Educate the citizens of the city that own their own older homes to insulate their outside walls and attic with cellulose insulation.
I am exploring insulating my exterior walls with GreenFiber cellulose insulation. This is "green" insulation, since it is made with recycled newsprint. This insulation is blown in through 1" holes in either the exterior of the home, or in the interior walls of the home. A 1" hole saw is used to do the holes between wall joists. A small home, with 915 of square foot wall area, would take about 15 bags of this insulation, for a cost of 148.12. Home Depot rents the blower for free with a purchase of 20 bags. Only problem is the holes needed to be drilled, and later patched. Some effort for a greater reward for years to come. As a DIY project with friends, at this cost a quick return on investment is certain.
While the machine is there, also consider attic insulation as well. 15 inch initial (13.5 settled) coverage will give you a R-value of around 51, which is midrange of the recommended R-value for attics.
All this will cut greenhouse gases by recycling the paper used for the cellulose, and cuts heating and cooling generated greenhouse gases.