EGEE 102
Energy Conservation and Environmental Protection

R-Value

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As you may recall from the first part of this lesson, R-value is a wall's capacity to resist heat loss or its thermal resistance. Insulation materials are rated in terms of their R-value, with a higher R-value indicating better insulating effectiveness.

The R-value of thermal insulation depends on the type of material, its thickness, and its density. Generally, walls are not made up of just one material or one layer.

R-values for most commonly used building materials are given in the table below. From looking at the table below, we can see that natural materials like stone and bricks are not good insulation materials, but most of the synthetic insulation products such as polystyrene or polyurethane are very effective insulation materials.

Building Materials and their R-Values
Material R-Value (ft2 o Fh / BTU)
Plain glass, 1/8 inch 0.03
Stone per inch 0.08
Common Brick per inch 0.20
Asphalt Roof Shingles 0.44
1/2 inch Gypsum Board (Drywall or plasterboard) 0.45
Wood Siding, 1/2 inch 0.81
Plywood, 3/4 inch 0.94
Insulating sheathing, 3/4 inch 2.06
Fiberglass, per inch (battens) 3.50
Polystyrene per inch 5.00
Polyurethane Board 6.25

If insulation materials have a low R-value per inch, then they will need to be thicker than those materials with a higher R-value per inch to achieve the same degree of effectiveness in resisting heat loss.

Look at the chart below to compare the thickness required of various insulation materials to achieve the same R-Value of 22 and then answer the questions below.

Thickness required of various insulation materials to achieve an R-Value of 22.
Thickness required of various insulation materials to achieve an R-Value of 22.
R-Value activity

Click here to open a text description of the R-Value activity.

R-Value of Insulation Materials

Consider four insulation materials: cellulose fiber, fiberglass, pine wood, and common brick. For each to have an R-value of 22, the thickness of each would need to be as follows:

  • Cellulose fiber: 6 inches
  • Fiberglass: 7 inches
  • Pine wood: 18 inches
  • Common brick: 110 inches

 

Using the previous information, answer the following questions.

1) Which insulation material needs the greatest amount of thickness for an R-value of 22?

a. Cellulose fiber

b. Fiberglass

c. Pine wood

d. Common brick

2) Is the insulation material you chose in question 1 natural or man-made?

a. Natural

b. Man-made

3) Which insulation material needs the least amount of thickness for an R-value of 22?

a. Cellulose fiber

b. Fiberglass

c. Pine wood

d. Common brick

4) Is the insulation material you chose in question 3 natural or man-made?

a. Natural

b. Man-made

 

Answers:

  1. D: Common brick
  2. A: Natural
  3. A: Cellulose fiber
  4. B: Man-made