Aspects of the technology relate to temperature regulation for high altitude, long duration balloons, such as balloons that operate in the stratosphere for weeks, months or longer. A balloon covering overlays the balloon envelope, providing an opaque or otherwise light-reflective layer with low emissivity that blocks or reflects optical and/or infrared light. Heat from within the envelope is reflected back from the covering toward the envelope, while light from the sun is reflected back towards the environment. An active venting system is employed to draw in cooler ambient air from the external environment while expelling warmer air from within the envelope. Vent and air intake assemblies of the active venting system are actuated in view of current and/or predicted balloon conditions to regulate internal balloon temperature. This approach reduces repeated pressure changes, which can put undue stress on the balloon envelope and adversely affect the operational lifespan of the system.