ROOF MATERIALS

GOAL:

To make students aware of various roofing materials and their role in making homes more energy efficient.

OBJECTIVES:

The student will be able to:

1. Name various types of roofs.

2. List advantages and disadvantages of each.

3. Describe various types of insulation products.

LESSON/INFORMATION:

The roof of your house is a shelter from rain, snow and sun. The surface of your roof will determine how your house looks as well as how effective a shelter it will be. How you relate your roof to the sky is very important. Pitched roofs, both low and steep are designed for shedding water and snow.

An Asphalt/Fiberglass shingle roof is one of the least expensive, is easy to install, has a fairly long life, and is attractive, but, it has very little value in reducing heat gain. Therefore the attic space should be well ventilated to the outside. Use continuous soffit and ridge vents whenever possible. You will need at least one square foot of free vent area for each 150 square feet of ceiling. Be sure that vents are sized to provide an equal open area for both inlets and exits. Anyone in south Louisiana installing an asphalt/fiberglass shingle roof should consider a fungus resistant roof. For $5.00 more per square you get a 30 year labor and material warranty on the roof.

Most believe that the only function of a roof covering is to provide a material to shed water, but of equal importance is its ability to provide thermal protection. In a house with a cathedral ceiling, the roof forms the ceilings of the rooms below. A dark colored shingle will affect the interior environment by absorbing solar heat from the sun during the day. This same roof, on a clear, cool night will transmit more heat from the house than would a light colored roof. A white or nearly white roof will reflect solar radiation during the day and will not radiate much heat at night. Unfortunately the roof has to stay relatively clean if it is to function properly.

INSULATION

If thermal insulation is required under an asphalt/fiberglass shingle roof, choose a type that will suit your needs. Insulation comes in blankets (rolls make of glass fiber), batts (pre-cut blankets in standard sizes), fiberglass (loose insulation requiring blown-in installation), cellulose fiber (recycled paper particles treated with chemicals and blown-in or sprayed), foam-in-place (liquid foamed plastic), phenolic or rigid foam (sheets or board of foamed plastic such as polyurethane or polystyrene). When choosing the insulation for your job, consider such factors as cost, quality, special characteristics (e.g. odor, treatment for insects, etc.), and insulating capability (R-value). Refer to the table charts further down on this page for insulation comparisons.

It is essential that insulation be properly installed. Follow the manufacturer's instruction to achieve the desired thermal performance. An R-11 fiberglass batt will perform at less than R-7 if compressed half the desired thickness. Insulation that is blown or poured into an attic will not perform to its stated standards unless it is evenly applied to the proper depth and density. The goal of any installation is to have a continuous layer of insulation without gaps, cracks or air bypasses.

METAL ROOFS:

A metal roof has many advantages such as light weight, rigidity, a variety of shapes, colors, textures, and it is not degraded by the sun. Metal roofs also have a long life and they are adaptable to many building designs. The biggest advantage is being a positive slope for draining. If thermal insulation is required in a metal roof system, it must be located below the metal.

Metal roofs, however, could develop leaks if joints are not watertight and if screws are not properly installed. The metal roof is also subject to wind damage if not properly secured. It is also not widely accepted in some areas.

CLAY TILE ROOFS:

Although it is not used a great deal in this area, a clay tile roof is an excellent roofing material and is very energy efficient. A modified version of this roof is the Supradur (Tegusol) clay roof tile. It is composed of fiber and concrete material instead of clay.

Besides being energy efficient, clay tiles are fireproof, long lasting, and attractive. However, the cost is three times as much as asphalt/fiberglass shingles. Clay tiles are better suited for hot, dry climates rather than rainy climates where they could develop leaks. Clay tile roofs are also very heavy and cost more to install.

ACTIVITY 1:

Answer the questions.

1. Provides shelter:

2. Provided movement of air:

3. Most popular type of roof covering (two words):

4. Material that helps to control interior temperatures:

5. One of the first manufactured roofing materials:

6. The opposite of reflect:

ACTIVITY 2:

Put several different colored asphalt/fiberglass shingles outside on a sunny afternoon. After the shingles have been exposed to the sun for a while, have the students put their hands above each shingle. Have them write down their findings and the conclusion they reach from this experiment. Discuss their findings in class.

ACTIVITY 3:

Fill in the blanks using the information from the lesson.

1. A white roof will _______ solar radiation during the day.

2. The first manufactured roofing material was _______.

3. A _______ is very energy efficient.

4. _______ or _______ shingles have little value in reducing heat gain from a building.

5. A dark colored shingle will _______ solar heat.

6. A _______ roof is ideal for retaining rain.

7. The goal of installing insulation is to have a continuous layer of insulation without any _______.

8. _______ roofs are excellent for shedding water.

9. _______ roofs are adaptable to many building designs.

10. A _______ roof will not radiate much heat at night.

11. The biggest advantage of a metal roof is: _______.

ACTIVITY 4:

Have the students make a chart showing the advantages and disadvantages of three types of roof coverings.

INFORMATION CHECK:

Please indicate whether the following statements are TRUE or FALSE.

_______ 1. A dark roof will absorb solar heat from the sun during the day.

_______ 2. A flat roof has little water shedding ability.

_______ 3. Asphalt/fiberglass shingles have a high value in reducing heat gain from a building.

_______ 4. A white roof will not radiate much heat at night.

_______ 5. A metal roof is not degraded by the sun.

_______ 6. Clay tile roofs are ideal for the Louisiana climate.

_______ 7. A dark roof, on a clear, cool night will transmit less heat from the house than a light colored roof.

_______ 8. Pitched roofs are excellent for shedding rain and snow.

_______ 9. The biggest advantage of a metal roof is its rigidity.

______ 10. Asphalt/fiberglass shingle roof is not degraded by the sun.

______ 11. When installing insulation, you should follow the manufacturer's instructions to achieve the desired thermal performance.

ANSWERS TO ACTIVITY 1:

1. roof

2. ventilated

3. asphalt shingle

4. insulation

5. metal

6. absorb

ANSWERS TO ACTIVITY 3:

1. reflect

2. metal

3. clay tile roof

4. asphalt/fiberglass shingles

5. absorb

6. flat

7. gaps

8. pitched

9. metal

10. white

11. a positive slope for drainage

ANSWERS TO ACTIVITY 4:

ANSWERS TO TRUE/FALSE:

1. True

2. True

3. False

4. True

5. True

6. False

7. False

8. True

9. False

10. False

11. True

REFERENCES:

SLEMCO's Builder's Guide - Design One Homes - for Energy-Efficient Construction.

Comments or questions to: TechAsmt@LA.GOV

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