The best year-round greenhouse in Canada is the Outsunny 6′ x 10′ x 6.6′ Polycarbonate Greenhouse, priced at $549.99, because its rigid panels, galvanized base and two roof vents let it stay up through every season. Gardeners who need more room can choose the 6′ x 12′ model, while the 6′ x 4′ Walk-In suits small yards.
Our Top Picks at a Glance
- Best overall for year-round use: 6′ x 10′ Polycarbonate Greenhouse, with the highest wind rating on this list.
- Best for large gardens: 6′ x 12′ Polycarbonate Greenhouse, with the most growing space.
- Best for heat retention: 6′ x 8′ Polycarbonate Greenhouse, with twin-wall panels.
- Best compact pick: 6′ x 6′ Polycarbonate Greenhouse, small enough to heat easily in winter.
- Best for small yards: 6′ x 4′ Walk-In Polycarbonate Greenhouse, the lowest-priced pick.
How We Picked These Year-Round Greenhouses
A greenhouse used in every season needs rigid panels, a solid base and good airflow, since even bright winter days can overheat an enclosed space. Extension specialists recommend roof vents and side vents that each equal about 15% to 20% of the floor area.[1] We chose Outsunny polycarbonate models with aluminum frames, built-in bases and roof vents, and compared each on size, panel type, ventilation, anchoring and price.
Quick Comparison: Best Year-Round Greenhouses
| No. | Greenhouse | Price | Size | Panels | Best For |
| 1 | 6′ x 10′ x 6.6′ Polycarbonate Greenhouse | $549.99 | 63.7 sq ft | 4mm polycarbonate | All-season growing |
| 2 | 6′ x 12′ x 6.5′ Polycarbonate Greenhouse | $594.99 | 76.7 sq ft | 4mm polycarbonate | Large home gardens |
| 3 | 6′ x 8′ x 6.4′ Polycarbonate Greenhouse | $454.99 | 49.6 sq ft | 4mm twin-wall polycarbonate | Better heat retention |
| 4 | 6′ x 6′ x 6.5′ Polycarbonate Greenhouse | $369.99 | 38.9 sq ft | 4mm polycarbonate | Compact, easy-to-heat setups |
| 5 | 6′ x 4′ Walk-In Polycarbonate Greenhouse | $299.99 | 27 sq ft | 4mm twin-wall polycarbonate | Small yards and side yards |
Note: All prices are in Canadian dollars and correct at time of writing. Confirm price and stock before ordering. Size is floor area, calculated from each greenhouse’s listed length and width.
1. Outsunny 6′ x 10′ Polycarbonate Greenhouse for All-Season Growing [2]
| Feature | Details |
| Dimensions | 122.8″ L x 74.8″ W x 79.1″ H |
| Frame | Powder-coated aluminum alloy |
| Panels | 4mm polycarbonate |
| Door | 1 sliding door, 23.6″ W x 63.6″ H |
| Ventilation | 2 hinged roof vents and 1 window |
| Base | Galvanized steel base |
| Wind rating | Level 5 |
| Extras | Built-in rain gutters |
Few greenhouses balance size, strength and airflow as well as the Outsunny 6′ x 10′ x 6.6′ Polycarbonate Greenhouse. There is room for raised beds along both sides with a walkway down the middle. Gardeners who want one greenhouse to use from early spring right through winter will find it a dependable all-rounder.
Pros
- Two roof vents and a window keep air moving on bright winter days.
- Highest wind rating of our five picks, so it handles gusty sites well.
- Galvanized base keeps the frame square and steady on the ground.
Cons
- Assembly takes most of a day, so plan for two people.
- Needs a level, open site with room to walk around all sides.
Best for: Gardeners who want one dependable greenhouse for every season.
2. Outsunny 6′ x 12′ Polycarbonate Greenhouse with Twin Roof Vents [3]
| Feature | Details |
| Dimensions | 147.6″ L x 74.8″ W x 78.3″ H |
| Frame | Aluminum alloy |
| Panels | 4mm UV-resistant polycarbonate |
| Door | 1 sliding door, 24″ W x 64.6″ H |
| Ventilation | 2 roof vents with 5 adjustable opening levels |
| Base | Galvanized steel base with 4 ground bolts |
| Wind rating | Level 4 |
| Extras | Built-in rain gutters |
When one bed of tomatoes turns into three, the Outsunny 6′ x 12′ x 6.5′ Polycarbonate Greenhouse gives you room to keep expanding. Its long layout fits benches on one side and in-ground beds on the other. Serious home growers can run seedlings, summer crops and winter greens all under one roof.
Pros
- Largest growing space on our list, with room for beds and benches.
- Five vent settings give fine control over temperature in every season.
- Bolted base gives the frame a firm hold on windy days.
Cons
- Long footprint needs a large, level area in the yard.
- Higher price than the smaller picks, so it suits committed growers.
Best for: Serious home growers who need room for beds, benches and seedlings.
3. Outsunny 6′ x 8′ Twin-Wall Polycarbonate Greenhouse for Cold Nights [4]
| Feature | Details |
| Dimensions | 8′ L x 6.2′ W x 6.4′ H |
| Frame | Powder-coated aluminum with reinforced poles |
| Panels | 4mm twin-wall UV-resistant polycarbonate |
| Door | 1 hinged door with bolt, 24.25″ W x 63.25″ H |
| Ventilation | 1 adjustable roof vent |
| Base | Galvanized steel base |
| Extras | Built-in rain gutters |
Cold spring and fall nights are where the Outsunny 6′ x 8′ x 6.4′ Polycarbonate Greenhouse earns its place. Its charcoal grey frame gives it a sleek look that blends into most backyards. A mid-size footprint leaves room for shelving, a few grow bags and a small potting area without taking over the yard.
Pros
- Twin-wall panels hold heat better through cold nights than single-wall panels.
- Rain gutters collect water for your plants.
- Bolted hinged door closes firmly against wind.
Cons
- One roof vent, so open the door on very warm days for extra airflow.
- Panel assembly takes time, so set aside a weekend.
Best for: Gardeners who want better heat retention through spring and fall nights.
4. Outsunny 6′ x 6′ Polycarbonate Greenhouse with Galvanized Base [5]
| Feature | Details |
| Dimensions | 74.8″ L x 74.8″ W x 78.7″ H |
| Frame | Aluminum alloy |
| Panels | 4mm UV-resistant polycarbonate |
| Door | 1 sliding door, 24.4″ W x 64.6″ H |
| Ventilation | 2 vents with 5 adjustable opening levels |
| Base | Galvanized steel base with 4 ground bolts |
| Wind rating | Level 4 |
| Extras | Built-in rain gutters |
Compact and evenly shaped, the Outsunny 6′ x 6′ x 6.5′ Polycarbonate Greenhouse fits neatly into a corner of the yard. Its square footprint makes the most of every inch of floor space. Herbs, salad greens and potted plants all have room on benches around the edges, with space to stand in the middle.
Pros
- Small enclosed volume warms quickly and costs less to heat.
- Two vents with five settings let you fine-tune airflow.
- Bolted galvanized base adds stability on windy sites.
Cons
- Floor space suits benches and pots rather than long crop rows.
- Two people are needed for assembly.
Best for: Corner spots and gardeners who plan to heat their greenhouse in winter.
5. Outsunny 6′ x 4′ Walk-In Polycarbonate Greenhouse for Small Yards [6]
| Feature | Details |
| Dimensions | 76″ L x 51.2″ W x 80.7″ H |
| Frame | Powder-coated aluminum alloy |
| Panels | 4mm twin-wall polycarbonate, about 90% light transmission |
| Door | 1 sliding door, 24.6″ W x 65″ H |
| Ventilation | 1 roof window with 5 adjustable opening levels |
| Base | Foundation plate with ground stakes |
| Extras | Built-in rain gutters |
Even a narrow side yard or small patio can hold the Outsunny 6′ x 4′ Walk-In Polycarbonate Greenhouse. Unlike shelf-style mini greenhouses, it still lets you step inside to water and tend your plants. Seedlings, herbs and salad greens grow well here, making it an easy first step into year-round gardening.
Pros
- Twin-wall panels let in plenty of light while holding warmth.
- Foundation plate and stakes keep it steady on open ground.
- Lowest price of our five year-round picks.
Cons
- Compact interior fits one person working at a time.
- Single roof window, so prop the door open on hot summer days.
Best for: Small yards, side yards and first-time year-round growers.
What Can You Grow in a Year-Round Greenhouse?
You can grow something in every season, as long as you match crops to how warm your greenhouse stays. An unheated greenhouse suits cool-season crops such as lettuce, spinach, cabbage and broccoli, while a heated and vented greenhouse can grow warm-season crops such as tomatoes and cucumbers.[7]
| Season | What to Grow |
| Spring | Seedlings for the garden, lettuce, radishes and peas |
| Summer | Tomatoes, peppers, cucumbers and basil |
| Fall | Kale, spinach, lettuce and other salad greens |
| Winter, unheated | Spinach, kale and other cold-hardy greens |
| Winter, heated | Tomatoes, cucumbers and herbs |
How Do You Keep a Year-Round Greenhouse Warm in Winter?
The best way to keep a greenhouse warm in winter is to hold in the heat you already have before adding more. Insulating curtains used at night can cut heat loss by up to 65% through the roof and 35% through the side walls.[8]
- Insulate at night: Line the inside with bubble wrap or hang a thermal curtain on cold nights.
- Add thermal mass: Dark barrels of water soak up heat by day and release it after dark.
- Seal gaps: Check panel clips, door edges and vents for drafts before the first frost.
- Heat with a thermostat: A small heater set to turn on near freezing protects plants without wasting power.
- Keep the roof clear: Brush off snow after each snowfall so light can reach your plants.
Which Year-Round Greenhouse Should You Buy?
The Outsunny 6′ x 10′ x 6.6′ Polycarbonate Greenhouse is the best year-round pick for most Canadian backyards at $549.99. Choose the 6′ x 12′ for the most growing space, the 6′ x 8′ for better heat retention, the 6′ x 6′ for a compact setup that is easy to heat, or the 6′ x 4′ Walk-In for small yards.
Find a year-round greenhouse for your backyard with Aosom Canada, with free shipping on most orders and 30 days to return.
FAQs
With good care, a polycarbonate greenhouse can last 10 years or more. The panels hold up longest when they are cleaned each spring, kept clear of snow and checked for loose clips or screws after every big storm.
Not always. An unheated greenhouse runs on sunlight alone for spring, summer and fall. For winter growing, a nearby outdoor outlet lets you add a small heater, heat mats or grow lights for the short, dark days.
Open the roof vent for a short time on sunny days to let moist air escape. Water early in the morning, space plants apart for airflow, and avoid overwatering, since damp air on cold nights turns into dripping water.
Yes, if the surface is level and strong enough. Bolt the base to a patio with masonry anchors instead of ground stakes, and check that a wooden deck can carry the full weight of the greenhouse, pots and wet soil.
For hardy greens like spinach and kale, keeping the greenhouse just above freezing is often enough. Warm-season crops like tomatoes need a heated greenhouse that stays well above 10°C, especially overnight in January.
References
[1] UMass Extension Greenhouse Crops and Floriculture Program. Ventilation for Greenhouses.
https://www.umass.edu/agriculture-food-environment/greenhouse-floriculture/fact-sheets/ventilation-for-greenhouses
[2] Outsunny 6′ x 10′ x 6.6′ Polycarbonate Greenhouse, Walk-In Green House Kit, Galvanized Sheet Aluminum Frame with Rain Gutter, Vents and Sliding Door, Green, product page.
https://www.aosom.ca/item/outsunny-10-x-6-x-7-walk-in-plant-greenhouse-for-backyard-outdoor-use-with-window-and-door-aluminum-frame-pc-board~1AD12HLRLFG00.html
[3] Outsunny 6′ x 12′ x 6.5′ Polycarbonate Greenhouse with Aluminum Frame, Adjustable Roof Vent, Galvanized Base, Sliding Door and Rain Gutter, Grey, product page.
https://www.aosom.ca/item/outsunny-6-x-12-x-6-5-polycarbonate-greenhouse-walk-in-green-house-with-adjustable-roof-vent-galvanized-base-sliding~1R0EH83S46001.html
[4] Outsunny 6′ x 8′ x 6.4′ Polycarbonate Greenhouse, Aluminum Walk-In Green House Kit with Rain Gutter and Roof Vent, Charcoal Grey, product page.
https://www.aosom.ca/item/outsunny-8-x-6-x-6-4-walk-in-garden-greenhouse-polycarbonate-panels-plants-flower-growth-shed-cold-frame-outdoor~1QLGB4CCKAG01.html
[5] Outsunny 6′ x 6′ x 6.5′ Polycarbonate Greenhouse with Adjustable Roof Vent, Galvanized Base, Sliding Door and Rain Gutter, Grey, product page.
https://www.aosom.ca/item/outsunny-6-x-6-x-6-5-polycarbonate-greenhouse-walk-in-green-house-with-adjustable-roof-vent-galvanized-base-sliding~1VQ7UGH2K2001.html
[6] Outsunny 6′ x 4′ Walk-In Polycarbonate Greenhouse with Sliding Door, Window, Aluminium Frame and Foundation, Silver, product page.
https://www.aosom.ca/item/outsunny-6-x-4-walk-in-greenhouse-polycarbonate-greenhouse-with-sliding-door-window-aluminium-frame-foundation-silver~1KM9F4KTS5O00.html
[7] University of Georgia Cooperative Extension. Grow Fresh Vegetables All Winter Long.
https://fieldreport.caes.uga.edu/?p=19641
[8] Manitoba Agriculture. Greenhouse Heating and Venting.
https://gov.mb.ca/agriculture/crops/crop-management/heating-and-venting.html