Building Retrofit with Moisture-Related Problems

Enclosed swimming pools in winter climates have the potential for high indoor relative humidities and cold building materials. These elements can contribute to condensation and premature deterioration of building materials. Buildings can be designed to meet these challenges by determining the proper placement and type of vapor retarder in the walls and roof of the high humidity environment, and by using moisture resistant materials where surfaces are exposed to high humidities. Other buildings with the potential for high relative humidities include ice rinks and special purpose rooms in hospitals and laboratories.

Buildings with lower relative humidities in cold climates tend to be more forgiving because they have opportunities to dry out. Moisture due to rain or floods penetrating the building envelope tends to evaporate from low relative humidity buildings in the winter. Moisture due to indoor moisture migrating outwards during the winter tends to evaporate in the summer months. Buildings with high interior relative humidities throughout the year do not have these forgiving seasons, and must be carefully designed to prevent moisture problems.

Experts at CTLGroup performed an evaluation after moisture, thought to be roof leaks, was reported around some skylights at a recently constructed indoor swimming pool in a Chicago suburb.

Comparing reports of roof leaks to weather data indicated no correlation with precipitation, but a good correlation with low temperatures. A preliminary inspection revealed no indication of roofing deficiencies or water leakage around windows or skylights. It was evident that the reported leaks were related to building moisture problems rather than a roof leak. Exterior brick masonry exhibited excessive efflorescence in the area of the swimming pool, and water streaks were visible on the exterior walls below the eaves.

The evaluation included a visual inspection, Fourier transform infrared spectrometry (FTIR) analysis on water stains on the masonry walls, borescope inspection through roof and wall assemblies, measurements of interior relative humidities and temperatures, measurement of interior-exterior pressure differentials, and exploratory openings made through the roof assembly. Analyses were performed to evaluate condensation potential through the roof and wall assemblies under actual and design conditions. Condensation rates were calculated for each case.

Results of the evaluation indicated presence of condensed moisture as direct cause of the observed water stains, reported leaks and masonry efflorescence. The CTLGroup team developed recommended corrective actions for the client.