What is the default U-factor for a metal framed, double paned window according to code?

The default U-factor for a metal framed, double paned window is typically set at 0.60, reflecting industry standards and energy codes that assess the thermal performance of windows. The U-factor measures the rate of heat transfer through a window; thus, a lower U-factor indicates better insulating properties.

Metal framed windows generally have higher U-factors due to the thermal conductivity of metal compared to other framing materials like wood or vinyl. This means they are less efficient at insulating against heat loss. Double-paned windows do offer improved thermal performance over single-pane versions, which is why the U-factor does not exceed a certain threshold.

In this case, the choice indicating a U-factor of 0.80 would be inaccurate, as it implies a lower efficiency than what is expected for double-pane windows with metal framing. Understanding these values is crucial for compliance with building codes and ensuring the energy efficiency of a structure.