Which of the following statements is true about HRVs?

Heat Recovery Ventilators (HRVs) are designed to improve indoor air quality while maintaining energy efficiency. The statement that they transfer only heat without moisture is accurate because HRVs operate by circulating air through a heat exchange core, where outgoing air transfers its heat to incoming air. This process significantly reduces energy loss while providing fresh, tempered air to the indoor environment.

In addition to heat, though, HRVs also help manage humidity levels, but they do not transfer moisture in the same manner as Energy Recovery Ventilators (ERVs), which can transfer both heat and moisture. The function of HRVs is particularly beneficial in climates where maintaining indoor humidity levels is essential but not necessarily in balancing moisture transfer.

The other options do not accurately describe HRVs. They require electrical power to operate, can be effectively used in colder climates, and do not need manual adjustments typically since they are designed to operate automatically based on interior and exterior air conditions. Hence, the choice highlighting their specific function regarding heat transfer is the right one.