R_VALUE_TO_K

Converts insulation R-value per inch into thermal conductivity, supporting both SI and Imperial R-value definitions. It is useful when translating building-material specs into engineering heat-transfer models.

The relationship is inverse with unit-dependent scaling:

k \propto \frac{1}{R_{\text{value}}}

Excel Usage

=R_VALUE_TO_K(R_value, SI)

R_value (float, required): R-value (m^2K/(Winch) or ft^2degFh/(BTU*inch)).
SI (bool, optional, default: true): Whether the R-value is in SI units (-).

Returns (float): Thermal conductivity (W/m/K).

Example 1: SI R-value example

Inputs:

R_value
0.12

Excel formula:

=R_VALUE_TO_K(0.12)

Expected output:

0.211667

Example 2: Imperial R-value example

Inputs:

R_value	SI
0.71	false

Excel formula:

=R_VALUE_TO_K(0.71, FALSE)

Expected output:

0.203138

Example 3: Larger SI R-value

Inputs:

R_value
0.25

Excel formula:

=R_VALUE_TO_K(0.25)

Expected output:

0.1016

Example 4: Imperial reference value

Inputs:

R_value	SI
1	false

Excel formula:

=R_VALUE_TO_K(1, FALSE)

Expected output:

0.144228

Python Code

Show Code

from ht.conduction import R_value_to_k as ht_R_value_to_k

def R_value_to_k(R_value, SI=True):
    """
    Convert R-value to thermal conductivity.

    See: https://ht.readthedocs.io/en/latest/ht.conduction.html

    This example function is provided as-is without any representation of accuracy.

    Args:
        R_value (float): R-value (m^2*K/(W*inch) or ft^2*degF*h/(BTU*inch)).
        SI (bool, optional): Whether the R-value is in SI units (-). Default is True.

    Returns:
        float: Thermal conductivity (W/m/K).
    """
    try:
        return ht_R_value_to_k(R_value=R_value, SI=SI)
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

R_value *

R-value (m^2*K/(W*inch) or ft^2*degF*h/(BTU*inch)).

Whether the R-value is in SI units (-).