This paper analyzes through qualitative and quantitative analysis of European Union (EU) policy documents the framing of EU policy on energy-efficient buildings from the 1970s to 2022. We find that it has been framed in different ways over the decades and the framing has expanded to include more and more benefits. Through this expansion, energy efficiency has been linked to other policy areas, such as security, environmental, economic, and social policy. The shifts in framing can be seen as responses to external events. The expansion can also be explained using two metaphors to analyze how the framing differs depending on political positioning. One where policy is seen as a Swiss knife, able to solve multiple political problems, and one where policy is seen as a Trojan horse, where new policy domains are snuck in by policymakers disguising it as energy efficiency policy to increase EU competency in relation to national governments.