With the increased demand for retrofits and the simultaneous move towards biogenic, carbon storing materials, the importance for understanding the hygrothermal performance of building assemblies is at an all-time high. Hygrothermal testing has traditionally been undertaken by long-term monitoring of pilot projects or test sample in exposure facilities, but this testing takes a minimum of a year in northern climates. Carleton University’s Centre for Advanced Building Envelope Research has developed a new methodology for conducting detailed hygrothermal testing using their modified guarded hot box and pressurized spray rack, in which detailed hygrothermal data sets can be developed within 6-weeks to 3-months of testing. This paper shows how this methodology has been used across three different projects, including residential and commercial lightweight construction and a heavy masonry wall assembly. The steps taken and a sample of data for each project are shown within the paper, showing that comprehensive hygrothermal testing can be conducted in short periods of time, under laboratory conditions.