Based on the recurring issue of blistering paint on the bedroom walls near the windows, it is important to address the root cause to prevent further occurrences. Given that the painter used latex paint and fans for drying in the past, it is evident that moisture may be seeping through the walls, causing the paint to blister. To effectively combat this issue, using a shellac-based primer before repainting is recommended to create a protective barrier against moisture infiltration. Shellac is known for its excellent sealing properties and can help prevent water damage to the walls.

Moreover, opting for an oil-based paint over latex paint for the next application may also provide better moisture resistance and durability, especially in areas prone to moisture exposure such as near windows. Oil-based paints form a tougher and more impermeable finish, making them less susceptible to blistering caused by moisture.

In addition to using a shellac-based primer and oil-based paint, it is crucial to ensure proper ventilation in the room to prevent moisture buildup. Addressing any underlying issues such as leaks or condensation near the windows is also essential to prevent future paint blistering. Properly preparing the surface by cleaning and sanding it before repainting is key to achieving a smooth and long-lasting finish.

Addressing underlying moisture issues are crucial steps to prevent recurring problems. Find out where the moisture is coming from; roof leaking, gutters, stucco needing sealing or simply caulking the exterior window.