I am doing an addition and wondering what the greenest insulation solution is. I am thinking recycled material like cellulose but wondering about the chemicals used to process and use on installation.

Anyone know the #1 way to insulate? best build practices?

If you can use SIPs (structurally insulated panels) not only will there be no air gaps in the insulation when they create them the excess material used in production that at a job site would normally make it to a land fill is reused. there are also three factors to consider. The material itself. Is it natural can it be broken down or will it harm the earth long after your home is gone. Two, how well does it insulate, will you save both in heating and cooling seasons to create less energy transfer from inside you home to outside through the use of burning fossil fuels. And three, will it have any effect on the health of your family while you are in the home. For example will it get moldy or will it off gas.
For a remodel it may not be an option but in new homes, the earth is one of the best places to build. into a hill or actually under ground. Think of our ancestors they lived at one with the environment in caves. They maintain a relatively constant temperature and are easier to to heat and cool as there is not much air transfer. The university of Illinois has a whole library underground. Plus think of the extra yard space you will gain. to plant trees.