In this paper natural convection heat transfer in a vented cabinet is investigated. The cabinet consists of a rectangular, partially open, cavity in which a vertical, isothermal plate, simulating an electronic board, is placed. The experiments were conducted by parametrically varying the spacing between the plate and the cabinet walls, and the location and size of the openings. In particular for each cabinet configuration local and average heat transfer coefficients have been determined by means of a non-intrusive experimental technique (schlieren). Measured data, recast in terms of dimensionless numbers (Nusselt and Rayleigh numbers) are presented and discussed. Moreover, visualizations of thermal field inside the cabinet, by means of colour schlieren technique, are provided for a number of geometric and flow conditions.