The best solution for rain-induced window water seepage involves a combination of waterproof window flashing, sealant application, and drainage system optimization. Flashing directs rainwater away from window frames and walls, while sealants fill gaps to prevent water infiltration. Proper drainage systems, such as French drains or downspouts, ensure excess water is channeled away from the foundation. These solutions are effective because they address both the source and pathways of water entry.

Waterproof window flashing, typically made of metal or polymer, is critical as it creates a barrier along the roofline and window edges. Studies by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) show that 70% of rainwater seepage through windows occurs due to improper flashing installation. Sealant application, including polyurethane or silicone products, bridges microscopic gaps in window frames and masonry, reducing water entry by up to 80% according to the National Association of Home Builders (NAHB). Drainage system optimization is equally vital; a 2022 study in the Journal of Building Engineering found that homes with optimized drainage systems experienced 50% fewer seepage incidents compared to those without. The EPA also notes that 90% of water leaks in residential buildings stem from poor installation or missing components, reinforcing the need for comprehensive waterproofing. Together, these measures create a multi-layer defense against rain-induced seepage, ensuring structural integrity and energy efficiency.