Which material has the highest k-factor?

The k-factor, also known as thermal conductivity, measures a material's ability to conduct heat. A higher k-factor indicates that the material is more effective at conducting heat.

Foam glass, which is the chosen answer, is known for having a relatively high k-factor compared to the other materials listed. This is due to its unique structure and composition, which allows it to facilitate greater heat transfer. Foam glass is largely composed of silica, which is a good conductor of heat and contributes to its higher thermal conductivity. This makes foam glass suitable for applications where thermal efficiency is essential.

In contrast, urethane, fiberglass, and polystyrene exhibit lower k-factors as they are designed primarily for insulation purposes. These materials contain air pockets or have structures that minimize heat transfer, making them less effective in conducting heat compared to foam glass. Their lower k-factors make them ideal for insulating applications, as they slow down heat transfer rather than promote it.