InfraMation 2004 Proceedings

ITC 104 A 2004-07-27

Infrared for Detection of Exterior Wall Moisture and Delamination:

A Case Study and Comparison to FEA Predictions

Jack M. Kleinfeld

Kleinfeld Technical Services, Inc.

ABSTRACT

An 80-year-old building, stucco over terra cotta, was surveyed for moisture from the exterior. Solar loading

was used to detect suspect areas. The results and basis of the IR are discussed. Physical probing is still in

progress, but some results are available. A comparison of the results to heat transfer simulation of the system

using FEA is also presented.

Keywords:

building thermography, moisture, delamination, heat transfer analysis, FEA, prediction, simulation

BACKGROUND

Kleinfeld Technical Services, Inc. was retained to provide a survey of the exterior of a building that had a

history of water problems in the walls. The survey was carried out in August. The building is located in the

Greater New York metropolitan area. It is approximately 80 years old, of stucco over terra cotta construction.

It is sufficiently isolated from neighboring buildings and other obstructions that nearly all walls receive direct

sun, at least in the summer. Solar loading was therefore used to drive the transients necessary to detect

moisture in the exterior walls. A series of scans of the outside was made over two testing days, covering a

time period from before sunrise through to early evening. Areas were scanned over the day, but not all areas

were scanned through the entire day. Weather on the two testing days was similar, with fairly clear skies, low

wind, and moderate air temperatures in the 70s to 80s.

A selection of images from one part of the building is presented along with some sample images from other

areas of the building. Findings included areas suspect for moisture and some areas suspect for delamination.

Additionally, clear evidence of filled-in windows, of which the owners were not aware, was found.

THERMAL BEHAVIOR OF WALLS

Surface thermal anomalies will be caused by structural and moisture conditions. In warm season conditions,

the exterior wall can be expected to be warmer than the interior. The following discussion is based on that

scenario.

Over a daily cycle of solar heating and air temperature-driven heating during the day and convective and

radiational cooling at night, the surface of the facade will respond in a manner indicative of and caused by its

condition and underlying materials. During solar exposure, starting from a cool nighttime state, areas that are

thermally better connected to the interior, that is, not well insulated, will warm more slowly. Similarly, those

areas with higher thermal mass, such as trapped water, will also warm more slowly. Areas that are not well

connected, such as those over disbonds or delaminations, will be unable to dissipate the applied heat as

readily and will warm more quickly and to a greater degree than the "normal" areas. The reverse behavior will

be observed during a cooling phase: wet areas or areas that draw more readily from the interior will stay

warmer, and disbonded areas will cool more rapidly.

The wet areas and the poorly insulated areas will tend to behave similarly. The ends of interior walls and of

floors are clear examples of the poorly insulated areas. It is necessary to make some judgments of areas that

are suspect solely on their thermal behavior: whether the indicators are structurally driven; i.e., caused by

walls, floors, penetration headers, etc.; or if there is evidence of moisture in the walls. Often the location and

comparison to similar locations should suffice. Information about the construction of the building, if available,