Ask HN: Sources of info on retrofitting passive solar?

With heat waves thriving and etc., people could use cost effective, quick solutions to keep their homes comfortable year round and utility bills down. Passive solar design generally keeps buildings more comfortable than things like AC or forced air heat while fostering lower utility bills, but it works best if it's part of the initial design of the building.

It's hard to add passive solar solutions after the fact. However, some things can be added after the fact, such as planting shade trees or painting the roof white.

So before I run off and try to reinvent the wheel, I thought I would ask around. Do you know of any existing sources with good info about adding passive solar solutions to existing development?