When cooling a room with a box fan, placing it on the floor is generally more effective than putting it high on a shelf. This is because of how fans work and the principles of heat distribution.
The primary purpose of a fan is to circulate air and create airflow within a space. When the fan is on the floor, it is better positioned to draw in the cooler air from ground level and push it upward, creating better air circulation throughout the entire room. This helps in mixing the cooler air from the lower part of the room with the warmer air near the ceiling, resulting in a more even temperature distribution.
When you place a fan high on a shelf, it may not effectively circulate the air throughout the room. Instead, it may create a localized draft in the immediate vicinity of the shelf, which might not have a significant impact on the overall temperature of the room. The warm air tends to rise and can get trapped near the ceiling, making the upper part of the room warmer while the lower part remains relatively cooler.
Additionally, placing the fan on the floor allows it to draw in cooler air from nearby windows or doors, which is particularly beneficial during cooler times of the day, such as in the early morning or late evening when outdoor temperatures drop.
However, for best results, you can also consider using multiple fans strategically placed around the room to enhance the overall air circulation and cooling effect. Ceiling fans can also be quite effective in pushing warm air downward during the colder months and providing a breeze during the warmer months.