Where is conductivity typically higher in a glazing unit, at the edge of the glass or the center?

• A. Center of glass
• B. Edge of glass
• C. None
• D. Both equally

Answer: (B)

Heat tends to flow more readily at the edge of a glazing unit because the spacer and frame create a thermal bridge. Those edge components are typically made of metal or other high-conductivity materials that connect the panes, so heat can bypass most of the insulating air or gas in the center. The center region is insulated by the gas-filled gap between panes, which has very low thermal conductivity, and the glass itself isn’t as conductive as the edge materials. So, the edge of the glass conducts more heat, making conductivity higher there than in the center.