[permaculture] rural vs urban design
raincascadia at yahoo.com
Sat Aug 29 15:26:51 EDT 2009
The September/October 2009 edition of Sierra magazine has a very telling pair of images on page 21 that shows greenhouse gas emissions per acre versus emissions per household for the Phoenix, Arizona area. The first image shows the highest density of emissions in the urban cores, as you'd expect. However, the second image shows the highest levels of emissions coming from the rural areas. The fact is, with current consumption habits, rural dwellers use way more energy than urban dwellers, an idea that has been floating around a lot lately as folks start looking at their carbon footprints.
However, the kneejerk reaction is to start supporting "smart growth" planning, which emphasizes increased density, in addition to integrated residential/business zoning and good mass transit and bicycle lane systems. I would argue that if we are planning to avoid global warming and to anticipate energy descent, increased density has a limit. In order to have enough space for rainwater catchment, greywater distribution, solar and wind energy harvesting, biomass energy production, food production, and composting within residential areas, I would guess that most buildings cannot be higher than 2 or 3 stories and that there needs to be enough open space around these buildings to grow around 50% of the population's food requirements. This, incidentally, is what older neighborhoods and the much-maligned suburbs used to look like. Higher density structures also have less access to ventilation and contain more thermal mass, resulting in more energy
required for cooling.
Higher density zoning only outcompetes lower density zoning in energy efficiency when it comes to building materials, heating needs, consumption patterns, and transportation, with transportation being the main weak point of lower density designs.
It takes less material to create higher density buildings because of all the shared walls. However, the materials must be of a higher quality, and often more massive, due to the taller designs. This results in a trade-off in energy savings. In smaller and shorter structures, on-site and more basic materials may be utilized to a greater extent, possibly resulting in less embedded energy overall.
As for heating requirements, higher density structures require less heating overall due to the insulating effects of shared walls, floors, and ceilings. However, it is harder to include passive solar design in structures that are deeper than one room north to south, and taller structures block solar access to the buildings next to them.
Consumption patterns are probably more sensitive to culture than the other factors mentioned here, but there is a potential for less consumption of goods in denser areas than in rural areas. The ability to share laundry facilities, food processing equipment, energy technology, farming and landscaping equipment, entertainment, etc., is greater where the population density is highest. However, an individualist culture prevents this to a large extent. Regardless, as prices go up, we should expect more sharing, and designs should encourage this.
Transportation is the Achilles' heal of low density zoning. Since personal transportation accounts for over 40% of the energy currently used by the average person in the US (see www.coolcalifornia.org), it is easy to see how smart growth got its name. However, this will have to change (and already is) as energy prices go up. As an example of what personal behavior and technology improvements can do, my partner and I use 87% less energy for transportation than the average US household of two, and our transportation sector is only 22% of our total. This is true even though we live about six miles out of town and our closest neighbors are half a mile away. We are able to do this through personal restraint and the use of a Prius and electric bicycle. However, I realize that few will be this committed to energy conservation in the near future and this is why I believe that no settlement designs will be successful without a serious consideration
of transportation needs. Siting work areas next to housing and providing abundant opportunities for walking, bicycling, and mass transit are essential for a low energy future. Permaculture homesteads spread out over rural land are definitely not a sustainable design. (Unfortunately, the price of land, current zoning and building rules, and idiotic cultural practices make it very difficult to live a permaculture lifestyle in most urban areas, today.)
All this is to say that sustainable settlement designs are likely to look more like a neighborhood or village than a big city or rural country. City councils and planning departments that focus on increasing density, rather than on encouraging things like local rainwater and energy harvesting and conservation, biomass and food production, and composting are creating communities that will continue to be dependent on vast hinterlands and massive energy inputs. There may be some economies of scale realized in centralized projects outside of the urban zones, but I believe that cities will need to be more self-reliant in the future, as has happened in Cuba. Beyond this, the quality of life is much better where there is open space integrated into the places where we live, and where our needs are being met within the local community.
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