Janssens | 20x15 ft Cathedral Victorian Glass Greenhouse Kit With 4mm Tempered Glass Glazing



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The 20x15 ft Janssens Cathedral Victorian Glass Greenhouse is a versatile, spacious, feature packed addition to any garden or backyard. The 20 by 15 foot floor size, tall sides and extended roof cupola section allow space for all of your plant growing needs, or use it as a hot tub cover or outdoor sunroom.

Price shown is for the baseline configuration mentioned below (see Features section).  Occasionally, we may have a few of this configuration available in the pipeline in various colors, which shortens the wait time.

Please call us at 888-648-5333 to schedule a free design session. You can specify the size,  the color, the number and type of windows, the number and opener types for roof vents, the door types and count, bench options, decorative spandrels, finials, roof crests, and more.

The attractive looks of the Cathedral Greenhouse are matched by superior strength of pre-welded aluminum framing and 4mm tempered glass construction. This choice of glass provides a high degree of safety and impressive insulation value.

The Janssens Cathedral Glass Greenhouse includes:

  • Four roof vents with automatic openers,
  • A louver window to help keep the interior at a comfortable temperature,
  • Two large hanging windows on the sides can also swing up for added ventilation,
  • A wide set of lockable swinging doors for easy access,
  • A single lockable sliding door make entry simple.

This is a premium, large size structure that can be used for multiple purposes and will add value to your home.

Please call us at 888-648-5333 to schedule a free design session. You can customize the size, the frame color, the number and type of windows, the number and opener types for roof vents, the door types and count, bench options, decorative spandrels, and more.

Take advantage of this beautiful greenhouse to create a unique area to enjoy. This special greenhouse is a custom order. 

  • House a Jacuzzi Tub and surround it with your favorite plants
  • An Inspiring Art/Hobby Studio
  • A Tea House
  • A Planetarium
  • An Entertainment Room
  • A Yoga/Exercise Room
  • A Mediation/Relaxation/Reading Sanctuary
  • A retreat to enjoy fresh air and sunlight

This greenhouse is NOT designed to be a build-it-yourself-kit.  It has to be mounted by experienced builders who are familiar with these products and their assembly! Due to the size of this greenhouse we recommend that you check your local building code for any required permits and view the foundation construction guide prior to ordering.

NOTE: The Cathedral Greenhouse is available by special order only. Please call (888) 648-5333 for ordering information. It is also recommended that you view the foundation construction instructions and easy assembly instructions prior to placing your order.

  • 298 sq ft floor space
  • 1 double set of hinged doors with closers
  • 1 sliding door
  • 2 top hanging side windows
  • 1 louvre window
  • 4 roof windows with automatic openers
  • 4mm tempered glass
  • 2 heavy duty aluminum reinforcement supports from front to back - 2.3" W x 5.2" D.
  • 10'2" L x 5'4" W cupola with pre-welded frame (horizontal part).
  • Greenhouse is 15' W x 19'11" L x 12'2" H, side walls are 6'8" H.
  • Main Dimensions: 19' 10" W x 15' L x 12' 2" H
  • Second level roof nook dimensions: 5' 4" W x 10' 2" L
  • Floor space: 298 sq. ft.
  • First gutter height: 6' 8"
  • First ridge height: 9' 1"
  • Second gutter height: 10' 9"
  • Second ridge height: 12' 2"
  • T.U.V. & GS tested and approved, which is similar to UL testing & listing

15 Year Limited Warranty

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Ask a Question
  • Do you have green house size 20’x50’

    Yes, we are able to custom configure some of the Janssens greenhouses up to 20' x 60'. 
    Please call us as 888-648-5333 to discuss your project.

    For the Cathedral model, the largest we can configure is 15' x 30'.

  • Do you have the capacity to manufacture a 2000 sq ft observatory?

    An astronomical observatory?  Only to the extent that a greenhouse (or geodesic dome) could be used for that purpose.  Janssens in particular has the ability to highly customize their buildings, however it would likely be something to explore interactively a bit to see if there are particular requirements that can be accomodated.