Outdoor sofas can indeed be used in a glassed-in belvedere without significant fading, but several factors must be considered to ensure longevity. While the glass provides some protection from direct rain and wind, UV rays can still penetrate, causing fabrics and materials to fade over time.

To minimize fading, opt for outdoor sofas made with sun-resistant fabrics like solution-dyed acrylic or polyester, which are designed to withstand prolonged sun exposure. Additionally, choosing furniture with UV-protective coatings or treated frames (such as powder-coated aluminum or teak) can further enhance durability.

Positioning also matters—placing sofas away from direct sunlight or using sheer curtains to diffuse harsh rays can help. Regular maintenance, such as cleaning with UV-protectant sprays, will also extend the sofa's vibrancy.

In summary, with the right materials and care, outdoor sofas can thrive in a glassed-in belvedere while retaining their color and quality for years.