Humidifying without adding humidity: Psychrometric shifts in humidity from air temperature setbacks enabled by radiant heating or cooling

Abstract

Active humidification of the indoor environment is both expensive and cumbersome to add on top of existing air-conditioning systems. To ensure occupant comfort and health in the indoor environment, it is often important to add humidification components, particularly when the heating demand is high and the absolute moisture content in the air is coincidentally low. Conventional wisdom dictates that to increase relative humidity in the indoor environment, moisture must be added to the air. We propose an alternative method that relies on the co-benefit of radiant systems: being able to condition to lower air temperature during heating season and higher temperature during cooling season (thereby reducing the required dehumidification). This paper presents results from a preliminary study from discussions on the humidification effect without actively adding moisture, or how the air condition shifts on the psychrometric chart when radiant heating or cooling is used instead of all-air systems. Building on existing literature that have already showed the energy and comfort benefit of using radiant systems w i t h i n the indoor environment, we hope to demonstrate the magnitude of the problem across the United States through a geographical study based on averaged weather data across the country in 2018.