Synthetic underlay is much lighter than felt underlay; therefore, utilizing synthetic as an effective water barrier adds less weight to the roof than asphalt felt underlay.
The lightness of synthetic underlayment makes it easier and safer to install than asphalt felt.
Synthetic underlayment is much more tear-resistant when exposed to high winds and foot traffic than asphalt felt underlayment.
Since synthetics do not absorb moisture, they are resistant to fungal growth and are wrinkle-free.
Synthetic underlayments are ultraviolet (UV) resistant. Sunlight exposure degrades asphalt felt.
Synthetic underlayment maintains its integrity when exposed to cold weather, while asphalt felt wrinkles when wet and cracks when cold.
Synthetic underlayment rolls are 3.5-feet long and cover closer to 875-square-feet; therefore, synthetic underlayment installs faster than asphalt felt rolls that are 3-feet long and cover about 400-square-feet.
Unlike synthetic underlayment, asphalt-saturated felt roof underlayment contains volatile compounds. Over time, these compounds will dissipate, particularly when exposed to heat, which causes the underlayment to become more moisture-absorbent and fragile.