Kalwall is much more expensive because it's a more complex sandwich of materials and better insulated. You can get polycarb with low-e coatings and similar, and it's used in place of glass. It's very durable and will last decades. I have it on some projects that are 10 years old and it looks no different than the day it was installed. It doesn't yellow. It's a high quality material. If you look around you'll see it used for canopies, greenhouses, in malls, all over the place.

Hi would you please provide the exact product that you used for the deck roof? I used visible similar from Polygal (Polycoolite) but am having aging issues at the ends.

Hi - I believe we used a Macrolux brand approximately 1" thick multi-wall panel on this project. I have also used Polygal brand and Palram brands for the same kinds of projects.

Did you use the products with channels? Although I adhered to the manufacturer's installation guide - the edges (sealed with their strip) retained moisture and turned black.

Hi, sorry for the delay, we were camping. Yes, we used the multi-wall polycarbonate panels with the channels. It's true that you have to seal the edges well so that they don't collect dirt and turn black. Polygal has some of the best breathable tapes for closing the panel edges, made for this purpose. I used their edge tapes on a kitchen skylight back in 2006 and it never got dirty or turned black.