Question

How does vacuum reduce thermal energy transfer

Answer 1

Less air pressure.

Step-by-step explanation:

Thermal energy travels in many different ways and one of those ways is through the air so if there's less air, it would reduce thermal energy transfer.

Answer 2

The silver coating on the inner bottle prevents heat transfer by radiation, and the vacuum between its double wall prevents heat moving by convection. The thinness of the glass walls stops heat entering or leaving the flask by conduction.