1. What is Window Energy Rating?

Window Energy Rating is a measure of a window's thermal performance, calculated based on U-value, area, and temperature difference. It helps assess energy efficiency and heat loss through windows.

2. How Does the Calculator Work?

The calculator uses the energy rating formula:

Where:

• \( U \) — Thermal transmittance (W/m²K)
• \( A \) — Window area (m²)
• \( \Delta T \) — Temperature difference (K)

Explanation: The formula calculates the heat transfer rate through a window, with lower ratings indicating better energy efficiency.

3. Importance of Energy Rating

Details: Energy rating is crucial for building energy efficiency assessments, heating/cooling load calculations, and meeting building code requirements for thermal performance.

4. Using the Calculator

Tips: Enter U-value in W/m²K, window area in m², and temperature difference in Kelvin. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a good U-value for windows?
A: Lower U-values indicate better insulation. Modern energy-efficient windows typically have U-values between 0.8-1.8 W/m²K.

Q2: How does window area affect energy rating?
A: Larger window areas result in higher heat transfer, increasing the energy rating value and potentially reducing energy efficiency.

Q3: What temperature difference should I use?
A: Use the typical temperature difference between indoor and outdoor environments for your climate and season.

Q4: Are there other factors affecting window energy performance?
A: Yes, including solar heat gain coefficient, air leakage, frame material, and glazing type also impact overall energy performance.

Q5: How can I improve my window energy rating?
A: Use double/triple glazing, low-E coatings, insulated frames, and proper installation to improve energy efficiency.