That's some great info Dr. Ging. By my estimate, you're saying a residential solar system could be installed for about $15k? I know there are certain states that pick up about half the tab either through rebates or tax credits, but PA doesn't yet as far as I know.

How much of a rebate/credit(as a percentage) do you think a Philadelphian could get from local/state/federal departments towards installing a system? And what would the scenario be under whatever legislation Rendell is pushing?

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"Power does what it wants." - George Carlin

Clean by 2016. What is the rush? Why not shoot for 2100?

Vote Republican and we will clean up this dump by 2012.

Perfect, just in time to watch the polar ice caps melt (maybe).

As far as green roofs being walkable, they can be designed as such. However since we are talking about retrofitting buildings to accomodate them, we are much more limited by cost. Certainly we could retrofit almost any existing home to withstand the weight, it is a matter of what is financially do-able. Since this is really all based on the homeowner saving money in some way.

Most of the weight comes from water, actually. Soil itself is very light, but wet soil can be very heavy. Below the soil is layers of different types of impervious or semipervious membranes used to control and direct water runoff, stop plant roots etc, which add weight also.



You are right about the lawn type roof not being used. The idea is to not have to get a mower on your roof. However, you can easily have a garden on your roof which would entail pruning and maintanence.

I have seen rooftop deck structures which channel loads to the supporting party walls of the home. The idea is that you enjoy the garden from the deck, and only acces the garden for maintenance.

Also, I have a 100 year old south philly rowhome which has a roof supporting system which is the same as the floor support system. ie, huge 4" x 8" pine beams spaced at 12"-14". Certainly beefy enough to deal with these loads....I don't think my house is unusual in this respect.

or be just as corrupt as we are now. i honestly don't think there's any real difference between the political parties in this city.

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"Power does what it wants." - George Carlin

The only credit currently available for philadelphia residents as far as I know towards installing solar pv is the federal tax credit for doing so. There was a grant program a few years ago through the SDF, but it expired.

A good place to track this stuff is http://www.dsireusa.org/