Weeks of heavy rain and cold weather across Morocco have led to a surge in mold spreading inside homes. Beyond damaging walls, indoor mold poses health risks, making proper daily ventilation essential to prevent its return. DR ‹ › With rainy weather dominating Morocco over the past few weeks, many have reported mold spreading across their houses, walls and ceilings. Many have taken to social media to share videos of dark mold patches spreading across bedrooms and living rooms, with homeowners seeking advice on how to remove them. But beyond the aesthetic damage, a more pressing question remains: why is mold spreading so rapidly this winter, and what does it mean for our health? To understand the phenomenon, the first step is identifying the type of mold and its source. According to Casablanca-based architect Mehdi Besri, the color of the mold can offer important clues. Black or Green? When mold appears black, Besri explains, it is usually linked to a direct and continuous source of moisture. «It is most often connected to a water leak or water infiltration», he told Yabiladi. In practical terms, this generally points to one of two structural issues. «Either there is a failure in waterproofing, for example, a balcony or roof that was not properly treated with a tar-based or bituminous waterproofing layer, or there may be a leak in the plumbing pipes within the building's service duct». In such cases, simply cleaning the stain will not solve the problem. Besri advises homeowners to hire a qualified plumber or professional to identify the exact source of the leak and carry out the necessary repairs, which may include fixing pipes, rebuilding damaged sections, or redoing the waterproofing. Indoor Air Pollution However, not all mold is caused by structural leaks. When the patches appear green, the problem is more often linked to ventilation. «It is more likely caused by poor air circulation», Besri said. During rainy and cold weather, windows are opened less frequently. As a result, indoor air remains humid. In other words, even without a leak, moisture trapped inside the home can be enough to trigger mold growth. Beyond structural explanations, indoor mold should not be underestimated. Dr. Tayeb Hamdi, physician and researcher in health policy and systems, describes «'ghmoulia', the Darija term for indoor mold, as a type of fungal growth caused by humidity». According to Hamdi, indoor mold should be viewed as a form of air pollution, and in some cases, it can be more harmful than pollution outside the home. Exposure to mold can cause irritation to the eyes, nose, throat, trachea, and ears. It can trigger allergies, affect breathing, and lead to skin problems, he said. In more serious cases, prolonged exposure may allow fungal particles to affect the lungs and potentially weaken the immune system. «Humidity inside our homes can be like a hidden enemy», he warned. Ventilate smart not hard The good news, however, is that prevention is often simple. Both experts agree that proper ventilation is essential. Instead of leaving a small window slightly open for hours, which is largely ineffective, Hamdi recommends opening two windows opposite each other for about 10 minutes, twice a day. This creates cross-ventilation, allowing humidity and indoor pollutants to exit quickly without cooling the walls excessively in winter. «In a two-story house, you can open one window downstairs and another upstairs», he added, describing what is known as vertical ventilation, which encourages natural air circulation. He also advises avoiding excessive indoor plants and never drying clothes inside the house, as both practices significantly increase humidity levels. After showering, residents should either use the bathroom exhaust fan or open a window to release trapped moisture.
