# White Roof Vs. Black Roof on a house

• Dreebs
In summary: By reflecting away sunlight, the roof helps reduce the amount of heat transferred to the house from the sun. In addition, by emitting its own thermal radiation almost perfectly, the roof helps send its excess heat into the sky and space.
Dreebs

## Homework Statement

Your house will have a white roof, rather than the traditional black roof. A white roof reflects 90% of sunlight (its high-temperature emissivity is almost 0) but emits its own thermal radiation with almost perfect efficiency (its low-temperature emissivity is almost 1). How does that help keep your house (and your city) cool during the summer? Select one:
a. The roof is white across the entire electromagnetic spectrum, so it doesn't exchange heat via thermal radiation.
b. By reflecting away sunlight, your roof reduces the heat transferred to your house (and your city) from the sun. By emitting its own thermal radiation almost perfectly, your roof helps you house send its excess heat into the sky and space.
c. Although the roof looks white, the fact that it emits its own thermal radiation so well means that it is actually black across the entire electromagnetic spectrum. Black surfaces stay cooler in sunlight than do white surfaces.
d. The white roof is a poorer conductor of heat than a black roof, so it keeps your house cool.

N/A

## The Attempt at a Solution

B, The white roof reflects much of the sunlight thus reducing the amount of heat transferred to your house.

Philip Robotic
Dreebs said:

## Homework Statement

Your house will have a white roof, rather than the traditional black roof. A white roof reflects 90% of sunlight (its high-temperature emissivity is almost 0) but emits its own thermal radiation with almost perfect efficiency (its low-temperature emissivity is almost 1). How does that help keep your house (and your city) cool during the summer? Select one:
a. The roof is white across the entire electromagnetic spectrum, so it doesn't exchange heat via thermal radiation.
b. By reflecting away sunlight, your roof reduces the heat transferred to your house (and your city) from the sun. By emitting its own thermal radiation almost perfectly, your roof helps you house send its excess heat into the sky and space.
c. Although the roof looks white, the fact that it emits its own thermal radiation so well means that it is actually black across the entire electromagnetic spectrum. Black surfaces stay cooler in sunlight than do white surfaces.
d. The white roof is a poorer conductor of heat than a black roof, so it keeps your house cool.

N/A

## The Attempt at a Solution

B, The white roof reflects much of the sunlight thus reducing the amount of heat transferred to your house.
Yes, but the second part of the explanation provided in option b is also important.

Philip Robotic

## 1. What are the benefits of a white roof over a black roof on a house?

White roofs reflect more sunlight and heat than black roofs, resulting in lower energy costs for cooling the house. They also have a longer lifespan and can help reduce the urban heat island effect in cities.

## 2. Does a white roof require more maintenance than a black roof?

No, white roofs do not require more maintenance than black roofs. In fact, they may require less maintenance as they do not absorb as much heat and UV rays, which can cause deterioration over time.

## 3. Are there any disadvantages to having a white roof on a house?

One disadvantage of a white roof is that it may show dirt and stains more easily than a black roof. Additionally, in colder climates, a white roof may not be as effective in retaining heat during the winter months.

## 4. Can a black roof be just as energy efficient as a white roof?

Yes, a black roof can be just as energy efficient as a white roof if it is made with reflective materials or has a high solar reflectance index (SRI). However, white roofs are generally more energy efficient due to their natural reflective properties.

## 5. How do I determine which color roof is best for my house?

The best color roof for your house will depend on your climate and personal preferences. In hot climates, a white roof may be more beneficial for energy efficiency, while in colder climates, a black roof may help retain heat. It is important to also consider the material and quality of the roof in addition to the color.

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