We save energy! Therma-Fuser VAV diffusers are energy efficient VAV diffusers that produce 15% to 47% energy savings. Acutherm manufactures components for heating and air conditioning systems that make commercial buildings more comfortable, save energy, offer sustainability and can also reduce total installed costs. Our components are called Therma-FuserTM variable air volume (VAV) diffusers. They are used in VAV air conditioning systems which, instead of varying the temperature of the cooling air, vary the amount of the cooling air to maintain even room temperatures.