Cut Or Closed Valley’s Is The Question
Cut or closed valley’s: Many roofing contractors are making a big mistake by offering copper valleys as an architectural upgrade in performance and appearance to a new roof. Any contractor offering this does not know what he is doing. Copper and aluminum are not compatible metals. If copper valleys are used ALL other metals MUST be copper too. Drip edge, nails, gutters and downspouts. Water draining from a copper valley WILL corrode the drip edge and the aluminum gutters as well as the roofing nails. In addition, as copper valleys age they can stain the sidewall of the house, wood, brick and stone. Copper is the alpha of metals and is just one ingredient used in batteries because of its aggressive nature toward other metals.
Additionally, most copper valleys are formed with 16 OZ copper. This is a very thin metal compared to a shingle valley and is susceptible to corrosion due to acid rain, salt air and other non-compatible metals surrounding it.
Copper looks nice initially, but once it has aged it is greenish in color and not very noticeable and offers no additional performance. Using the roof shingles in the valleys will last as long as the roof itself. In a perfect setting Copper valleys have a lifespan about half of what todays shingles have. It really does not make sense to apply 50 year shingles and have the copper valleys deteriorate in half that time.
Please see: Galvanic corrosion in Wikipedia.
Once a copper valley corrodes the entire roof surrounding the valley will need to be removed to make repairs and install new shingles.