One way to ensure your product sells well is to ensure that it meets a need that has yet to be fulfilled. It’s an approach that Bison Frames used when developing its Genesis vertical slider and as sales and growing awareness of what it has to offer prove, it’s more than paid off. Mark Tetley of Bison explains more. “The accepted wisdom in the industry is that listed buildings and properties in conservation zones are out of bounds for PVC-U windows. We always thought that was very unfair – both for us as an industry and for homeowners looking to.