scope:

FOREWORD

Mold and microbial growth in buildings has been a persistent problem and health concern in all parts of the world. In 2019, the ASHRAE Board of Directors approved a major change to ASHRAE Standard 62.1 to reduce the risks of mold and moisture accumulation in mechanically cooled buildings. ASHRAE Standard 62.1-2022, Section 5.12, now instructs designers of ventilation systems to provide equipment and controls that limit the indoor air dew point to a maximum of 60°F (15°C) during both occupied- and unoccupied-mode operation.

However, problem of dampness and mold sometimes also occurs in buildings cooled by direct evaporation into the supply air. At present, Standard 62.1 does not address these risks, and the recent ASHRAE publication Damp Buildings, Human Health and HVAC Design makes it clear that damp buildings remain a concern for human health.

In light of that concern, the SSPC 62.1 considered the most appropriate way for designers to limit humidity in buildings and spaces served by direct evaporative cooling equipment.

A large proportion of evaporatively cooled buildings are industrial facilities and warehouses. These are rarely (if ever) overcooled. Condensation is less of a concern for buildings that have relatively warm indoor surfaces. That said, it must be admitted that if uncontrolled, some configurations of direct evaporative equipment can and sometimes do oversaturate the indoor air, leading to moisture absorption, accumulation, and building dampness.

However, evaporative cooling saves energy and provides appropriate thermal comfort at higher, more economical indoor air temperatures in hundreds of thousands of buildings all over the world. So while excessive dampness remains a concern, the energy-saving and comfort benefits of direct evaporative cooling should not be limited by a low dew point that applies to buildings held at cooler temperatures by mechanical cooling. Surface temperatures of materials inside evaporatively cooled buildings are typically quite warm compared to those in mechanically cooled buildings, so the risk of persistent dampness is lower. Therefore, limiting the indoor relative humidity rather than the dew point would be a more energy appropriate strategy.

Note: In this addendum, changes to the current standard are indicated in the text by underlining (for additions) and (for deletions) unless the instructions specifically mention some other means of indicating the changes.