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How to Select Cool Roofs


Quiz Questions

1.Just as wearing light-colored clothing can help keep a person cool on a sunny day, cool roofs use solar-reflective surfaces to maintain lower roof temperatures.
True
False
2. Traditional dark roofs can reach temperatures of _________ or more in the summer sun. A cool roof under the same conditions could stay more than _________ cooler.
150°F, 50°F
300°F, 200°F
100°F, 30°F
3.There are several reasons why building owners could benefit from cool roofs. Cool roofs may potentially:
reduce energy bills by decreasing air conditioning needs.
improve indoor thermal comfort for spaces that are not air conditioned.
decrease roof operating temperature, which may extend roof service life.
All above
4.Figure 5 shows:
Although white materials tend to be very good solar reflectors, colored roofing materials, can also be made to reflect more sunlight.
Various color tiles
5.Roof systems are made of one or more material layers. The surface exposed to the sun is the one that determines if a roof is cool or not.
True
False
6.Cool Roof Coatings contain white or special reflective pigments that reflect sunlight. Coatings are like very thick paints that can protect the roof surface from ultra-violet (UV) light and chemical damage, and some offer water protection and restorative features as well. Coatings can extend a roof’s service life as long as the roof is still in good condition, Figure 6. More than 500 different cool roof coatings are available, and products exist for most roof types. Manufacturers also coat some roof surfacing materials (membranes, metals, granules, etc.) at the factory to make them more reflective.
True
False
7.Built-Up Roofs consist of a base sheet, fabric reinforcement layers, and a protective surface layer that is traditionally dark. The surface layer can be made in a few different ways, and each has cool options. One way involves embedding mineral aggregate (gravel) in a flood coat of asphalt. By substituting reflective marble chips or gray slag for dark gravel you can make the roof cool. A second way built-up roofs are finished is with a mineral surfaced sheet. These can be made cool with reflective mineral granules or with a factory-applied coating. Another surface option involves coating the roof with a dark asphaltic emulsion. This type can be made cool by applying a cool coating directly on top of the dark emulsion.
True
False
8. Metal Roofs are available with natural metallic finishes, oven-baked paint finishes, or granular coated surfaces. Usually, unpainted metals are good solar reflectors but poor thermal emitters so they rarely satisfy low slope cool roof requirements, though some may still have a high enough SRI to count as a cool roof. Paint applied at the factory or in the field can increase a metal roof’s solar reflectance and thermal emittance, allowing it to achieve cool roof status. Alternatively, cool reflective coatings can be applied as with low sloped metal roofs.
True
False
9.Tile Roofs can be made of clay, slate, or concrete. Clay and slate tiles come from the ground, so their colors differ depending on the earth’s composition. Some varieties will naturally be reflective enough to achieve cool roof standards. Tiles can be also be glazed to provide waterproofing or coated to provide customized colors and surface properties. These surface treatments can transform tiles with low solar reflectance into cool roof tiles.
True
False
10.A cool roof need not cost more than a non-cool roof. Major roof costs include upfront installation (materials & labor) and ongoing maintenance (repair, recoating, and cleaning).
True
False
11.In general, typical approximate installed roof cost premiums for different cool roof options are given in Tables 5 and 6. The premiums equal the additional cost you can expect to pay for a cool product. For example, if you are planning to install a mineral-surfaced modified bitumen roof, the table indicates you might expect to pay $0.50/ft2 more for a cool roof with the same kind of surface.
True
False
12.Which of the following could result from installing a cool roof?
Energy savings.
Rebates and incentives.
HVAC equipment downsizing.
Extended roof lifetime.
All above
13. According to Figure 8: US Climate Zones, in what zones are cool roofs highly recommended for buildings?
Zones 1-3
Zones 1-5
14.Cool roofs may add only marginal energy savings to buildings that are already highly energy efficient. Highly efficient buildings are often well insulated to minimize the flow of heat through the walls and roof. This helps the occupied space stay cool in summer and warm in winter, regardless of the roof’s surface temperature. However, dark roofs on well-insulated buildings can become very hot, so cool roofs help achieve the environmental benefits associated with lower roof temperatures. Keeping a roof cool may also extend its lifetime.
True
False
15.Solar energy systems, such as photovoltaic (PV) panels and solar thermal collectors, absorb solar energy and can become hot in the sun. Solar equipment mounted flush with the roof’s surface can act like a dark roof, transmitting heat to the building and increasing air conditioning demand. Physical gaps between the solar equipment and roof can reduce this effect, since airflow through the gap can remove some of the heat that would otherwise flow into the roof. On permanently shaded portions of the roof, the roof’s solar reflectance does not affect air conditioning demand. This includes regions of the roof that are completely shaded by solar panels.
True
False