1. What is R-value?

R-value is a measure of thermal resistance used in the building and construction industry. The higher the R-value, the greater the insulating effectiveness.

2. How Does the Calculator Work?

The calculator uses the R-value formula:

Where:

• \( R \) — Total thermal resistance
• \( \text{Thickness}_i \) — Thickness of material i (feet)
• \( k_i \) — Thermal conductivity of material i (BTU·ft/h·ft²·°F)

Explanation: The total R-value of a composite material is the sum of the R-values of each individual layer.

3. Importance of R-value Calculation

Details: Accurate R-value calculation is crucial for building energy efficiency, proper insulation design, and meeting building code requirements for thermal performance.

4. Using the Calculator

Tips: Enter the number of materials in your assembly, then for each material provide the thickness in feet and the k-value (thermal conductivity). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between R-value and U-value?
A: R-value measures thermal resistance, while U-value measures thermal transmittance. U-value is the reciprocal of R-value.

Q2: What are typical R-values for common insulation materials?
A: Fiberglass batts typically have R-3 to R-4 per inch, spray foam R-6 to R-7 per inch, and rigid foam boards R-4 to R-8 per inch.

Q3: Why is R-value important in building design?
A: Proper R-values help maintain comfortable indoor temperatures, reduce energy costs, prevent moisture condensation, and meet building code requirements.

Q4: Does R-value change with temperature?
A: Yes, most insulation materials have slightly different R-values at different temperatures, though this is typically minor for most applications.

Q5: How does air movement affect R-value?
A: Air infiltration can significantly reduce effective R-value. Proper air sealing is as important as insulation for energy efficiency.