Since the 1990s the push to reduce energy use in buildings has been escalating, driven latterly by the increasingly pressing global need to reduce levels of the greenhouse gas emissions from building that are so devastating to our climate. But the hasty adoption of new ways of doing things can often mean mistakes are made simply because of a lack of hands-on experience with the emerging systems being promoted. The viewing of ‘innovation’ as a good thing in the quest for better building can sometimes have unintended consequences, some of which can leave architects wide open to litigation. One of the most contentious areas amongst many involved in the building industry is the trend towards increasingly ‘Airtight Buildings’, often reinforced by emerging Building Regulations. In this article we address some of those ‘Airtight’ concerns and proffer advice on the subject gleaned from recent research, much of which was assimilated and undertaken for a doctoral thesis by Grainne McGill at Queen’s University, Belfast. What architects need is sufficient confidence in their ‘water-tight’ reasons for making related design detail decisions that even if they do fail they will have been deemed to have acted with due care and diligence and not held responsible for subsequent construction failures. We hope the following article will help them understand the issues involved, and point the way to reasonable and professionally competent solutions that will boost that confidence in the rapidly changing building markets of today.