Flad Architects

The Role of Basic Hygrothermal Wall AnalysisOne of the fundamental jobs of a building is to keep water out of unexpected places. The simplest example of this is the roof, which keeps rainwater out of interior spaces below. On earth, though, water is found almost everywhere. It's in materials, in the air, and in unwitting carriers called "living things" – people included. Most of the time the water generated from respiration or present in the air isn't a problem; however, if this airborne water vapor condenses in the wrong place it can create major issues, especially for building enclosures.

Modern buildings are enclosed by a series of material layers, each with a particular function – metal studs or masonry allow walls to stand up to wind and impacts; insulation keeps heat from traveling through exterior walls; and brick or exterior panels keep bulk water – rain, for example – from penetrating the wall. Often, one or more of these layers contains cellulose, the organic plant matter that is used to make paper and some types of insulation. Paper is frequently used as the face of gypsum sheathing, wall board, and insulation. As water vapor condenses on these surfaces, it creates ideal conditions for mold to thrive.

So, how do we stop the mold?Stop the condensation, or better yet, prevent condensation in the first place. Thankfully, there are a number of tools available to designers and architects to help predict whether condensation will be an issue. Some are proprietary and available by working with specialty consultants or product vendors. Others, like the German program WUFI, are publicly available (most for a fee). Before reaching for any of these, though, designers can use simple spreadsheet tools such as Microsoft Excel to identify potential problem areas utilizing the Glaser method.

Don't Sweat It

The Role of Basic Hygrothermal Wall AnalysisOne of the fundamental jobs of a building is to keep water out of unexpected places. The simplest example of this is the roof, which keeps rainwater out of interior spaces below. On earth, though, water is found almost everywhere. It's in materials, in the air, and in unwitting carriers called "living things" – people included. Most of the time the water generated from respiration or present in the air isn't a problem; however, if this airborne water vapor condenses in the wrong place it can create major issues, especially for building enclosures.

Modern buildings are enclosed by a series of material layers, each with a particular function – metal studs or masonry allow walls to stand up to wind and impacts; insulation keeps heat from traveling through exterior walls; and brick or exterior panels keep bulk water – rain, for example – from penetrating the wall. Often, one or more of these layers contains cellulose, the organic plant matter that is used to make paper and some types of insulation. Paper is frequently used as the face of gypsum sheathing, wall board, and insulation. As water vapor condenses on these surfaces, it creates ideal conditions for mold to thrive.

So, how do we stop the mold?Stop the condensation, or better yet, prevent condensation in the first place. Thankfully, there are a number of tools available to designers and architects to help predict whether condensation will be an issue. Some are proprietary and available by working with specialty consultants or product vendors. Others, like the German program WUFI, are publicly available (most for a fee). Before reaching for any of these, though, designers can use simple spreadsheet tools such as Microsoft Excel to identify potential problem areas utilizing the Glaser method.

Flad Architects

The fundamental aim of the Glaser method is to trace the dewpoint through different layers of a wall assembly, answering the question "what is the dewpoint on each of the layers?" Remember, the dewpoint is the temperature at which water will condense out of the air, so if the temperature of a surface is below the dew point, it will "sweat" like a cold beverage on a humid summer day. The calculation can be overwhelming on paper, but is relatively easy to set up in a spreadsheet. It provides a reliable means of identifying potential problem areas for further investigation.

Many researchers have identified shortcomings with the Glaser method. After all, it was designed to test walls in a single season (winter), for a single building type (homes), in a single region (central Europe). It was also developed in an era before it was common to carry a supercomputer in one's pocket, and it ignores a number of dynamic variables (for example, air movement at the wall faces, or changes in vapor drive at different temperatures). However, the principles of this method can be applied to any building material. As such, it still serves as a solid point of entry for designers (and building owners) who want a greater confidence in the building's ability to prevent the intrusion of environmental contaminants like mold and can provide a reliable gut-check on whether further investigation is needed.