Effects of Climate Control on the Museum Building Envelope

Abstract

The museum building is sometimes called “the major artifact in the collection.” The building envelope serves as the boundary between the indoor conditions and the outdoor conditions. Any difference between indoor and outdoor temperature or humidity produces stress on the envelope, in the same way that air changes within the museum environment can stress a museum artifact. Although building envelopes are designed to resist stress, excessively tight indoor control can be harmful to the envelope. In a well-controlled environment, a balance is achieved between the stresses on the envelope and those on the artifacts.This paper presents the standard methods for analyzing the hygrothermal performance of a building assembly and describes the limitations of those methods. Next the paper presents a review of psychrometrics—the science of air-water interactions. The psychrometric chart is used as the base for introducing the effects that are missing from standard building performance analysis: moisture content of materials, air convection, and time-dependent effects. Practical matters presented include: setting upper and lower humidity limits in the exhibition space; temperature and moisture distributions in a space and in a climate control zone; the winter and summer performance of mechanical equipment; instrumentation; and building monitoring. Finally, guidelines for climate control that are aimed at maintaining the museum building envelope are presented.