Less Is Cool

Objects absorb heat and restrict airflow, making any room hot. Air heats and cools faster than objects, but it doesn't retain the temperature. Most objects including, furniture, linens and knickknacks absorb heat and then re-radiate it into the air, raising the temperature. If you want to keep your home or work space cooler in the summer, keep your shades closed/down, unclutter stuff that you really do not need, and replace your incandescent light bulbs with CFLs (compact fluorescent light bulbs) and EDs which generate less heat.

https://www.explainthatstuff.com/heat.html