Mold growth in building mechanical systems (e.g., HVAC, plumbing, and pumps) is an emerging concern, particularly for aging buildings where moisture, poor ventilation, and material degradation are common. These conditions may reduce insulation performance and pose health risks to the workforce and building occupants. Despite these concerns, mold issues in mechanical insulation remain understudied and often overlooked in built environments and industry practices. To address this, a survey was conducted among mechanical insulators with varying levels of experience across the U.S. and Canada. This paper specifically analyzes the survey results related to mold issues encountered by mechanical insulators when working on mechanical systems in buildings. Based on 369 completed survey responses by heat and frost insulators in the U.S. and Canada, the findings indicate that mold is a widespread issue in building mechanical systems, with around 50% encountering it “very often” and “often,” particularly in confined spaces with limited-access areas. The survey results also highlight that mold is mostly found in insulation materials and is more dominant in aging mechanical systems. The most frequently reported challenges of mold issues were health risks (72%) and insulation degradation (67%). These results emphasize the need for mold-resistant materials, improved installation practices, and better maintenance of buildings mechanical systems. This study also explores how regional climate conditions influence mold issues within the built environments where mechanical insulators work. These insights can help improve safety guidelines, promote the use of more effective insulation materials, and inform policies that protect the health and efficiency of the built environment.