About two months ago we challenged what we perceive to be a bias in favor of ultra high density, subsidized housing on the part of urban planners who should be engineering cities but often seem to want to engineer society while they’re at it.  These comments culminated (for now) with our Critique of New Urbanism (also known as “Letter from Wingnuttia”) posted back on December 13th, 2007.

Want to plant a big tree? Not so fast…

The original inspiration for our critique was a listserve sponsored by www.treelink.org, where urban foresters swap advice on how to manage and expand urban forests. 

We warned these people who love trees that there is an inevitable conflict between their desire to expand the urban forest and what appeared to be their collective predilection for ultra high density communities.  

You can’t cram 10-20 ”detached single family homes” onto one acre via infill or within new planned communities and expect there to be room for trees - except of course for trees in public parks and on traffic medians, expensively maintained by public employees.  In the urban environment, the private tree on a private lot is an endangered species, and if that sounds hyperbolic, too bad, because it’s true. 

Now another threat to the urban forest is upon us, and the only surprise is that it hasn’t happened sooner.  Unlike high density “infill” mandates, which we believe are destroying beautiful and irreplaceable semi-rural suburbs under false pretences, protecting solar access is a worthy goal.  We have always been enthusiastic about solar power, and the liberating (and libertarian) nature of off-grid, small scale, privately owned energy and water systems.

So when we learned a homeowner in Santa Clara, California, is suing his neighbor because their redwood trees are growing up to shade his rooftop photovoltaic system, there wasn’t an immediate reaction either way.  While we lean towards favoring the trees, we can certainly appreciate the concern somebody might feel if they dump $20,000 into rooftop photovoltaics only to see their yields relentlessly lowered in direct proportion to the height of their neighbor’s redwood trees.  What do you do?

Rhonda Berry, Executive Director of the Silicon Valley based Our City Forest, was quoted in a report on the lawsuit (S.J. Mercury, “Tree Huggers Should Trump Solar Lovers“) as suggesting “we should develop neighborhood solar hubs - at schools or other public buildings - to provide energy to surrounding homes instead of putting panels on every house.”

Berry is on to something, although this conflict is just beginning and her idea is only part of a possible solution set.  But if homeowners invest in solar power systems and reap the payback therein, why should that require them to put the installation on their own roof?  Photovoltaics installed on one residential rooftop still cost about $10 per watt, whereas larger scale systems only cost about $6.00 per watt.  That is a lot of savings to leverage, and property owners in sunny areas away from prime land, or owners of large commercial buildings with huge rooftop areas ought to be able to capitalize on this.

It’s time for virtual power companies to form.  Why should I own a photovoltaic system on my own roof, when I can own a piece of a larger system and make a more cost effective investment - and still enjoy shade from my neighbor’s big urban trees?  Is there a business model here?