There are several reasons why the inside of buildings can be cooler than the outside during summer, even without any active cooling systems:
Insulation: Buildings are typically constructed with materials that have insulating properties, such as thick walls, roofs, and windows. These materials help to slow down the transfer of heat from the outside to the inside. They act as a barrier to the external heat, preventing it from easily penetrating into the interior of the building.
Thermal Mass: Many buildings, especially those made of materials like concrete or brick, have a high thermal mass. Thermal mass refers to the ability of a material to store heat energy. During the day, when the outside temperature is high, the thermal mass of the building absorbs some of the heat. This helps to keep the interior cooler by delaying the transfer of heat into the building. The stored heat is then released slowly during the night when the outside temperature drops.
Shading: Buildings can be strategically designed with features such as overhangs, awnings, or trees planted around them to provide shading. These elements help to block direct sunlight from entering the building and reduce solar heat gain. By reducing the amount of solar radiation absorbed by the building, the interior temperature remains lower.
Natural Ventilation: Buildings often have windows and openings that allow for natural ventilation. When there is a breeze outside, opening windows or using cross-ventilation techniques can help draw in cooler air from the outside and expel warmer air from the interior. This natural airflow helps to maintain a more comfortable temperature inside the building.
Human Activity: The presence of people and their activities within a building can contribute to cooling. Humans generate heat through their metabolic processes and activities. In a well-ventilated building, this excess heat can dissipate, helping to keep the interior temperature lower.
It's important to note that while these factors can help to keep the interior of a building cooler than the outside in summer, the temperature difference may still be influenced by various factors, such as the design and construction of the building, its orientation, local climate conditions, and the duration and intensity of sunlight exposure.