Tell them not to waste their money. They don't work. I've cleaned roofs with the zinc strips. I even sold them as an add on to a few roof cleanings 6-7 years ago. The algae came back. Shingle sheild sells them as 3' strips in a box. If you read the directions, you are suppose to put them every 2' down the roof. Can you imagine how that would look. Sell them on a roof cleaning and a maintenance program.
Tell them not to waste their money. They don't work. I've cleaned roofs with the zinc strips. I even sold them as an add on to a few roof cleanings 6-7 years ago. The algae came back. Shingle sheild sells them as 3' strips in a box. If you read the directions, you are suppose to put them every 2' down the roof. Can you imagine how that would look. Sell them on a roof cleaning and a maintenance program.
I totally agree with Chris. Big waste of money and they really don't do anything to keep your Roof any Cleaner.