Sweating chilled water pipes (CWP) can be a significant source of building dampness and mold. Lines supplying chilled water to air handling units are insulated to prevent surface condensation and conserve energy. Insufficient insulation, incomplete sealing during installation and damage during maintenance are common, allowing condensation to form on surfaces, eventually wetting the insulation and supporting mold growth. A protocol for assessing and remediating mold on CWP insulation and ensuring effective re-insulation, through effective quality control was developed in conjunction with a project for replacing failed CWP insulation in 15 schools. Cost-effective resolution of mold growth WP was demonstrated.

At a football stadium & convention center, in Houston, Texas, the original chilled water (CHW) pipe insulation systems required replacement due to extensive moisture intrusions. Although the CHW flowed continuously, the Air Handling Units were shut down when the building was not in use. This allowed the indoor environments to be exposed to Houston’s outdoor high temperatures and humidity during those times. Remediation required replacing the CHW pipe insulation with an insulation system of a totally different design without major pipe relocations and while the CHW circulated through the pipes being reinsulated.

Mechanical pipe insulation systems are installed on chilled water pipes that operate at below ambient temperatures inside buildings. Water vapor is drawn from the surrounding ambient air toward the pipes and the thermal conductivity of the pipe insulation systems is affected by ambient temperature and water vapor ingress. This talk provides an overview of the findings from two recent ASHRAE funded research projects on this topic. The speaker shows cases in which pipe insulation thermal conductivity increased with moisture ingress. This talk also illustrates the importance of including appropriate insulation thickness safety margins.

Mr. Hart will summarize the results of several hygrothermal analyses, using commercially available software, on simulated insulated chilled water pipe, held at a fixed temperature for 25 years in a Houston, Texas ambient environment. The pipe insulation modeled was a highly porous mineral fiber material with each of four different sheet-type vapor retarder jackets. These jackets had water vapor permeance values from a high of 0.134 perm to a low of 0.005 perm. The results show significant differences in predicted quantities of water vapor condensation and in subsequent increases in insulation thermal conductivity between each of the four insulation systems.