K_TO_R_VALUE

Converts thermal conductivity to insulation R-value per inch in either SI or Imperial conventions. This enables direct comparison with building-material specifications.

Conceptually, the conversion is the inverse of conductivity with a unit-system scaling factor:

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

Excel Usage

=K_TO_R_VALUE(k, SI)

k (float, required): Thermal conductivity (W/m/K).
SI (bool, optional, default: true): Whether to return the SI R-value (-).

Returns (float): R-value (m^2K/(Winch) or ft^2degFh/(BTU*inch)).

Example 1: SI R-value example

Inputs:

k
0.2

Excel formula:

=K_TO_R_VALUE(0.2)

Expected output:

0.127

Example 2: Imperial R-value example

Inputs:

k	SI
0.2	false

Excel formula:

=K_TO_R_VALUE(0.2, FALSE)

Expected output:

0.721139

Example 3: Higher conductivity example

Inputs:

k
1.5

Excel formula:

=K_TO_R_VALUE(1.5)

Expected output:

0.0169333

Example 4: Low conductivity in imperial

Inputs:

k	SI
0.05	false

Excel formula:

=K_TO_R_VALUE(0.05, FALSE)

Expected output:

2.88456

Python Code

Show Code

from ht.conduction import k_to_R_value as ht_k_to_R_value

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

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

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

    Args:
        k (float): Thermal conductivity (W/m/K).
        SI (bool, optional): Whether to return the SI R-value (-). Default is True.

    Returns:
        float: R-value (m^2*K/(W*inch) or ft^2*degF*h/(BTU*inch)).
    """
    try:
        return ht_k_to_R_value(k=k, SI=SI)
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

k *

Thermal conductivity (W/m/K).

Whether to return the SI R-value (-).