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Architecture and Water Vapor
Why understanding building science is crucial
Posted on August 1, 2023 @ 5:42PM

Water is one of the most powerful forces of nature, and one of the primary variables determining the durability and performance of buildings. Depending on the climate, regional building design responds directly to rain, snow, and ice, but another powerful form in which water interacts with structures is vapor. 

The glass below shows behavior of water in all three phase states: solid, liquid, and vapor, the latter evidenced only as invisible moisture in the air that is condensing to a liquid state on the glass. In heated or cooled buildings water vapor is constantly moving through the building 'envelope' (exterior walls, roofs, and floors), just like thermal energy does. Humidity present in the interior and exterior climates travels between two atmospheres, always in the direction of the drier condition. 

The combination of water and thermal energy moving together in a dynamic balancing act is a crucial issue in building design. With a sudden change in temperature accompanied by sufficient moisture content in the air at any point, water will change from a vapor state to a solid state, just like the familiar appearance of water condensing on cold glass. When this occurs, hidden portions of buildings can become saturated with water, introducing the potential for mold, rot, and water damage to materials and connections.

In our work, we perform rigorous hygrothermal (moisture + thermal) analysis with sophisticated computer modeling and software that accurately simulates what will be happening with the architecture over time, using climate data specific to the location of the project. This is particularly valuable for passive house projects, where air movement is controlled and thermal assemblies are designed for extremely high performance.

Author: Sam Rodell

Sam has practiced as an award winning architect for forty years, and has also built many of his clients' projects.  He is licensed throughout most of the western USA and Canada, and is certified by the National Council of Architectural Registration Boards (NCARB) which expedites registration in other states and provinces. He was the first Certified Passive House Consultant architect in eastern Washington and northern Idaho.

Author: Maren Longhurst

Maren is a licensed architect particularly interested in high performance architecture and building science.   She holds a Masters in Architecture from Academy of Art University in San Francisco, and is a Certified Passive House Consultant, certified LEED (Leadership in Energy & Environment) professional, and a WELL Accredited Professional (a credential that signifies knowledge in health and wellness in the built environment and specialization in the WELL Building Standard). Maren is also on the Passive House Northwest board of directors.