFurther, the rating system does not project the total expected energy usage for thermal comfort: a 150m2 house capable of comfortably accommodating a family of 4, using 80MJ/m2 per annum, uses significantly less energy than, say a 250m2 house for the same size family with a better star rating at 60MJ/m2 per annum.nSo, when talking of the “greenness” of a house, we should take into account the embodied energy and the total floor area of the building, in addition to the total energy per m2 per annum.

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