By Planet Greenhouse | Published July 2026 | 12 min read
Most greenhouse guides tell you to "consider your budget" and move on. This one gives you the numbers.
Below is the full picture of what it takes to go from thinking about a glass greenhouse to standing inside one — what it costs, what foundation it needs, which glazing suits your climate, what your township will ask, and which accessories you'll actually use. Every figure here comes from greenhouses we've sold and delivered across the United States.
Quick answer: what does it take to buy a glass greenhouse?
A quality glass greenhouse costs $8,000 at the entry level, with most buyers spending $13,000 to $30,000. It needs an 8-inch concrete strip foundation anchored below your local frost line. Freight is included on every greenhouse we sell. Installation runs through a network of qualified installers, quoted by zip code. Most townships require a permit, and we can supply structural certification letters and an engineer referral to support that application.
Plan on three to six months from first conversation to finished build. The structure itself carries a 15-year limited warranty.
What this guide covers
- What a glass greenhouse actually costs
- What size greenhouse you need
- Glass, polycarbonate, or hybrid
- What foundation a glass greenhouse needs
- Where to put it
- Whether you need a permit
- Who assembles it
- Which accessories are worth buying
- Growing through winter
- Common questions
What does a glass greenhouse actually cost?
A quality glass greenhouse costs $8,000 at the entry level, and most buyers spend between $13,000 and $30,000. That covers the structure — powder-coated aluminum frame, 4mm tempered safety glass, doors, roof vents, louvered window, and gutters.
The sticker price is not the whole cost, and this is where most guides go quiet. Here is the honest breakdown:
| Line item | Cost |
|---|---|
| Greenhouse structure | $8,000 entry · $13,000–$30,000 typical |
| Freight shipping | Included — possible surcharge if flatbed and forklift are required |
| Foundation | Local masonry quote — varies with frost depth, site, and region |
| Installation | Quoted by zip code, or DIY |
| Permits | Township-dependent |
| Accessories | Most buyers add an exhaust fan, thermostat, and shelving |
| Warranty | 15-year limited, included |
On freight: a greenhouse ships as a heavy pallet of aluminum extrusions and a crate of tempered glass. Quoted separately, that is not a small number — and most retailers do quote it separately. We include it. The only exception is when your site needs a flatbed truck and forklift to unload, which we will tell you about before you order rather than after.
Two costs we will not invent a number for are foundation and installation. Both depend on your frost depth, your site, your access, and your local labor rates. A national average would be wrong for most of the people reading this. Send us your zip code and we will get you a real one.
What size greenhouse do you need?
Most buyers underestimate. The single most common regret we hear is not about price or glazing — it is that someone wishes they had gone one size larger.
Greenhouse space fills faster than expected. Potting benches, shelving, a heater, walkways, and the plants themselves consume floor area quickly. If you are choosing between two sizes and the budget allows, the larger one is almost always the right call.
| Model | Footprint | Suits |
|---|---|---|
| Royal Victorian VI23 | 7'9" × 10'2" | A focused growing space; smaller gardens |
| Royal Victorian VI34 | 10'2" × 15' | The most common choice — room for benches and walkways |
| Royal Victorian VI36 | 10'2" × 19'10" | Serious year-round growing |
| Royal Victorian VI46 | 12'7" × 19'10" | Wide enough for a center aisle with benches both sides |
| Cathedral | 15' × 19'10" | Heavy-duty portal frame construction |
| Royal Orangerie | 15'7" × 12'10" | Architectural presence; garden room use |
| Gigant | Custom to 20' × 60' | Pavilions, living space, event venues |
Also plan for what surrounds the greenhouse. Leave roughly 30 inches of clearance on all sides for ladders and glazing installation during the build, and for cleaning gutters afterward.
Should you choose glass, polycarbonate, or hybrid glazing?
Most guides frame this as glass versus polycarbonate. That binary is the wrong question, because the roof and the walls have different jobs.
Walls are about light transmission and how the structure looks from your kitchen window. Roofs are where heat gain, hail, and snow load actually happen. There is no rule saying both have to be the same material.
| Glazing | Strengths | Tradeoffs | Best for |
|---|---|---|---|
| 4mm tempered safety glass | Maximum light transmission; the clearest view; classic appearance; will not yellow or cloud with age | Heavier; less insulating than twin-wall polycarbonate; vulnerable to severe hail | Buyers who want the traditional glasshouse look and light |
| 10mm polycarbonate | Strong impact resistance; diffuses light so plants below are not scorched; better insulation | Less visually clear; can discolor over many years | Hail-prone regions, harsh sun, or colder climates |
| Hybrid | Tempered glass walls with a UV and heat-blocking polycarbonate roof — light and clarity where you see it, protection where the weather hits | Not every model offers it | Most buyers who want glass aesthetics without the summer heat problem |
Why hybrid solves the real problem: the roof takes the direct overhead sun in July, the hail in spring, and the snow in January. A polycarbonate roof handles all three better than glass. Meanwhile the walls — the part you look at and look through — stay tempered glass. You keep the greenhouse you wanted and remove glass's two genuine weaknesses.
One thing to know: tempered glass cannot be cut. It shatters. If you plan to mount an exhaust fan, order a lexan panel to replace one pane. Polycarbonate can be cut directly to fit the fan.
\What foundation does a glass greenhouse need?
We recommend an 8-inch concrete strip foundation with corner anchoring extending down to your local frost line. A full slab also works. Either way it must be completely level and sized to the greenhouse's exterior dimensions, which keeps rainwater from seeping under the frame.
This is the single most common question we get on the phone, and most buyers arrive with no idea what to specify. That is normal.
What drives foundation cost:
- Frost depth. A footing in Georgia and a footing in Minnesota are different pours. Frost line depth alone can double the concrete volume.
- Site conditions. Level ground is straightforward. Slope, poor drainage, rock, or tree roots are not.
- Access. Whether a concrete truck can reach the pad matters more than most people expect.
- Local masonry rates, which vary widely between markets.
Two things worth telling your contractor: Cathedral models require the portal frames and corner anchors to be embedded in concrete — that is not optional. And while small rectangular greenhouses can sometimes be anchored at the four corners alone, if you go that route, skip the lowered threshold option, because it will not be properly supported.
Get a quote from a trusted local masonry contractor who has walked your site. If you would rather not source one, we can connect you with an installer in our network who does qualified prep work.
Where should you put a greenhouse?
The best site is level, well-drained, sunny for most of the day, and sheltered from prevailing wind. Access to water and electricity matters more than people expect once the greenhouse is running.
Specifically, look for:
- Sun. Full-day exposure is ideal. Morning sun matters most in cold months, when you want the space warming early.
- Drainage. Avoid the low spot in the yard where water collects after rain.
- Wind shelter. A tree line or building on the windward side reduces heat loss in winter and stress on the structure in storms — but keep enough distance that you are not fighting shade or falling limbs.
- Utilities. Running water and power to a far corner of the property is a real cost. Factor it in before you fall in love with the view.
- Clearance. Roughly 30 inches around the perimeter for the build and for future maintenance.
Do you need a permit to build a greenhouse?
Often yes, and it depends entirely on your township. Requirements vary by municipality and there is no national rule we can point you to.
Call your local building department and ask about setback requirements, whether a permanent foundation triggers a permit, what snow and wind loads apply in your area, and whether an engineer's stamp is required.
What we can supply: a referral to our recommended engineer if your township requires one, and previous structural certification letters for reference. Those letters are reference material rather than site-specific engineering, but they often answer the first questions a building department asks.
Handle this before you pour concrete, not after.
Who assembles a glass greenhouse?
We do not install directly. We maintain a network of qualified installers across the United States, and we will get you a real quote once we have your zip code.
Finding someone competent to assemble a large glass greenhouse is a genuine gap in this market — most buyers discover it after the pallet is already in the driveway. Our network exists because that call kept happening.
If you are building it yourself:
- These are assemblable by a skilled DIYer. The manuals are thorough and plenty of our customers do it.
- Budget real time. This is a multi-weekend project, not an afternoon.
- Janssens greenhouses are engineered in metric. A metric or combination tape measure will save you a great deal of frustration.
- Hinged doors are the hardest part. They are significantly more difficult than sliding doors and may require a grinder. Many capable DIYers hire out this piece specifically.
- Assemble in dry, windless weather. Handling large panes of tempered glass in wind is dangerous.
Which greenhouse accessories are actually worth buying?
Most buyers add three or four items, and an exhaust fan is nearly always the first. A glass greenhouse traps heat — that is the entire point in February and the entire problem in July.
| Accessory | What it does | Worth it? |
|---|---|---|
| Exhaust fan | Pulls the hottest air out of the gable | Yes — the most common addition for a reason |
| Lexan panel | Replaces a glass pane so the fan can be mounted | Yes, if you are adding a fan to a glass model |
| Thermostat | Runs the fan automatically | Yes — turns ventilation into something you stop thinking about |
| Retractable roller shades | Shields plants from peak sun | Yes in hot climates or with sensitive plants |
| Slat shelving (2 or 5 slat) | 59" long, spans two glass sections, height adjustable | Yes — nearly everyone wants more surface |
| Narrow top shelf | Runs the length of the long wall (Victorian models) | Useful for seedlings and small pots |
| Seed tray | 20" wide, 4" planting depth, drainage bottom | Yes if propagation is a main use |
| Heater | Winter protection | Essential for year-round growing |
Order the long items with the greenhouse. The seed tray, narrow top shelf, and hinged doors all ship by freight truck because of their length. Adding them to the original order costs substantially less than ordering them later, when freight is charged on its own.
Ventilation setup that works: place the exhaust fan opposite the louvered window to create a cross breeze. For the strongest airflow, close the roof vents so air is forced through the louver rather than escaping straight up.
Can you grow through winter in a glass greenhouse?
Yes, and for most of our customers it is the entire reason they bought one. An unheated glass greenhouse extends your season by several weeks at each end. A heated one lets you grow year-round, overwinter tender plants, and keep citrus, figs, or tropicals alive in climates that would otherwise kill them.
What matters for winter performance:
- Heating. Size the heater to your volume and your coldest expected night, not the average.
- Glazing. Polycarbonate insulates better than glass. A hybrid roof helps here as well as in summer.
- Air circulation. Still, humid winter air invites fungal disease. Keep air moving even when it is cold.
- Foundation. Anchoring below the frost line is what prevents heave from racking the frame over successive winters. This is why we specify it.
Common questions
How long does a glass greenhouse last?
Decades, when it is properly built and anchored. Janssens greenhouses use powder-coated aluminum framing, which does not rot or rust, and carry a 15-year limited warranty. The foundation is usually what determines real-world lifespan — a structure anchored below the frost line will outlast one that was not.
Can tempered glass be cut to fit?
No. Tempered glass shatters when cut. If you need an opening for an exhaust fan, order a lexan panel to replace a pane, or choose polycarbonate glazing, which can be cut directly.
How long from order to finished greenhouse?
Plan on three to six months end to end. That includes the planning conversation, permitting, foundation work, manufacturing and freight from Belgium, and assembly. The foundation and permit steps are usually what set the pace, which is why we recommend starting them early.
Is a glass greenhouse worth it compared to a cheap kit?
Against a $600 hoop house, no glass greenhouse looks like a bargain. Against replacing that hoop house every few seasons, watching it fail in the first real windstorm, and losing the plants inside, the math changes. Our customers are not looking for cheap. They are looking for a structure that outlasts them and looks like it belongs on the property.
Do I need a permit?
Usually, though it depends on your township. Call your local building department before pouring concrete. We can provide structural certification letters and an engineer referral to support the application.
What foundation does a Janssens greenhouse need?
An 8-inch concrete strip foundation with corner anchoring extending below your local frost line. It must be completely level and sized to the greenhouse's exterior dimensions. Cathedral models additionally require portal frames and corner anchors embedded in concrete.
Get a real number for your site
Everything above except the greenhouse itself depends on where you live and what your yard looks like. We would rather give you an accurate figure than a national average that is wrong for your county.
Send us your zip code and we will put together the full picture — greenhouse, foundation guidance, an installation quote from our network, and what your township is likely to require. No obligation, and no pressure to buy anything today.
Most people who call us have no idea what foundation they need or what size makes sense. That is exactly what we are here for.
Request a quote · 307-271-8462
Planet Greenhouse sells Janssens of Belgium greenhouses, manufactured in Lier, Belgium and imported to North America by Exaco of Austin, Texas. We also carry Riga, Hoklartherm, and Alton cedar structures.