Glazed Roof - sealed unit edges

[goldnet]

We had a kitchen extension installed 5 years ago. The roof consists of 4 large (8ft x 2ft) sealed doubled-glazed panels on aluminium glazing bars. When installed, the front edges of the panes (which hang over the gutter) were left unprotected apart from a strip of black 'duct' tape. This has now weathered away and I need to know whether the edges require any form of protection or if the manufacture of the panels is weatherproof. The panes are sealed with a black silicon/rubber material about 1/8" into the pane, before the aluminium internal seal. Someone has mentioned that usually there is an aluminium foil around the edges as well but we see no sign of that. My thought had been to cover the edges with, say, a 1/2 - 1" aluminium right-angle extrusion siliconed to the top surface. Advice welcomed...