How to improve eco footprint?

Along with that, if you get some eco-upgrade parts (or have a sim with high handiness skill), you can upgrade objects to be energy efficient and have water recycler. Not only will these upgrades decrease power and water usage, it will also contribute towards green eco-footprint.
The other upgrade is fuel cell/H2O siphoner. Unless you farm insects (they give bio-fuel), don't have these upgrades. The main effect is that the object generates its own power/water. If you use bits and pieces to have it generate it, it will contribute towards industrial eco-footprint.

Also avoid outdoor torches that came with Island Living expansion pack. These also contribute towards industrial.

If you want to build in your neighbors' homes, go to manage worlds and click on a house in your sim's neighborhood. There you can enter build mode. If you edit an unowned lot, community lot, or a lot owned by unplayed sims, you'll enter free build mode (no money to worry about).

Edit. Oh, and also make use of lot traits. Equip lots with Eco-Friendly Lot trait so they move towards green faster. Avoit equipping community lots with Landfill Lot trait as they contribute towards industrial.

You have to change up your builds. Pretty well the entire neighborhood since it is an aggregate. Change your wallpapers to the eco ones, same with roofs, get solar panels and what not. Just check furniture for eco score.

Also, do eco N.A.P.s and the new careers. If you max one of the new careers (civil engineer or designer, I forgot the exact name) you can make the item that removes or adds pollution to a neighborhood.

Thanks for the help! :)