More than one billion people in the world are forced to live in slums and that number is growing rapidly. The inhabitants of these slums are - contrary to what we often think - people with a decent job and a steady income. Nevertheless they can still face major difficulties when it comes to getting a decent house. Rapid urbanization, wastage of resources, expensive building materials, inefficient construction methods and architects who do not share their ideas are all part of the underlying problem. Open Source House has the aim to start a viable social business to provide affordable housing through sustainable design for low income countries. The project started with a design competition in which more than 3100 young architects from 45 different countries participated. The goal of the competition was to design an affordable, flexible and sustainable house. The winning design is currently being realized in Ghana as a pilot case. However, Open Source House emphasizes the value of all entries. Not only the winning design but all of the competition entries are made available on the online Open Source House platform. This offers a wide variety of sustainable designs and continuous open source product development, from which everyone can benefit. This means that people, who urgently need a home, will now have access to a diverse pool of knowledge, creativity, designs and housing.