"Synthetic" valley flashing

My brother-in-law is replacing his shingles and has had a couple of quotes that recommend a “synthetic” valley flashing material in place of metal. It is apparently used in the USA but new to Canada.

Does anyone have any experience with this product? (I don’t have a brand name) I believe it is used inconjunction with ice and water shield.

My questions would be:

Longevity vs. metal flashing
Tolerance of UV rays
Tear resistance
Permeability

Thanks in advance.

Valley materials depend entirely upon and vary with the type of roof covering being applied.

For asphalt based shingles, the 2003 International Resdiential Code allows two plys of mineral surface rolled roofing materials that meet ASTM D 249 to be used for open valleys.

For closed valleys, 1 ply of a smooth roll roofing material compying with ASTM D 224 Type I or Type II can be used, or ‘specialty underlayments’ complying with ASTM D 1970 can be used. Most Ice and Water shields meet this standard for ‘specialty underlayments.’

The 2006 International Resdiential Code requires material complying with ASTM D 3909 or ASTM D 6380 Class M for asphalt shingles with open valleys. Closed valleys can have lining complying with ASTM Class S Type II, Class M Type II, or ASTM D 3909. The ASTM D 1970 can also be used for specialty underlayment.

You would need to check Canadian Code and referenced Canadian standards to assure that any valley material that was being installed complied with Canadian standards regardless of where the material was made.

Could they be talking about rolled roofing if so bad choice .
I would stay with metal many installations I have seen the metal has been on for 3 sets of shingles .
Rolled roofing seldom lasts one set even when doubled layered.
Roy Cooke

Ice Shield