Janssens Cathedral Victorian Greenhouse 15×20


  • 4mm Temp Tempered Glass
  •  1x Set of Hinged & 1x Single Sliding Doors
  • Versatile Door placement
  • Taller Side walls = Greater head room
  • Floor Space: 298 sq.ft.
Black Janssens Cathedral Victorian Greenhouse 15ft x 20ft, empty, view from the side
Janssens Cathedral Victorian Greenhouse 15×20

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This glass greenhouse kit is the perfect choice for people who want something sophisticated in their backyards. The Cathedral from Janssens is a large Victorian greenhouse with a cupola. It can serve multiple purposes besides gardening, like a social gathering spot for dinner parties, sunroom, or pool cover.

The Janssens Cathedral Victorian Greenhouse has a sidewall height of 6.7′, which allows for great headroom everywhere. Towards the middle, you’ll get to enjoy 9′ height and a cupola that adds another 3′. This brings it to a total height of 12′! It certainly is our tallest greenhouse that offers the most headroom.

Besides that, the Cathedral Glass Greenhouse has 298 sq.ft. of floor space. It will give you plenty of room for growing the plants you want while not having to give up a sitting arrangement. You can have it both with this sturdy greenhouse structure.

The Janssens Cathedral Victorian Greenhouse comes with 4mm tempered glass. All glass panes are secured with heavy-duty rubber seals for better insulation all the way around – others use only metal clips or flimsy thin rubber strips.

If you want a greenhouse not just for gardening, but for social events or relaxation, as well as to add charm into your garden design, the Cathedral is the way to go!

Janssens – 75 Years of Experience

Janssens is a Belgian manufacturing company that specializes in high-end greenhouses, orangeries, and more. They are market leaders in Europe and in the USA. Their elegant glass greenhouses stand out because of their high-quality design and innovation.

Product Details

  • Large Victorian greenhouse with a cupola: perfect choice for people who want a sophisticated greenhouse in their backyard that also functions as a gathering spot
  • Frame material: Thick, strong aluminum frame
  • Frame finish is applied electrostatically for a thicker application and better coverage
  • Sidewall material/thickness: 4mm tempered glass
  • Great insulation: Tightly fitted design with rubber seals between frame and glazing, as well as sealant around windows
  • Door: 1x set of hinged double doors and 1x single sliding door (28″ x 72″) for multiple access points
  • Windows: 4x roof vents with spindle openers, 2x top-hanging side windows and 1x Louver window (28.5″ x 39″) for more ventilation and a better temperature control
  • Decorative roof ridge adds a touch of English sophistication
  • Included in the Janssens Cathedral Victorian Greenhouse Kit:
    • Frame, glazing, seals
    • 2x heavy-duty aluminum reinforcement supports
    • 3in high foundation frame
    • 4x roof windows with spindle openers (can order automatic non-electric)
    • 2x top-hanging side windows
    • 1x Louver window
    • 1x hinged double door, 1x single sliding door
    • Gutters with downspouts
    • Roof ridge decor
    • Assembly guide (also available here)
  • Rainwater gutter system: Yes
  • Expandable: No
  • Frame color:
    • Anthracite (Dark Grey) or Dark Green
    • Special order: Black and Bronze
  • Sidewall height: 6’8″
  • Peak height (exterior): 12’2″
  • First ridge height (where the cupola starts): 9’1″
  • Second gutter height: 10’9″
  • Floor space: 298 sq. ft.
  • Dimensions: 19’10” wide x 15′ long x 12’2″ high
  • Cupola dimensions: 5’4″ wide x 10’2″ long
  • BEFORE ORDERING: Check your local building code for any required permits because of the large size and foundation requirement!
  • Assembly time: Plan for a full weekend and get some helpers. You also need to plan additional time (prior to assembly) to build the footer or slab.
  • Warranty: 15 years limited
  • Made in Belgium
  • Shipping information: This product is delivered via LTL which is curbside delivery only. The driver will be using a pallet jack and liftgate to slide the crate off and will need help from the customer with the unloading of the framing boxes. We recommend having a couple of people there for the delivery.
  • Imported by Exaco Trading: We are a proud dealer for Exaco because they offer high-quality products with excellent customer service to help you with any post-purchase problems (if they occur).


General questions

Are there more customizations available?

If our selection isn’t quite what you want, you could get a custom Janssens greenhouse. Keep in mind the wait time will be longer (around 6 months). Sometimes it’s worth waiting if you can get exactly what you want. You can use Janssens’ configurator tool here! This way you can show us exactly what you want and we can get a quote for you.

Does it need a concrete foundation?

All Janssens greenhouses require proper footing because of the included foundation frame. We don’t recommend complete concrete slabs because they hold a lot of heat in the summer and a lot of cold in the winter. A glass greenhouse already heats up and cools down very easily. A footer filled with gravel, dirt, or pea rock in the middle is a better option. You have to cement the foundation into the footer for the perfect stability. Do not set concrete in the corners until the entire greenhouse frame is complete, level, and square! Please, have a look at the manual or this assembly video for the Royal Victorians. They illustrate how it’s done correctly.

Can I put the Royal Victorians on a stem wall?

Yes, you can purchase a drop door kit so that you can install the greenhouse on a 10-40” high stem wall. Please note, the kit does not include the glass that goes on top of the door. You can purchase this piece locally to suit your desired height.

Is it possible/wise to remove the rain gutters, say during the winter months?

No, the gutters are part of the aluminum extrusion.

Should we choose glass or Polycarbonate?

The choice between glass and Polycarbonate is an important one because they will serve different purposes. To keep it short: Glass is purely for aesthetics and Polycarbonate for functionality. You’ll have more protection from the weather and a better growing environment with Polycarbonate. It doesn’t look as nice as glass, though. Benefits & disadvantages of glass:

  • Great aesthetics
  • Fragile, may break
  • Panes do not fade or scratch easily
  • Allows most light, doesn’t break light (not a good thing in hot climates)
  • Less insulating
  • Heavy panels are difficult to handle
  • Easier and less expensive to find a replacement if needed
  • Harder to keep clean/clear (hard water, they will fog with humid climate inside the greenhouse)

Benefits & disadvantages of Polycarbonate:

  • Less visually pleasing
  • Sturdy, less likely to break
  • Panes may scratch and fade a little
  • Light breaks (no hot spots)
  • More insulating
  • Lighter panels are easier to handle
  • May take longer to replace
  • More expensive to replace

Glass has historically been used for greenhouses and has the best aesthetic appeal. It also lets in the most light without breaking it. The panes do not fade over time and are easy to replace. However, the panes can be heavier to work with, may break, have less insulation, and require more maintenance to keep clean. Advances over the years have made Polycarbonate an additional option worth considering. Polycarbonate has better light diffusion, is more resistant to changes in weather, and resists cracking. It is not as beautiful as glass, scratches more easily, and can be expensive to replace (in the case of breakage). For more details, read our article to help you with this choice.

What is the difference between a Royal Victorian and Junior Victorian greenhouse?

Junior Victorians are overall shorter and come in smaller sizes. When you compare the dimensions of the J-VIC 23 and VI 23, you’ll see that the center height is shorter. Also, the shoulder is significantly lower 5ft 2in on the J-VIC 23, versus 6ft 7in on the VI 23.

What is the difference between a Royal and Retro Victorian greenhouse?

The Royal Victorians have complete glass panels. The Retro Victorian utilizes narrower 14″ vertical panels of 4mm tempered glass with decorative non-glass panels for the lower sections. This creates a totally different look and might be an advantage in some weather situations.

What is the difference between the Junior Victorian Orangerie and Royal Victorian Orangerie?

These two orangeries look very similar but they are not identical. In case you are unsure which one to pick, we want to make it easier for you:

  Junior Victorian Orangerie Royal Victorian Orangerie
Peak height 8ft 2in 9ft
Shoulder height 5ft 2in 6ft 7in
Size 10ft 3in x 13ft 12ft 10in x 15ft 6in
Glazing Glass Glass or Polycarbonate
Door Single sliding Double sliding
Roof vents 2x 3x
Louver vents None 2x

The most significant differences in these two models are size and features. The Junior Victorian Orangerie is smaller overall than the Royal Victorian Orangerie. The Junior Victorian Orangerie has a shorter peak and shorter shoulder height than the Royal Victorian Orangerie. The Junior Victorian Orangerie is also shorter in length than the Royal Victorian Orangerie, with a smaller overall growing area and footprint. The Royal Victorian Orangerie has more features such as the choice of Glass or Polycarbonate, and more roof/Louver vents. If you would prefer the larger Orangerie now, click here to look at the product.

What is TUV & GS testing?

Products bearing the GS mark have been subjected to rigorous testing and evaluation. TUV & GS is German testing similar to UL Independent Testing and Certification in the United States. It is voluntary testing and certification that means a sampling of the product has been tested for safety and found to meet the minimum requirements of the German Equipment and Product Safety Act.

Accessories and add-ons

What heater would you recommend?

This highly depends on the size of the greenhouse. We offer some heaters here and guide you through picking the right heater here.

Do you sell an extra sliding door?

The Janssens Royal Victorian Single Sliding Door can be added at the back or side of your greenhouse. This way you can create two entrances. You can find the product here.

Janssens VI 34

Does the VI 34 come with a hinged double door?

No, it has a single sliding door. You can order a hinged double door if you desire one. Call or email for pricing.

Janssens VI 46

Is VI 46 a kit with instructions that a reasonably skilled craftsman and another person can assemble?

You can have a look at the manual and resources here and judge for yourself. If you feel it’s too complicated or you don’t have anyone who can help you, we recommend professional installation. You can hire a local contractor for the job. Installation can also be discussed with Exaco (the importer), especially if you are in Texas. You can reach them at (512) 407-8500. You should use Ext 701 to talk to Claudia and she can get the prices.

T-Shaped Orangeries

Where can I find a pdf of the assembly instructions for the Royal Victorian Orangerie?

You can find the assembly instructions (including the foundation information) on our manuals page.

Is the EOS Junior T Orangerie 10 ft front to back and 13 feet left to right as you stand at the front entry?

From the door to the back is 3189mm, which is roughly 10.46ft and the 13ft is indeed left to right as you stand at the front entry. Check Page 9 of the manual for more details.


Where does this ship from?

Austin, Texas

Do you deliver to the house?

This product is delivered via LTL which is curbside delivery only. You will need to work with the driver to unload the contents of the crate, leaving the crate on the truck. The exception would be if you have a forklift or tractor with long forks available, which can be used with the liftgate to lower the entire crate to the ground. We recommend having a couple of people there for the delivery. The VI 36 and VI 46 are particularly heavy.

How long does it typically take for the shipment to arrive?

It usually takes about 2 weeks for your order to arrive. This unit ships from Texas. It takes 1-2 business days to package and then it ships to the shipping facility located nearest to you. The shipper then makes contact to schedule a delivery. Due to the high demand during this pandemic, we are running low on products, and shipping companies take longer than usual. Please, keep this in mind when ordering. We will send you a follow-up email if there is a longer waiting time for your order.