What does R-value measure?

R-value measures the insulating effectiveness of materials. It quantifies how well a building material resists heat transfer, with a higher R-value indicating better insulation properties. This measurement is crucial for various applications, including walls, roofs, and floors, as it reflects the material's ability to prevent heat loss in winter and heat gain in summer, thus contributing to overall energy efficiency in buildings.

In terms of insulation, the R-value helps builders and homeowners select appropriate materials to ensure desired thermal performance. Understanding R-values is essential when designing energy-efficient structures, as it aids in optimizing both comfort and energy cost savings.

The other options focus on different concepts related to temperature and energy efficiency but do not directly relate to the fundamental purpose of R-value. For instance, measuring temperature differences or thermal resistance of windows does not encapsulate how well a material insulates in general terms. Similarly, evaluating energy efficiency in HVAC systems involves a wider scope of factors beyond just a material's insulating ability.