What is the maximum U-value for fenestration?

The maximum U-value for fenestration refers to the measure of thermal transmittance through a building's windows and doors. It is crucial in understanding how much heat is lost or gained through these openings. A lower U-value indicates better insulation properties, meaning less heat transfer and improved energy efficiency.

In this context, the correct selection indicates a U-value that reflects acceptable energy performance standards as outlined by relevant building codes or energy efficiency guidelines, often specific to certain climates and design conditions. A U-value of 2.2 W/m²·K typically aligns with the standards that allow for a balance between energy efficiency and costs, making it feasible for construction practices to meet the requirements of keeping buildings energy-efficient while being reasonable for builders and developers.

Other options represent U-values that might be either too low for certain applications, making them not feasible in typical scenarios, or they might not align with established standards for various building types or local regulations. Thus, the selected U-value of 2.2 W/m²·K is the most appropriate choice given the context of fenestration performance.