Insulation R-Value Calculator

What is R-Value in Insulation?

R-value measures thermal resistance, meaning how well insulation resists heat flow. The higher the R-value, the better the insulation performance.

For example:

• R-13 → basic insulation
• R-30 → good insulation
• R-49 → high-performance insulation

🧮 R-Value Formula (Used in Calculator)

$R_{total} = R_1 + R_2 + R_3 + \cdots + R_n$Rtotal​=R1​+R2​+R3​+⋯+Rn​

Each layer contributes to total insulation.
If thickness is involved:$$R = (\text{R per inch}) \times (\text{Thickness})$$R=(R per inch)×(Thickness)

👉 Then all layers are added together.

This is exactly how real construction calculations work.

🏠 Why R-Value Matters

• Reduces energy bills
• Improves indoor comfort
• Prevents heat loss/gain
• Meets building codes

Higher R-value = better energy efficiency.

📌 Common R-Values Per Inch

🧠 Example Calculation

If you have:

• Fiberglass (R 3.5/inch, 6 inches)
• Foam (R 6/inch, 2 inches)

Total:$$(3.5 × 6) + (6 × 2) = 21 + 12 = R-33$$(3.5×6)+(6×2)=21+12=R−33

❓ FAQ

What is a good R-value for insulation?

Depends on climate, but generally:

• Walls: R-13 to R-21
• Attic: R-30 to R-60

Can you combine insulation layers?

Yes — R-values add together, which is exactly what this calculator does.

What is the difference between R-value and U-value?

• R-value = resistance
• U-value = heat transfer
• Formula: U = 1 / R