How to Understand Insulation R-Value How to Understand Insulation R-Value

The insulation r-value measures the effectiveness of a material in preventing heat flow between two areas. Standard building materials have lower R-values (e.g. brick: 0.2, hard wood: 0.71), so additional insulation materials might be required to effectively preserve heat.

The R-values for common building insulators can vary from 2.7 to 6.2. For instance, loose-fill rockwool has an insulation R-value of 2.7 to 3.0, fiberglass batt has an R-value of 2.9 to 3.8, while other materials have a higher coefficient: high performance fiberglass batts have an insulation r-value ranging from 3.7 to 4.3 and polyurethane foam: 5.6 to 6.2.

If you live in a warmer climate, it does not mean that your house does not need insulation. An appropriate R-value insulator helps you save money you normally spend for heating or cooling your house by maintaining a constant temperature. You can easily determine the R-values for your house’s insulation without having to tear down the walls and look for the insulation material.

You Will Need:

  • Pen

  • Paper

  • Infrared thermometer

  • R-value chart

Step 1 – Measure the Air Temperature

Set the infrared thermometer to display the temperature in Fahrenheit degrees. Go near an interior wall or a piece of furniture and measure their surface temperature. Make sure the surface you chose is not in the sunlight, nor close to a heating or cooling device. Put the temperature value on the piece of paper. Mark it as “air temperature”.

Step 2 – Measure Outside Wall Temperature

Pick an exterior wall that is easily accessible both from the inside and from the outside of your house. The wall should not be in direct sunlight. Measure the surface temperature of the wall on the outside. Write the value of the temperature on the piece of paper and mark it “exterior wall temperature: outside”.

Step 3 – Measure the Inside Wall Temperature

Measure the temperature of the same exterior wall from the inside. Try to locate approximately the same area you measured from the outside. Write down the temperature and mark this reading “exterior wall temperature: inside”.

Step 4 – Establish Exterior Wall Temperature Difference

Calculate the difference between “exterior wall temperature: outside” and “exterior wall temperature: inside”. Subtract the smaller value from the larger value and write down the result, marking it “exterior wall temperature difference: outside and inside”.

Step 5 – Establish Interior Temperature Difference

Repeat the calculations, using the “exterior wall temperature: inside” and the “air temperature”. Mark down the result as “interior temperature difference: air and wall”.

Step 6 – Compare Results

Compare your results with an R-value chart. Determine the intersection point of the two temperature differences you measured (“exterior wall temperature difference: outside and inside” and “interior temperature difference: air and wall”) by drawing lines on the chart. The value on the chart which is closest to the intersection point you drew gives you the R-value for the insulation of your house. The end result can be anywhere between R2 and R20.

Step 7 – Compare Your Insulation R-value with Official Recommendations

Compare the insulation R-value of your house to the official recommendations for your area. Different climate areas require different R-values. In case your house’s insulation needs improvement, take into consideration moisture movement and air leakage as well. The R-values of the building and insulating materials are not enough to determine the best insulating option. 

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