IDA Indoor Climate and Energy is a recently developed tool for building performance modelling and simulation. It represents a new generation of BPM software in several ways. (1) It is entirely imple- mented in a general-purpose simulation environment, IDA. (2) All models are available as NMF source code. (3) It covers a range of advanced phenomena such as integrated airflow and thermal models, CO2 modelling, and vertical temperature gradients. (4) It has a multi-level GUI to accommodate different types of users. An overview of the new tool is given and the paper is concluded with a discussion of CAD integration issues.