Sigma Medium Greenhouse

Mid-Size Backyard Kits, 8 ft Wide

4.8 · 412 reviews
Save $400
Sigma 250 (Gen III) greenhouse in a garden setting with trees and flowers
Metal Sigma 250 (Gen III) greenhouse structure in a warehouse setting - Planta Greenhouses EU.
Sigma 250 (Gen III) greenhouse with transparent panels in a warehouse setting
Clear polycarbonate Sigma 250 (Gen III) greenhouse in a garden with flowers and plants around
Sigma 250 (Gen III) greenhouse in a garden with trees and flowers around
Metallic Sigma 250 (Gen III) greenhouse structure in a warehouse setting with shelves and boxes in the background.
Modern Sigma 250 (Gen III) greenhouse with transparent walls and a metal frame, surrounded by greenery.
Metallic Sigma 250 (Gen III) greenhouse with a sliding door in an indoor setting
Sigma 250 (Gen III) Greenhouse in a garden with trees and flowers
Sigma 250 (Gen III) greenhouse with a sliding door in an indoor setting
Metal Sigma 250 (Gen III) greenhouse structure in a warehouse setting
Arc-shaped Sigma 250 (Gen III) greenhouse with a person inside, surrounded by trees and greenery.
Roll of metal sheet on a Sigma 250 (Gen III) greenhouse with a textured background
Interior of a Sigma 250 (Gen III) greenhouse with curved walls and a door.
Interior of a Sigma 200 (Gen III) greenhouse with shelves and a ladder.
Partial view of a Sigma 200 (Gen III) greenhouse with a sliding door
Sigma Medium Greenhouse
Metallic framed door for Sigma 250 (Gen III) greenhouses with a latch mechanism

Sigma Medium 26

Sigma Medium greenhouse kits are arched backyard greenhouses rated for a 265 kg/m² (55 psf, 4.5 ft) snow load and 100 km/h wind, with 6 mm twin-wall polycarbonate panels and a 10-year warranty. They're for sale in 4 sizes, all 8 ft wide, so you can choose the length that fits your space. Find your greenhouse.

Size: Sigma Medium 26 · 8′ × 26′Size guide
$5,550$5,950Save $400
Free shippingTo nearest terminal
10-year warrantyFrame & panels
Pre-cut panelsFor easier installation
Guided assemblyVideos and live chat
Questions? Talk to a grower.

Mon–Fri 9am–5pm EST or Send a Message

Call us1-877-669-1286

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Which size is best for your garden?

Get this sizing guide with photos and bed layouts.

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pg guide cover
  • Insulated Doors NEW – Helps reduce heat loss and drafts, creating a more stable growing environment and improving energy efficiency.
  • Upgraded Door Handles NEW – Smooth, reliable operation with a sturdy grip for easier daily access and long-term durability.
  • Aluminum Polycarbonate Trim NEW – Securely locks panels in place along the arch for added strength, better weather resistance, and a clean, finished look.
  • Window/Door Latch NEW - Makes the door and window open together.
  • Improved Snow Load [NEW] - Rated for a snow load of up to 265 kg/m² (55 psf, 4.5 ft).
  • Wind resistant up to 100 km/h for those living in gusty climates.
  • Comes with two doors (one at each end).
  • Made with a heavy-duty galvanized steel frame and 6 mm twin-wall polycarbonate panels.
  • Arched shape - helps wind, snow and hail slide off the sides.
  • Extendable beyond 100 ft - so you can expand your greenhouse when you're ready.
  • Maintenance-free means you have more time to focus on your garden.
  • We offer a 10-year warranty because our greenhouse is heavy-duty and long-lasting.
  • Access to our private Facebook group to connect with and learn from other greenhouse owners.
  • The Sigma Medium Greenhouse is available in 4 size configurations. Plus, you may purchase an extension kit, to extend the length of the greenhouse.
  • Extendable & Customizable
  • Snow Load Up To 265 kg/m² (55 psf, 4.5 ft) 
  • Wind Resistant up to 100 km/h
  • We offer a 10-year warranty because our greenhouse is heavy-duty and long-lasting.

Greenhouses are amazing products, and they require special shipping and handling. That is the reason, we have been working diligently over the past year to secure preferential shipping rates for our customers. Most shipments across Canada and the US are between $250 and $450. 

  • We will contact you to confirm shipping price, based on your location and order size.
  • Shipping on most residential greenhouse orders is between $250 and $450, customers in remote areas may need to pay extra.
  • When you place your order, please make sure to enter the correct Phone and Address at checkout. You will be contacted by phone before the item is shipped. We cannot be responsible for deliveries to incorrect addresses.
  • As part of the delivery process, we require a contactable telephone number (for the courier company to contact you) before the item is shipped.
  • White glove delivery service isn't available. The greenhouse components are delivered in multiple boxes, the largest of which weighs 80lbs. The greenhouse will be delivered to your driveway. Please make arrangements to have the package moved to its installation location. 
  • We do not ship to PO Boxes, as in most cases you will need to sign for your item.  
  • Orders placed on weekends or public holidays will not begin processing until the next business day. 

 

Free guide

The Beginner's Guide for Greenhouse Owners

Tell us where to send it and it's yours.

Sigma Medium Greenhouse Measurements

Sigma Medium 26 · 8′ × 26′

3D view
Side view

Compare Sigma Medium Greenhouse Sizes

This greenhouse comes in several size configurations. Every greenhouse extends in 6.5 ft sections, so pick the length that fits your plot and your plans.
Sigma Medium Urban greenhouse, 8 ft × 13 ft, at the end of a stone path Sigma Medium Urban
8′ × 13′
Sigma Medium 20 greenhouse, 8 ft × 20 ft, on a patio beside a lawn Sigma Medium 20
8′ × 20′
Sigma Medium greenhouse with a roof window open, in a garden with flowers and shrubs Sigma Medium 26
8′ × 26′
Sigma Medium greenhouse on a patio with flower beds in front Sigma Medium 32
8′ × 32′
Price
Sale$3,950
$3,750
Sale$4,950
$4,650
Sale$5,950
$5,550
Sale$7,050
$6,450
About
A bed along each side with a center path: greens, herbs and a few tomato plants.
Long side beds and a short bench for seedlings and potted plants.
Room for side beds, trellised crops and a small potting area.
The largest Sigma Medium: several crop zones plus space for benches and a heater.
Width
8 ft width
8 ft width
8 ft width
8 ft width
Length
13 ft length
20 ft length
26 ft length
32 ft length
Height
7.5 ft height
7.5 ft height
7.5 ft height
7.5 ft height
Sq ft
104 sq ft
160 sq ft
208 sq ft
256 sq ft
Owner reviews
4.8 Read all 412 reviews
Read all 412 reviews
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Dome-shaped Greenhouse
About this model

Dome-shaped Greenhouse

Sigma greenhouse has a dome-shaped arch which sheds snow and rain, and the galvanized steel frame with 6 mm twin-wall panels is rated for 55 psf of snow. Insulated doors help keep the warmth in.

Winter-Ready Greenhouses
Why Planta Greenhouses

Winter-Ready Greenhouses

Heavy-duty greenhouses used by 25,000+ growers since 2019, designed to withstand heavy winters. Backed by a 10-year warranty and live customer support.

Arrives in labeled boxes
Shipping & assembly

Arrives in labeled boxes

Ships across Canada, and most residential orders ship for $250–$450 depending on your location. Every panel is pre-cut and every bag of hardware is labeled, so two people can build it with the step-by-step videos.

Questions? Talk to a grower.

Mon–Fri 9am–5pm EST or Send a Message

Call us 1-877-669-1286