The insulated polycarbonate glazing helps retain heat better than thin single-layer coverings

1 roof window with spindle opener

outdoor activities and household items

professional assembly is strongly recommended for safety and performance

High impact polymer support arms are lightweight

Alton | Thermofor Roof Vent Opener Piston Replacement Palram - Canopia Carport The insulated polycarbonate glazing helpsThe Thermofor Long Piston Replacement is a direct replacement cylinder designed for Thermofor automatic roof vent openers used in Alton greenhouses. If your current opener is no longer responding properly to temperature changes, replacing the piston is a simple way to restore reliable, automatic ventilation. This heat sensitive cylinder contains a wax core that expands as temperatures rise and contracts as they cool, driving the vent to open and close