20 by 40 foot Quonset greenhouse in a landscaped garden

Rounded High Tunnel Greenhouse Kit

$1,129.00 $1,800.00

Available to order SKU: qhut12x12

Width

Length

Ventilation

Even in mild climates, your greenhouse will need ventilation. The affordable, low-tech manual side roll-up systems work by allowing you to roll up the long sides of your greenhouse and allow fresh air to roll through.

If you want more control in your environment, then powered fans and fresh-air intakes are the choice for you.

Many customers get both, but typically one or the other is fine.

None $0.00 No additional ventilation package.

Manual Side Roll-Up Ventilation Kit Each kit comes with (2) geared roll-up handles capable of rolling up 300', enough roll-up pipe for each side, billow strapping to hold your system down in the wind, and EZ strapping clips.

Powered Fans Our fans help regulate temperature, humidity, and air circulation, creating optimal conditions for plant growth. They run off of normal 110 plug-ins.

Fan size

Fresh Air Intakes Non-powered vents installed opposite your exhaust fan allow cooler, fresh air into the greenhouse. Unless you have a manual side roll-up system, your powered fans will need them.

Intake size

Metal End-Wall Kit Package

Add galvanized metal framing kits for both the front and back ends of your greenhouse.

None $0.00 No metal end-wall framing package.

Metal End Wall Kit Our easy-to-install, bolt-together end-wall kits have two major advantages compared with building wood ends: they last longer and are much faster to install. You will typically save about a day of installation time.

Greenhouse Plastic

Choose the standard greenhouse covering or upgrade to heavier string-reinforced plastic.

Standard 6 mil Greenhouse Plastic Included The standard UV greenhouse covering included with the base kit.

10 mil String Reinforced Plastic Upgrade +10% of base kit This is the most heavy duty plastic on Earth! If you want the strongest cover possible for your greenhouse, it's worth every penny.

Configured Total

Base greenhouse$1,129.00

Ventilation$0.00

Front & back metal end-wall package$0.00

10 mil string-reinforced plastic upgrade$0.00

Configured total$1,129.00

Request a Detailed Quote

Available installment options are provided by the store’s active financing provider.

Greenhouses Sold & Delivered

10-Year Frame Warranty

Helpful Assembly Support

Product overview

Rounded greenhouse growing, simplified.

The Sunbow Rounded High Tunnel is a straightforward, versatile greenhouse kit built in Oregon with American-made galvanized steel. Its rounded hoops help wind move smoothly over the structure, making it an excellent choice for windy areas. The smooth Quonset profile creates a dependable growing space for backyard gardens, farms, nurseries and commercial growers.

Greenhouse kit includes: 16-gauge galvanized steel hoops with 4′ spacing, three rows of 1⅜″ purlins, all connectors needed for assembly, a complete wiggle wire system used to attach the plastic to the frame, and 6 mil UV greenhouse plastic covering with a 4-year warranty.

Choose the width and length that fit your site, then build out the ventilation and end-wall options around the way you grow. The rounded design makes efficient use of materials while providing generous covered space and a practical structure that can scale from a compact garden greenhouse to a larger farm installation.

Rounded High Tunnels are available in 12′, 16′, 20′ and 24′ widths.

Product photos may show customer-supplied doors, lumber and site improvements. Your itemized quote will clearly list everything included with your kit.

Complete your greenhouse

Recommended Accessories

Three practical additions that make installation, climate control and everyday greenhouse use easier.

$29.99

Ground Stake Driver

Really makes driving ground stakes a breeze and is worth every penny. A traditional T-post driver will not work with most of our ground stakes because they are too short.

For 1⅝″ ground posts
For 1⅞″ ground posts

Explore this accessory

Starting at $59.00

Shade Cloth

Our shade cloth comes in 30%–70% shading, with various sizes to fit any greenhouse. If you need help figuring out which shade cloth is best for you, please reach out.

You can also place your main order online and we can help you add it later.

Shop shade cloth

Weed and landscape fabric installed between greenhouse crop rows

From $49.99

Weed Barrier Fabric

Commercial-grade 3.2 oz UV-resistant landscape fabric: a chemical-free weed barrier.

Landscape fabric is a versatile and eco-friendly solution for keeping weeds at bay in your garden or landscaping. Unlike chemical-based weed killers, this fabric acts as a physical barrier, preventing sunlight from reaching the soil and inhibiting weed growth.

Explore this accessory

Verified product data

Dimensions and Technical Specifications

Installation & Assembly Manual	Download instruction manual (PDF)
Peak Height	8′–12′ depending on the width chosen. Any unit can be made up to 12′ high.
Tunnel Width	12′, 16′, 20′ and 24′
Tunnel Lengths	Any length in 4′ increments
Bow Spacing	4′
Bow Diameter	1⅜″ 16-gauge galvanized steel
Ground Stakes	1⅝″ 16-gauge galvanized steel
Greenhouse Plastic	6 mil UV greenhouse covering · 4-year warranty. A 10 mil string-reinforced plastic upgrade is available.
Baseboards	All lumber is supplied by the customer
Purlins	1⅜″ 16-gauge galvanized steel
Estimated Assembly Time	Varies by greenhouse size and crew — typically 2–5 days
NRCS Specifications	All of our Rounded greenhouse kits are NRCS compliant.
Delivery	Free delivery within our free delivery area. Nationwide shipping is available beyond that, starting at $399. Request a shipping quote for your project.