1 INTRODUCTION Window components are susceptible to water entry over their expected life [Lacasse et al. 2007] hence there is a need to ensure the window installation de- tails permit adequate drainage at the rough opening of the window subsill. However, providing proper drainage may also affect air leakage through the as- sembly and under cold weather conditions condensa- tion may form along the window at the sill or along the window sash and glazing panels. Do window in- stallation details that incorporate sill pans increase the risk for condensation on the window components in which air leakage paths may be prominent at the sill or elsewhere in the window assembly? There exist several standard laboratory test meth- ods for determining the potential for the formation of condensation on windows, however the essential as- pects of such methods were first proposed by Sasaki [Sasaki, 1971] and the standardisation work carried out in AAMA [AAMA, 1972; AAMA, 1998], ASTM [ASTM, 2000] and CSA [CSA, 2004] follows on these initial efforts. These standards prescribe the overall test protocol, temperatures of the room side and cold side, and maximum relative humidity under test conditions. A useful overview of these methods is given by Elmahdy [1990]. The essential elements of the method, briefly de- scribed, consist of testing a window in a hotbox chamber, measuring the lowest window glazing and frame surface temperatures from specified locations on the window, and calculating the average exterior air temperature and the average interior air and wall surface temperatures. The “Temperature Index” ( I ) of the window can then be determined based on the following relationship provided in the CSA A440.2 Standard [CSA, 2004]: I = (T s –T o ) / (T i – To) x 100 (1) where T i and T o are the indoor and outdoor air tem- peratures, and T s is the average room-side surface temperature measured in the test. The temperature in- dex is non-dimensional, and represents the interior surface temperature relative to the interior and exte- rior air temperatures. Window-Wall Interface Details to Evaluate the Risk of Condensation on Box Windows W. Maref, M. Armstrong, M.A. Lacasse, H. Elmahdy, R. Glazer National Research Council Canada, Institute for Research in Construction, Ottawa, ON, Canada N. Van Den Bossche Ghent University, Department of Architecture and Urban Planning, Ghent, Belgium ABSTRACT: The development of alternative details to manage water intrusion at the window-wall interface has produced a number of novel approaches to detailing the interface between the window and adjacent wall assembly. Many of these approaches advocate the need to provide drainage at the rough opening of the win- dow subsill given that the window components themselves are susceptible to water entry over their expected life. Depending on the types of windows used and the cladding into which the windows are installed, there arise different methods to provide drainage that may also affect air leakage through the assembly. This in turn may give rise to the formation of condensation along the window at the sill or along the window sash and glazing panels. Hence there is a need to determine if, under cold weather conditions, specific interface details that incorporate sill pans provide potential for condensation on the window components in which air leakage paths may be prominent at the sill or elsewhere on the window assembly. The paper reports on a laboratory evaluation of conditions suitable for the formation of condensation at the window frame perimeter of the in- terface assembly as a function of both temperature differential and pressure difference across the test assem- bly. A summary of the laboratory test protocol is provided that includes a description of the test set-up and apparatus, fabrication details of the specimen and information on instrumentation and calibration and experi- mental results for one type of window (box window).