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R-Value Calculator
Calculate the R-values and U-values of various materials based on your input for thermal conductivity, thickness, and material type.
Get accurate results with this simple, yet powerful tool.

Total Values | |
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Name: | |
Total R-Value: | -- ft²·°F·hr/Btu |
Total U-Value: | -- ft²·°F·hr/Btu |
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Variables
Material Type + Thickness, Thermal Conductivity & Layers
Material Type
The type of material significantly impacts its thermal resistance, as different materials conduct heat at varying rates.
Material Thickness
The thickness of a material directly affects its R-value, with thicker layers generally providing better thermal resistance.
Thermal Conductivity
Thermal conductivity measures how easily heat passes through a material, with lower values indicating better insulation properties.
Number of Layers
Many designs include multiple material layers, such as insulation, drywall, and exterior cladding, each contributing to the total R-value.
R-Value Formula
The R-value measures a material's thermal resistance, indicating how effectively it resists heat flow.
It is calculated using the following equations in both imperial and metric:
Imperial Equation
Following the formula below, you can calculate the R-value:
Components
- = Thermal resistance (ft²·°F·hr/BTU)
- = Material thickness (inches, in)
- = Thermal conductivity of the material (BTU·in/hr·ft²·°F)
In the imperial system, the R-value is calculated by dividing the material's thickness (in inches) by its thermal conductivity (in BTU·in/hr·ft²·°F). Higher values indicate superior insulation properties.
Metric Equation
Following the formula below, you can calculate the R-value:
Components
- = Thermal resistance (m²·K/W)
- = Material thickness (meters, m)
- = (Lambda) Thermal conductivity of the material (W/m·K)
In the metric system, the R-value is determined by dividing the material's thickness (in meters) by its thermal conductivity (in watts per meter per Kelvin). A higher R-value indicates better insulation performance.
What is the R-Value Calculation Used For and Why is it Important?
The R-value calculation measures how well a material resists heat transfer, making it essential for evaluating insulation performance.
It's commonly used by engineers and architects to ensure buildings meet energy efficiency standards and maintain comfortable indoor temperatures.
By calculating R-values, you can determine the right combination of materials to reduce heat loss and energy costs.
This is especially important in designing HVAC systems, where accurate insulation values impact heating and cooling efficiency.
Proper R-value calculations also contribute to compliance with building codes and sustainability goals.
Ultimately, using accurate R-value calculations helps create buildings that are cost-effective, comfortable, and environmentally responsible.
h2x for R-Value Calculations
- Automate all of the duct and fan sizing based on your design layout
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- Download a comprehensive list of Bill of Materials
h2x is CIBSE-verified design software built to improve the efficiency and quality of your design process. Read more.
Why Use a R-Value Calculator?
Evidently, there are several benefits of using an online calculator to calculate the R-value, including:
Increased Accuracy:
Determine accurate values by eliminating the possibility of human error when calculating air pressure drop by hand.
Time-Saving:
Saves time by providing quick and easy calculations, putting an end to performing complex mathematical calcs manually.
Easy to Use:
User-friendly and requires no special training or technical knowledge. Just provide the input and read the results.
Cost-Effective:
Can save money by reducing the number of time spent on manual and long calculations, and avoiding costly mistakes.
Frequently Asked Questions
Resources
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