This paper presents a relatively new, simple and robust, method for air leakage testing. A thirteen-story multi-unit residential building was tested for air leakage before and after an enclosure retrofit. The building suites had a pre-retrofit NLA(50) average of 6.77 cm(2)/m(2) and an average post-retrofit NLA(50) of 2.82 cm(2)/m(2)-a 58% betterment. The effect of the retrofit on air leakage. rates was assessed and compared to other multi-unit residential buildings across Canada and USA. The case study building was significantly tighter than other multi-unit residential buildings included in published studies. Recommendations were made for field-testing procedures in order to maximize the potential for accurate measured flow characteristics. Field-testing for air-tightness needs to be standardized in order for useful comparative results to be generated in order to inform future research and operational considerations for the multi-unit residential building stock across North America. (C) 2014 Elsevier B.V. All rights reserved.