What type of air economizer is required when 40% RH is maintained indoors in all seasons?

• A. Natural air economizer
• B. Outdoor air economizer
• C. Mechanical economizer
• D. Restrictive economizer

Answer: (B)

When maintaining a relative humidity (RH) of 40% indoors in all seasons, an outdoor air economizer is the most suitable choice. An outdoor air economizer works by using outdoor air to help cool or ventilate indoor spaces, utilizing the naturally low humidity of outdoor air, particularly in certain seasons. This method helps to achieve energy savings by reducing the reliance on mechanical cooling systems, which can contribute to excess humidity indoors.

In cooler months or seasons when outdoor air is dry, the outdoor air economizer can draw in this air to maintain desired indoor conditions without excessive energy consumption from heating or cooling systems. The consistent application of outdoor air also aids in managing humidity levels, ensuring that the indoor environment remains comfortable by preventing it from becoming too damp.

Other economizer types may not effectively meet the specific requirement of maintaining 40% RH indoors across all seasons. For example, a natural air economizer generally relies on passive ventilation methods and may not provide the controlled climate needed year-round. Mechanical economizers introduce outdoor air but can be less efficient in humidity control. A restrictive economizer, on the other hand, is designed to limit air flow, which would not facilitate the necessary humidity management needed to maintain 40% RH indoors effectively. Thus, the outdoor