Cool cap for outdoor heat exchangers

A new apparatus, which may be referred to as a "cool cap," for use with an outdoor heat exchanger (e.g., a heat pump or an air conditioning condenser) having an air inlet vent and an air outlet vent, the apparatus comprising a top having an exhaust vent complementary to the air outlet vent; and a surrounding wall attached to the top, wherein the surrounding wall is at least about eight inches from the outdoor heat exchanger upon installation, and wherein the surrounding wall has an intake opening having an airflow being equal to or greater than the exhaust vent and forming a substantially unimpeded air pathway through the apparatus through the outdoor heat exchanger and out the exhaust vent; wherein the surrounding wall and top are thermally insulating.