The sol-air temperature, also known as the ambient temperature, is the temperature of the air surrounding a building or structure. It is influenced by several factors, including the outside air temperature, intensity of solar radiation, absorptivity of the wall, convective heat transfer coefficient at the outer surface of the wall, and the indoor design temperature. Let's discuss each of these factors in detail:

1. Outside Air Temperature:
The sol-air temperature is directly affected by the outside air temperature. If the outside air temperature is high, the sol-air temperature will also be high, and vice versa. The outside air temperature is typically determined by the prevailing weather conditions, such as the season, time of day, and location.

2. Intensity of Solar Radiation:
Solar radiation refers to the energy emitted by the sun, and its intensity can vary throughout the day and year. The amount of solar radiation absorbed by the building's walls affects the sol-air temperature. If the walls have a high absorptivity, they will absorb more solar radiation, leading to an increase in the sol-air temperature.

3. Absorptivity of Wall:
The absorptivity of the wall refers to its ability to absorb solar radiation. A wall with a high absorptivity will absorb more solar radiation, resulting in a higher sol-air temperature. The absorptivity of a wall depends on its color, material, and surface properties.

4. Convective Heat Transfer Coefficient at Outer Surface of Wall:
Convective heat transfer occurs when heat is transferred between a solid surface and a fluid (in this case, air) due to the motion of the fluid. The convective heat transfer coefficient at the outer surface of the wall determines the rate at which heat is transferred between the wall and the surrounding air. A higher convective heat transfer coefficient will result in a faster exchange of heat and can affect the sol-air temperature.

5. Indoor Design Temperature:
The indoor design temperature is the desired temperature inside the building. It is typically set based on comfort requirements. The sol-air temperature can indirectly influence the indoor design temperature as heat transfer between the indoor and outdoor environments occurs through the building envelope.

In conclusion, the sol-air temperature depends on several factors, including the outside air temperature, intensity of solar radiation, absorptivity of the wall, convective heat transfer coefficient at the outer surface of the wall, and the indoor design temperature. All of these factors play a role in determining the overall thermal behavior and comfort of a building or structure.