The Janssens Greenhouse Roof Vent can be added to any Royal Victorian or Cathedral Greenhouse at the time of order. They come in black or green. Most Royal Victorian and Cathedral Greenhouse models already include at least one roof vent. You can add as many roof vents as you want to your greenhouse with the caveat that you cannot put the vents adjacent to each other - so 'every other panel' would be the most you can add. Optional auto-openers and fly screens are available. KEY FEATURES Improves Greenhouse Ventilation Helps release excess heat and humidity while promoting healthy air circulation throughout the greenhouse. Designed for Janssens Greenhouses Built using the same aluminum profiles and glazing system as Janssens greenhouse structures for a factory-integrated appearance. Manual or Automatic Operation Can be operated manually or paired with an optional automatic opener for hands-free temperature-responsive ventilation. Supports Year-Round Growing Proper ventilation is essential for managing temperature, humidity, and plant health across all seasons. Compatible Fly Screen Available Add an optional fly screen to help keep insects out while maintaining airflow through the roof vent. Made in Belgium Manufactured by Janssens, one of Europe's most respected greenhouse manufacturers. OPTIONAL ACCESSORIES Color: Black or Green Custom colors can be ordered (e.g. when ordering a greenhouse in a custom color), call us at 888-648-5333 Auto-opener (heat operated) available here Fly Screen available here WARRANTY 15 Year Limited Warranty MANUFACTURER INFO AND UNIQUE SELLING POSITION Janssens Greenhouses has been manufacturing premium greenhouse structures and accessories in Belgium for decades. Known for exceptional craftsmanship, heavy-duty aluminum construction, and refined European design, Janssens products are trusted by serious gardeners, educators, and greenhouse enthusiasts throughout North America. The Janssens Roof Vent uses the same factory-engineered components found in Janssens greenhouse kits, ensuring seamless integration, reliable operation, and long-term durability. Unlike generic aftermarket vents, it is specifically designed to match the appearance, glazing, and structural performance of your Janssens greenhouse. FREQUENTLY ASKED QUESTIONS Why should I add additional roof vents to my greenhouse? Additional roof vents improve airflow, help reduce excess heat and humidity, and create more uniform growing conditions throughout the greenhouse. Do I need electricity for the automatic roof vent opener? No. Janssens automatic vent openers use a heat-activated paraffin cylinder and require no electricity, batteries, or wiring. How many roof vents should my greenhouse have? Larger greenhouses typically benefit from additional roof vents. Proper ventilation should generally equal 15% to 20% of the greenhouse floor area when combined with side ventilation. Can roof vents be installed next to each other? No. Janssens recommends spacing roof vents apart. In most configurations, vents should be installed in alternating roof panels rather than adjacent panels. Is a fly screen worth adding? Yes. A fly screen allows you to maintain ventilation while helping reduce the number of insects entering through the roof vent.