Dynamic Exterior Wall Systems for Solid Masonry Walls in Humidified Buildings

April 29, 2012

The challenges of “modernizing” solid masonry buildings are fairly well understood for typical buildings, but less so for humidified buildings, especially those in cold climates. The conversion of existing, often historically-significant buildings into climate controlled museum spaces is a fairly common theme in renovation projects. Unfortunately, failures in these types of buildings due to inappropriate treatment of the exterior walls is also common, and can have severe consequences for the operation of the building as well as its long-term durability. While “bare” masonry walls may be sufficient for non-humidified spaces such as offices and residential buildings, additional measures are necessary to control both heat and moisture migration through masonry walls in humidified buildings. In museum spaces, the treatment of exterior walls must also take into account their use as hanging walls for artwork, displays and other exhibits. Without adequate thermal and moisture control, wall hangings may experience significant localized temperature and moisture gradients even though the ambient interior conditions are held stable. From a preservation standpoint, it is these gradients, rather than specific temperature and relative humidity settings, that contribute to degradation of artwork and artifacts. This paper discusses the unique challenges of renovating masonry walls for humidified buildings, including considerations for controlling condensation and preventing fluctuating conditions on the wall surface, without leading to accelerated freeze-thaw damage or deterioration in the existing masonry. Specialized “dynamic wall systems” that couple the building enclosure with the mechanical system as a means of thermal and moisture control will be discussed, and practical examples of the implementation of these systems will be presented.

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