wood
Window frames made of milled wood, with their thermal performance and maintenance depending on the frame construction.
Wood is one of the most common materials for window frames, and also one of the oldest. It is relatively expensive compared to other common materials, and generally requires the highest maintenance. However if built properly it is a very good insulator, with very low thermal conductivity. It tends to expand with increases in humidity.
The wood forms the frame around the glazing. Its material properties differ from those of the glass and from any exterior cladding over the frame.
Wood provides relatively good thermal resistance, while moisture changes can affect its dimensions. A metal frame has different conductive properties even when the glazing is the same.
