During an energy audit, how is the effectiveness of windows evaluated?

The effectiveness of windows during an energy audit is evaluated primarily by measuring their U-value and assessing air leakage. The U-value measures the rate of heat transfer through the window, indicating how well the window insulates against heat loss in the winter and heat gain in the summer. A lower U-value signifies better insulating properties, which contribute to overall energy efficiency in a building.

Evaluating air leakage involves assessing how much air escapes through gaps around the window frames. High levels of air leakage can lead to significant energy loss, thereby reducing the overall efficiency of heating and cooling systems. By measuring both the U-value and air leakage, energy auditors can gain a comprehensive understanding of the windows' performance and their impact on energy consumption in the building.

The other methods mentioned, such as checking color and design or comparing with older models, do not provide useful insights into the energy efficiency or thermal performance of windows. Instead, the focus should be on quantifiable metrics like U-value and air leakage, which directly affect energy loss and comfort within the home.