根據熱力學定律，熱能會從高熱能向低熱能處傳遞，在夏季新鮮空氣中的高熱能會被轉移到熱交換輪上， 再從轉輪傳遞到室內排氣排至室外，使送入室內的新鮮空氣自然被降低溫濕度而維持室內空氣條件。能量傳遞的總數被定義為熱交換效率。
轉輪式熱交換器，熱交換效率通常維持在70%~90%。
The combination of heat and humidity recovery of rotary heat exchangers is a highly efficient energy-saving technology. It is common to have energy recovery rates between 70-90%. Air pressure drops through such exchangers of lower 200 Pa are usually economically sensible.
