Condensation and Cladding Attachments
Manage moisture or face costly consequences
Condensation occurs if any surface is colder than the dewpoint temperature―the temperature where water in the air condenses into liquid.
In commercial building wall systems, condensation typically results
- from thermal bridging, when the colder exterior temperature bridges through to the warmer interior, or
- when a chilled interior bridges to a hot exterior climate.
Metal cladding attachment elements are highly conductive, allowing heat energy and air to bypass the thermal insulation and air-water barrier. Thermal bridging can significantly degrade the wall system’s insulating performance, leading to higher operating costs due to the heat loss.
The more moisture that’s present in the air infiltrating a wall system by thermal bridging, the more condensation occurs. If moisture accumulates as result of the condensation, it can negatively affect other materials inside the wall cavity. The condensation issues of moisture accumulation due to thermal bridging also further degrade the cavity insulation’s thermal resistance.
What’s the worst that can happen?
Moisture build-up can destroy or diminish the integrity of building components, and compromise the building’s structural performance. It can rot wood, corrode steel, crack masonry, and delaminate fiberglass and other composite materials. It can seep into finished interior spaces, causing physical damage as well as creating visual stains. When mold develops, these stains can be accompanied by an unpleasant odor.
Moisture-grown mold, mildew and other microorganisms can negatively affect indoor air quality and occupants’ health. The repercussions can be especially detrimental in health care facilities, senior living residences, daycares, k-12 schools and other environments where the occupants’ lungs are small, still developing or performing at a reduced capacity. Even among generally healthy people, increased exposure to mold is associated with asthma, allergies, headaches and respiratory discomfort.
Aside from the lasting costs to the affected individuals, health-related absences also are costly to employers in lost productivity. “Sick building syndrome” or “building related illness” are terms used to describe when occupants of the same space share similar health issues. If mold is discovered as the culprit, mitigation will be an expensive undertaking for the owner in terms of removal and renovation, as well as in lost revenue from leases and from possible legal costs.
How can this be prevented?
Understanding the cladding attachment’s thermal performance and making informed choices can significantly reduce thermal bridging and the associated condensation issues.
For example, Z-girts are still commonly used as cladding attachments, but they can degrade the R-value of the insulation by more than 50 percent. Today, there are numerous thermally efficient cladding attachments available to ensure energy-efficient, condensation-resistant building performance.
Online tools, such as “Thermal Envelope,” can be valuable resources for comparing the performance of wall cladding in a building envelope. Installation comparison exercises also can better inform decisions about the wall system’s optimal, total installed cost.
Remember to focus on long-term value rather than short-term purchase price when evaluating the true, total cost. Involve the wall system manufacturer and attachment suppliers early in the project’s development to ensure the best total value for the building owner and occupants.