An experimental study has been conducted on natural convective heat transfer in an idealized double-glazed window with a between-panes louvered blind. A Mach-Zehnder interferometer has been used to obtain full-field temperature visualization, as well as local and average convective heat transfer rates. A blind, consisting of 17 horizontal aluminium slats, was mounted inside a tall vertical enclosure formed by two aluminium plates and two acrylic end spacers. Temperature field visualization and measurements were obtained for three plate spacings and three blind slat angles over a Rayleigh number range (based on the enclosure width) of 4.6 x 10(4) <= Ra <= 1.3 x 10(5). Air was the fill gas. The results show that the inter-pane blind has a strong influence on the local and average convective heat transfer rates. In general, a between-panes blind was found to reduce the average convective heat transfer rate across the window, relative to an empty enclosure. At the three plate spacings studied, a closed blind was found to yield the lowest average convective heat transfer rates.