The goal of Switzerland's climate policy is to reduce CO2 emissions by limiting annual energy consumption to 1 tCO2. One key area that produces a considerable amount of CO2 emissions is the building sector. Switzerland's goal is for all buildings to operate with zero CO2 emissions by 2060. To reach this goal, there are different ways to assess the energy efficiency and emissions of a building. One method is a diagram that classifies buildings into different classes (A to G, for high to low efficiency), based on the Non-Sustainability Exergy (NSE) diagram. This project plans to propose a new energy class based on an analysis of the residential sector. To create the new class, specific buildings were modelled with possible alterations that could lead to zero-emissions. First, the current energy usage and emissions of the buildings were calculated and they were classified according to the NSE diagram. Using the results, a new energy classification system was defined, along with a tool to help building owners plan renovations using the new system.