Gathering data from site visits and working on old masonry buildings are two of our specialties. That’s why Larkin Architect Limited, Toronto, hired us to help with their refurbishment planning of the historic Metropolitan United Church, a beloved Toronto church built in 1872 and the survivor of a fire in 1928. The church was almost entirely rebuilt after the fire, but nearly one hundred years later, the interior stucco finish in the worship space needed attention. The Metropolitan United Church congregation was interest in lower energy usage and improving occupant comfort, which required adding retrofit insulation to the scope. The BELi team was asked to advise on retrofit options and heat, air, and moisture implications of a thermal insulation addition. We visited the site multiple times: collecting building history information; analyzing utility bills; monitoring indoor conditions, assessing masonry; and conducting a whole building air tightness test. Clear recommendations were drawn for insulation and ventilation retrofits for the buildings.