Wood – Attractive and thermally efficient, but needs regular maintenance and is prone to decay.
Clad (either vinyl or aluminum) – Most of the advantages of wood, but with lower maintenance. Color choices are more limited.
Extruded vinyl – Low cost, low maintenance, and nearly as energy efficient as wood. Large windows may bow or warp in hot weather.
Extruded Aluminum – Durable and low maintenance, but will transfer heat and cold without an effective thermal break.
Fiberglass – Stronger than vinyl, thermally efficient. Must be painted on both the interior and exterior.