Abstract: There has been a long-standing academic interest in experimentation with policy-designs. Researchers such as Charles Sabel and Jonathan Zeitlin claim that such experimentation may help to understand how significant legal, social or economic barriers can be overcome. This appears to be particularly true in the field of environmental policy. This article explores the nature and outcome of this experimentation by evaluating 21 policy-designs that have been experimented with by governments, businesses and citizens in the building sectors in Australia and the Netherlands. Building on the existing literature, it addresses expectations related to policy learning, collaboration, policy-outcomes and experimental biases. The article finds limited support for many of the claims made for experimentation in the current and past literatures. This may be a result of a mismatch between real-world experimentation with policy-designs and how academics conceptualize this process.