Calculating R-Values

Calculating R-Values for Walls

To calculate the most accurate heat loss, we should know the R-Value. Calculating R-values is not a tough job. The hardest part of this job is acquiring an infrared thermometer if you don't have one. Maybe you can borrow one from a friend, or an HVAC guy, or even rent one for a day. R-value is the resistance the heat encounters as it leaves the structure. This is known as heat loss. We calculate the heat loss accurately to size heating and cooling equipment. When the appliances are properly sized, they operate cheaply and have fewer maintenance problems. Let's see how to calculate R-values. The outdoor temperature should be at least 15f colder or warmer than the interior temperature. The greater the temperature difference, the more accurate it is. There will not be drastic change from the interior to exterior temperature from 15f to 40f.

What you will need for the calculations

1. An Infrared Thermometer and a regular thermometer
2. Blank Worksheet
3. Pencil or Pen
4. A calculator, if you do not want to do simple math
5. Blank R-Value Chart

Gathering Information

We must take some temperature readings.

1. Make sure there is at least a 15f difference between inside and outside temperatures
2. Measure the air temperature of the room. Measure in the center of the room as the room temperatures change
3. Measure the temperature of an interior non-sunny wall about 3 ft above the floor
4. Measure the exterior wall approximately in the same place as the interior measurement
5. Do the math
6. Plot the information on the R-Value chart

Sample Worksheet

Sample R-Value Chart

Living Room from above worksheet columns 5 & 6

Blank Worksheet Blank R-Value Chart

Disclaimer: The information found on this website is for informational purposes only. All preventive maintenance, service, and installations should be reviewed on a per-job basis. Any work performed on your heating system should be performed by qualified and experienced personnel only. Comfort-Calc or its personnel accepts no responsibility for improper information, application, damage to property, or bodily injury from applied information found on this website. As a professional, you should review it.