Written by: Vincent

Oval vs Round Greenhouse Tubes: Why Oval Wins

When designing a professional greenhouse, every structural choice affects performance, longevity, and crop results. Among these choices, none impacts overall efficiency more than the shape of the steel arches.

Traditional greenhouse frames use round or square steel tubes. While functional, these profiles limit structural performance, restrict luminosity, and add long-term operational costs.

Today, the oval tube greenhouse represents the most advanced step forward in greenhouse engineering. Thanks to its optimized geometry, the oval tube delivers exceptional strength, increased light transmission, longer poly-film life, faster installation, and unique design advantages such as safe drilling in the neutral axis; a feature not possible with round or square tubing.

This article explains why the oval tube greenhouse has become the preferred choice for commercial growers across Canada, the northern U.S., and demanding climates worldwide.

Oval Tube Greenhouses: Superior Strength, Maximum Luminosity, and Smarter Engineering

What Makes the Oval Tube Different?

The oval tube is engineered with a wider, flatter profile that increases bending stiffness, distributes snow and wind loads more efficiently, and reduces deformation under pressure. This brings significant structural advantages over round or square tubes.

For the same quantity of steel, oval tubing is:

28% stronger than round tubing
46% stronger than square tubing
18% stronger than rectangular tubing

These performance gains allow greenhouses to span wider distances, use fewer arches, reduce internal shading, and maintain structural integrity under severe climate conditions.

In regions like Ontario, Quebec, Alberta, Michigan, Montana, and Pennsylvania, where snow loads and winds challenge every structure,the oval tube has proven to be one of the most reliable and cost-efficient options on the market.

Superior Structural Resistance Under Snow and Wind Loads

Greenhouses in northern climates must withstand extreme loads. Snow accumulation, rapid freeze–thaw cycles, and strong winds can quickly reveal weaknesses in traditional round or square tubing.

The oval tube excels under these conditions because of its:

higher bending stiffness
lower deformation under load
aerodynamic profile that reduces wind suction
wider stress-distribution area

These qualities allow growers to build stronger greenhouses without increasing steel weight; a major advantage when aiming for optimal cost-performance balance.

A structure that holds its shape under pressure also keeps its poly cover tighter and more resistant to flapping, abrasion, and tearing. The result: fewer repairs and a significantly longer structural lifespan.

Better Light Transmission = More Yield

Light is one of the most valuable resources in a greenhouse. Any shading from the structure directly reduces crop productivity.

Because the oval tube is naturally stronger, arches can be spaced farther apart than in round- or square-tube designs, without sacrificing strength or safety. This reduces the number of shadows cast onto the growing area.

More light reaching the crop canopy increases yield potential, especially in winter.

1% more light ≈ 1% more yield

Corenthin Chassouant, M.Sc., Agronomist & Greenhouse Expert

This makes the oval tube greenhouse not just a structural upgrade, but a direct contributor to crop performance and profitability.

mooth Profile = Longer Poly Film Life

Polyethylene film is one of the most frequent replacement items in greenhouse operations. Square or rectangular tubes contain edges that create friction, wearing the film faster and causing tears.

Oval tubes solve this by offering:

a smooth, edge-free surface
Reduced friction during installation
minimal film movement wear
improved tension uniformity

This leads to fewer film replacements and lower long-term operating costs. For growers operating multiple acres, the savings quickly become significant.

Faster Installation and Better Material Efficiency

Oval tubes make greenhouse installation faster and easier thanks to:

fewer arches
Reduced steel usage
wider spans between posts
simplified assembly with bolted joints
less on-site drilling

Because the arches are more spread out, the greenhouse requires fewer structural elements, which reduces:

material cost
installation time
labour cost
freight volume

This is why oval tube greenhouses are preferred by professional installers and high-volume growers looking to optimize ROI.

Drilling in the Neutral Axis

One of the most overlooked advantages of the oval tube is its ability to be drilled safely through the neutral axis, a low-stress zone where drilling does not weaken the structural capacity.

This is only possible with oval tubes because:

The neutral axis is wider and more accessible.
Stress distribution is optimal due to the oval geometry.
Drilling can be performed without compromising the bending resistance.

Round and square tubes do not offer this advantage:

Their neutral axis is too narrow.
Drilling risks penetrating high-stress areas
It can weaken the arch and reduce load capacity.

Why this matters for commercial greenhouses

Drilling safely through the neutral axis allows Harnois to design:

swedged (crimped) tubes that fit precisely
bolted assemblies instead of self-drilling screws
longer-lasting, more secure connections
factory-precision joints with reduced on-site drilling

This results in a cleaner, stronger assembly and ensures long-term structural stability.

Luminosa Structural Gutter: Perfect Complement to the Oval Tube

The Luminosa greenhouse, Harnois’ high-luminosity gutter-connected system, integrates advanced oval tubes with a modern, engineered structural gutter system.

This gutter is not just a rain channel. It is a primary structural beam that enhances overall greenhouse performance.

Key Luminosa Gutter Advantages

Structural Load Distribution

The gutter transfers snow and wind loads across all posts, reinforcing the greenhouse’s rigidity and long-term stability.

Reduced Shading and Thermal Bridges

Its optimized, narrower profile decreases shadows inside the greenhouse while minimizing thermal bridges, critical for winter energy efficiency.

Wide 9½-inch walking surface

Harnois’ design offers:

safer worker access during poly installation
comfortable footing for maintenance
faster and safer re-covers

This is a unique advantage not found in many competitor gutter systems.

Superior Water Managemen

The Luminosa gutter handles:

efficient rainfall evacuation
optional condensation gutter separation
improved interior climate control

Reducing condensation drip prevents disease spread, improves crop quality, and supports a healthier growing environment.

Ideal Applications for Oval Tube Greenhouses

Oval tube structures are best suited for:

commercial vegetable and fruit production
high-tunnel berry systems
multi-span gutter-connected greenhouses
heavy-load crop systems (tomatoes, cucumbers, peppers)
northern climates with snow load requirements

Harnois uses oval tubes across its most advanced greenhouse models:

TunnelPro Plus (freestanding tunnel system)
Ovaltech (reinforced freestanding greenhouse)
Luminosa (high-transmission gutter-connected structure)

Each structure leverages the strength, efficiency, and long-term performance advantages of the oval profile.

The Oval Tube Greenhouse Is the Best Structural Choice

The oval tube greenhouse represents a major advancement in greenhouse engineering. Its unique shape delivers benefits unmatched by round or square tubes:

Higher structural strength per pound of steel
Wider arch spacing and more natural light
Longer-lasting poly film
Reduced installation and labour costs
Safe drilling in the neutral axis
Superior gutter integration in Luminosa models

For growers in northern climates, or anyone seeking a high-performance structure that maximizes ROI and yield, the oval tube greenhouse is simply the strongest, smartest, and most efficient solution.

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