The answer to 'best underlayment' is using a high-quality synthetic underlayment. Synthetic underlayments are more durable, water-resistant, and breathable than traditional felt paper underlayments. They provide better protection against moisture, wind, and fire, and can last the lifetime of the roof. Common synthetic underlayment options include polyethylene, polypropylene, and rubberized asphalt products.
When choosing an underlayment, look for one that meets or exceeds industry standards for tear strength, water resistance, and UV exposure. Proper installation is also crucial, so be sure to follow the manufacturer's instructions carefully. For the best results, it's generally recommended to have a professional roofer install the underlayment and shingles.