The word eco means nature (in Greek oikos means house), so an Ecohouse would be a place that respects the environment (literally, a house inside a house). It would be easy for all of us to be ecologically friendly, in complete simbiosis with nature: we just need to live the way we did 10.000 years ago, hunting, planting, and living in shelters with no water or energy...It would not be wise, since many of us would die from starvation, diseases or disasters. But the way our ancestors lived may help us understand why we need to rethink our relation with nature. Our ancestors fought for their individual survival on a daily basis, and those with technology and resources (virtually unlimited at that time) had a step ahead.Today we fight for the same survival, but based on the benefits that we have today, and some of us are way ahead because of access to technology and resources (clearly limited when faced to the world population today).Before explaining the number of ideas gathered in this work, its necessary to understand Sustainability and the concepts and principles that inspired this work.Sustainability is the ability to live respecting three factors:- environmental (good for the planet and its resources);- social (good for other people, be they near or far);- economical (accessible to everyone to purchase and maintain).Therefore, the ideas described are aimed to those with few natural resources, social problems and financial restrictions. If you are not in one of these categories, you can use them easily, or even improve them, according to your needs. Anything you save from nature will be good to others.