When it comes to understanding building energy certificates, I would rather understand one useful detail properly than rush through a long list of ideas. Knowing what a certificate describes can help a reader ask more precise questions about a building. Seen this way, building energy certificates becomes a topic to explore rather than something to sum up too quickly. I would be interested in a simple example, because it is often the ordinary details that make an idea memorable. Which parts of an energy certificate are hardest for a first-time reader to interpret?