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What Is a High Tunnel Greenhouse? Benefits, ROI & Uses

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  • A high tunnel greenhouse extends the growing season by weeks or even months, allowing earlier and later harvests.
  • With improved yields and lower inputs, it offers a return on investment in as little as three years.
  • Harnois’ TunnelPro Plus is designed for durability, ventilation, and full equipment access.

High-tunnel greenhouses, also called hoop houses, are a popular choice for growers looking to extend their growing season and improve their crop yields. These commercial greenhouse structures offer an affordable and effective way to protect crops, boost production, and take control of your growing environment.

At Harnois Greenhouses, we specialize in durable, customizable high tunnel greenhouses that meet the needs of growers across North America. In this blog, we’ll cover everything you need to know about high tunnels and why they might be the perfect fit for your growing operation.

What is a High Tunnel Greenhouse?

A high tunnel greenhouse is a structure designed to provide a controlled environment for growing crops. Unlike traditional greenhouses, high tunnels are usually unheated and rely on natural sunlight to maintain a warm climate. The design typically includes:

 

    • Flexible sizes to suit small farms or large-scale operations.

These structures are ideal for extending the growing season, starting plants earlier in the spring, and even growing year-round in mild climates.

Pros

  • Extended Growing Season
    Grow earlier in the spring and later into the fall without supplemental heating—ideal for northern climates.

  • Improved Yields & Crop Density
    Denser planting and better growing conditions lead to significantly higher output per square foot.

  • Better Crop Quality & Consistency
    Fruits and vegetables are cleaner, more uniform, and less exposed to wind damage or soil splash.

  • Designed for Equipment Access
    TunnelPro Plus offers sufficient clearance for tractors and mechanized tools, saving labor time.

  • Lower Operating Costs
    No need for permanent foundations or costly climate-control systems—fewer moving parts and less maintenance.

  • Reduced Use of Phytosanitary Products
    Drier foliage and soil lead to fewer fungal outbreaks and lower dependence on fungicides and insecticides.

  • Lower Water Consumption & Nutrient Loss
    Drip irrigation under tunnels increases efficiency and reduces leaching, helping you save on water and fertilizer.

  • Fast ROI
    Many TunnelPro Plus customers see a return on investment within three growing seasons, thanks to improved marketability, reduced losses, and operational savings.

  • Durability & Wind Resistance
    Harnois high tunnels are designed to resist strong winds, with robust oval-tube frames that stand up to open-field exposure.

  • Concrete-Free Installation
    Easy to install with helical or plate anchors, requiring no poured foundation.

Cons

  • 3 Seasons Greenhouse
    While excellent against wind, tunnels are not designed to bear heavy snow loads or ice accumulation.

Benefits of High Tunnel Greenhouses

High tunnel greenhouses offer a practical, cost-effective way to improve crop quality, extend the season, and increase farm profitability—without the complexity of a fully climate-controlled greenhouse. Designed for three-season use, these structures help growers manage wind, rainfall, and temperature fluctuations, creating a more stable growing environment. From lower input costs to faster harvesting and improved predictability, the benefits of high tunnels are both agronomic and economic.

Boost Crop Yields

High tunnels create an optimal environment that can increase crop yields by up to 50%. The controlled conditions protect plants from extreme weather, pests, and diseases, ensuring healthier and more productive harvests.

Extend the Growing Season

With a high tunnel, you can start planting weeks earlier and continue harvesting long after the typical growing season ends. Some growers even use high tunnels for winter farming.

Affordable and Quick ROI

High tunnel greenhouses are cost-effective compared to traditional greenhouses. Harnois Greenhouses’ high-tunnel kits have a low start-up cost and provide a fast return on investment.

Versatile for Many Crops

High tunnel greenhouses are great for growing:

High Tunnel Greenhouse

Harnois TunnelPro Plus: High Tunnel Greenhouse Redefined

Unlike basic hoop houses, the TunnelPro Plus was developed with commercial growers in mind. Its curved-wall design offers superior sidewall clearance and higher airflow, while its durable oval-tube structure enables wider spacing between arches—reducing material cost and increasing brightness inside the structure.

Key design features:

  • Minimum of 3 tunnels for layout efficiency

  • Option to add structural gutter between tunnels

  • Can be twinned or extended as needed

  • UV-resistant film with optional anti-drip treatment

  • Adapted for berries, vegetables, herbs, and flowers

Foundation: Screw Piles

High tunnel greenhouses from Harnois are designed to be anchored with screw piles, eliminating the need for poured concrete foundations. This not only reduces installation time and cost but also offers flexibility for relocation or expansion.

Benefits of Screw Piles:

  • No excavation or curing time

  • Fast and clean installation

  • Anchors securely into most soil types

  • Allows reinstallation if the layout changes

  • Reduces environmental impact compared to concrete

This type of foundation is ideal for three-season structures and supports fast deployment—especially in agricultural settings where time and mobility matter.

high
commercial greenhouse size - high polytunnel

Case Study: 15 Hectares of Raspberries with Entreprise Pitre

Harnois partnered with Entreprise Pitre, a leading raspberry grower, to build 15 hectares of TunnelPro Plus high tunnels in Quebec. The results highlight the business case for investing in high tunnels:

  • +30% Yield compared to open-field raspberry production

  • 40% Faster Harvesting due to better access and more uniform fruit ripening

  • 50% Lower Operating Costs, from reduced labor, water, and phytosanitary inputs

  • ROI Within 3 Years, driven by better pricing and operational savings

This installation is a model for berry growers across North America looking to scale sustainably and predictably.

Partnership Spotlight: Dubois Agrinovation

We work closely with Dubois Agrinovation, a trusted agricultural supplier known for irrigation and crop management tools. Through this collaboration, growers benefit from:

  • Integrated drip irrigation systems

  • Shade and insect netting options

  • Ground covers and mulch films

  • Local expertise and logistics

This partnership allows growers to streamline their procurement process and maximize productivity from day one.

What is the difference between a high tunnel greenhouse and a freestanding greenhouse?

Both freestanding greenhouses and high tunnel greenhouses are popular structures for commercial growers—but they serve different purposes and offer distinct benefits depending on your production goals, climate, and budget.

High Tunnel Greenhouse

A high tunnel is a three-season, unheated structure designed to extend the growing season by protecting crops from wind, rain, and temperature fluctuations. It uses passive ventilation and minimal infrastructure, making it ideal for field-scale production of berries, vegetables, and cut flowers.

Freestanding Greenhouse

A freestanding greenhouse is a permanent structure often equipped with heating, cooling, and automation systems. It is suitable for year-round production and is designed to meet building code standards for snow, wind, and structural load.

Which One is Right for You?

  • Choose a high tunnel greenhouse if you want fast ROI, season extension, and efficient crop protection at a lower cost.

  • Choose a freestanding greenhouse if you need full environmental control and year-round production capacity.

Harnois Greenhouses offers both options—with customizable solutions based on your climate, crop, and growth plan. Our team can help assess which structure fits best with your goals.

Steel Quality & Galvanization: Built to Last

Every TunnelPro Plus high tunnel is made using structural-grade steel, with each tube coated in Galvalume for superior corrosion resistance. Harnois goes a step further by adding our proprietary PowerCoat™ finish for extended durability, especially in humid or high-fertility environments.

Why it Matters:

  • Structural-grade 50 ksi steel: Stronger than the industry norm, enabling longer arch spacing and fewer materials

  • Galvalume coating: Combines aluminum and zinc to resist rust 2–4x better than galvanized steel

  • Harnois PowerCoat™ finish: Additional protection against abrasion, condensation, and fertilizer residue

This high-quality steel ensures your high tunnel remains a durable, low-maintenance investment for years to come.

Steel joint and bolts in greenhouse tunnel structure

Oval vs Round Tube: Brighter, Stronger by Design

Harnois uses oval tubes instead of traditional round pipes in its high tunnel greenhouses—and there’s a good reason why. Oval tubing offers a better strength-to-weight ratio, distributes load more efficiently, and reduces interior shading caused by framing.

Advantages of Oval Tubes:

  • Up to 30% stronger than round tubes of similar gauge

  • Wider spacing between arches without sacrificing integrity

  • Fewer shadow lines, allowing more natural light for crops

  • Streamlined airflow, improving ventilation inside the tunnel

This structural innovation not only enhances the longevity of the greenhouse but also contributes to better growing conditions inside.

FAQ - High Tunnel Greenhouses

A high tunnel greenhouse is an unheated, seasonal structure made with steel framing and polyethylene film. It protects crops from wind, rain, and pests, extending the growing season without the complexity or cost of a traditional greenhouse.

Yes, especially in milder climates! Even in colder regions, high tunnels allow for extended seasons with proper planning and crop selection.

Our high tunnels are engineered to withstand heavy snow loads, strong winds, and other extreme conditions, making them a reliable choice for Canadian and North American climates.

No. Most high tunnels use ground anchors or screw piles, eliminating the need for concrete foundations. This allows for fast installation and flexibility if the structure needs to be relocated.

In most climates, high tunnels are best used from early spring to late fall. They are not designed for winter production or to support heavy snow loads unless customized with additional reinforcement and heating.

High tunnels are ideal for small fruits (like raspberries and strawberries), leafy greens, tomatoes, cucumbers, and herbs. They’re also commonly used for cut flowers and nursery starts.

  • Earlier and later harvests

  • Better yield and crop quality

  • Fewer pests and diseases

  • Lower input costs (water, fertilizers, phytosanitary products)

  • Full equipment access

  • Faster return on investment

FAQ About Harnois Greenhouses

All Harnois structures are manufactured in North America, which ensures faster lead times, high material standards, and easier access to parts and support.

In addition to high tunnels, we offer other models like the Luminosa, Ovaltech, and Vermax, each tailored for specific needs.

Absolutely! Our team is here to help with installation, maintenance, and any questions you have about your high tunnel or greenhouse.

Harnois Greenhouses is a Canadian manufacturer with over 60 years of experience designing and fabricating commercial greenhouse structures, including high tunnels, multi-tunnels, and freestanding greenhouses.

Harnois stands out for its oval-tube framing (stronger and brighter by design), North American manufacturing, local service, and its turnkey approach—from design to after-sales support.

Absolutely. Our team evaluates your crop type, climate, location, and business goals to recommend the right structure—whether it’s a high tunnel, freestanding greenhouse, or gutter-connected model.

TunnelPro Plus is a three-season structure not intended to meet building code for permanent buildings. It is, however, designed for wind resistance and long-term durability.

Ready to Build Your High Tunnel Greenhouse?

High tunnel greenhouses are a game-changer for growers looking to increase productivity and profitability. At Harnois Greenhouses, we’re here to help you create the perfect structure for your needs. With over 60 years of experience and full North American service, Harnois offers:

  • Local manufacturing and fast shipping

  • Oval-tube frame design for strength and light transmission

  • Tailored designs for wind resistance and ease of access

  • On-site support for setup and ongoing service

  • Bilingual technical assistance (EN/FR)

Contact us today to get started with a custom quote and discover how a Harnois high tunnel can transform your growing operation.

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