Nevertheless, it is always wise to insulate your basement walls with R-10 to R-19 insulating material. This helps to make the basement more energy-efficient.
Your existing cooling unit probably manages to keep the basement comfortable on hot summer days; however, a basement window air conditioner will cool the room further.
Homeowners who are finding it hard to keep the basement cool during summer should contact an HVAC contractor for further advice. The engineer may suggest you install a more powerful air conditioning system, or he may feel you need to install portable window air conditioner.