High Tunnel Greenhouse

High Tunnel Greenhouse – a strong, spacious growing structure for vegetables, seedlings and a longer season

Our Bloomcabin High Tunnel Greenhouse is designed for growers in the USA who want generous protected growing space without relying on a lightweight seasonal polytunnel. The fixed polycarbonate covering, reinforced zinc-coated steel frame and close arch spacing create a practical structure for intensive home or small-scale growing.

The tunnel is approximately 9 ft 10 in wide and 6 ft 11 in high. The base length is approximately 13 ft 1½ in and can be extended in sections of about 6 ft 6¾ in. The Omega-shaped steel profiles are about 2.2 in wide and 0.039 in thick, arches are spaced approximately 3 ft 3 in apart and each arch is anchored about 13.8 in into the ground. The structure is rated for a snow load of up to approximately 32.8 psf. Explore our Greenhouses & Conservatories and Useful Information.

More substantial than a basic polytunnel and more growing volume than many compact garden greenhouses

This model focuses on practical growing capacity, structural strength and the ability to extend the tunnel as your planting plans develop.

Key specifications of the Bloomcabin High Tunnel Greenhouse

Width: approximately 9 ft 10 in (3.00 m).

Height: approximately 6 ft 11 in (2.10 m).

Length: base model approximately 13 ft 1½ in (4 m), extendable in approximately 6 ft 6¾ in (2 m) sections.

Frame: zinc-coated steel, approximately 0.039 in (1 mm) thick.

Profile: Omega-shaped profile, approximately 2.2 in (56 mm) wide.

Arch spacing: approximately 3 ft 3 in (1 m).

Snow-load capacity: up to approximately 32.8 psf (160 kg/m²).

Ground anchoring: each arch extends approximately 13.8 in (35 cm) into the ground.

Covering: 0.24-in (6 mm) polycarbonate with UV protection.

Access: 1 front door.

Ventilation: 2 side windows for airflow and temperature control.

Warranty: 10 years according to the applicable product terms.

A front door and two side windows help you manage both daily access and the growing climate

The tunnel height provides comfortable headroom for working and gives tall crops such as tomatoes and cucumbers the vertical space they need.

Two side windows provide additional airflow. Ventilation becomes especially important on bright days because a protected growing structure can heat up quickly.

Opening the side vents at the right time helps manage heat and humidity while maintaining better air movement around dense plant growth.

A high tunnel can support much more than one crop or one season

The generous width, extendable length and useful working height allow the interior to be organised around several different growing strategies.

Choose the site, prepare the ground and think about ventilation before the frame goes up

Choose a reasonably level position with good sunlight and enough clearance from trees, walls and other obstructions.

Because each arch is anchored about 13.8 in into the ground, make sure the ground is suitable and check for buried services or other obstacles before installation.

Plan paths, irrigation and convenient access to the front door before deciding the final tunnel length.

For more planning and ordering guidance, see our Useful Information.

When does a high tunnel make more sense than a classic aluminium greenhouse?

A classic aluminium greenhouse places more emphasis on architectural appearance, colour choices, glazing options and integration with the landscaped garden.

The High Tunnel focuses on productive protected growing space, robust functionality and straightforward modular expansion. Its width stays constant while the tunnel grows by adding length.

Choose the High Tunnel when crop production and protected growing volume are the priority. Choose a classic greenhouse when visual customisation and a more architectural garden feature matter more.

Use the same structure differently in northern, humid, hot, and dry regions

A high tunnel in Maine or Minnesota has a very different job from the same structure in Texas, Georgia, California, or the Mountain West. Northern growers may value earlier spring planting and a later fall harvest, while hot southern locations often need aggressive ventilation and careful summer crop selection.

In humid regions, keeping rain off foliage can be valuable, but trapped humidity must still be removed. In arid climates, the polycarbonate shell protects crops from wind and weather while making irrigation entirely dependent on the grower.

That regional variation is why the tunnel should be managed as a controlled growing space rather than as a one-size-fits-all greenhouse. Track your own sun exposure, frost pattern, summer heat, wind, and water availability before deciding how to use it.

Choose sun and access first, then think about the direction of prevailing winds

For most U.S. home gardens, a sunny site with unobstructed exposure is the best starting point. Morning sun is especially useful after cool nights, while adequate afternoon ventilation becomes critical in warmer regions.

Wind exposure should also influence placement. Avoid narrow gaps between buildings where wind speeds can accelerate. In open rural properties, a distant windbreak may help without shading the tunnel or blocking airflow around it.

Because every arch is anchored about 13.8 inches into the ground, locate buried electrical lines, irrigation, drainage, gas, or other utilities before installation. The anchoring depth is a structural feature and should not be shortened simply to avoid difficult ground.

Use protected space for early greens first and warm-season crops later

In colder states, the tunnel can earn its space long before tomatoes are ready to transplant. Early lettuce, spinach, herbs, brassica starts, and other cool-season crops can occupy the beds while outdoor soil is still less dependable.

As days lengthen and nights warm, those early crops can give way to tomatoes, cucumbers, peppers, or other heat-loving plants. Late in the season, sections can return to greens and fall crops after summer plants are removed.

This succession strategy turns the tunnel into a multi-season production area instead of a structure used for only one summer crop. Actual planting dates should follow local conditions, not a national calendar.

In the South and Southwest, ventilation can matter more than extra heat

In hot climates, a rigid polycarbonate tunnel can become too warm quickly if it is treated like a closed winter greenhouse. Side vents should be opened early enough to prevent excessive heat buildup rather than after plants are already stressed.

Irrigation timing also matters. Watering near the root zone in the morning can reduce unnecessary humidity compared with repeatedly wetting foliage late in the day. In very sunny locations, temporary shading may be useful during the hottest part of the season.

Growers in warm regions may use the tunnel most intensively in fall, winter, and spring rather than trying to force every crop through peak summer heat. The structure is flexible enough to support that seasonal shift.

Plan irrigation before plants fill the 9 ft 10 in width

The polycarbonate roof keeps rainfall from watering the beds directly. Drip lines or other targeted irrigation are therefore easier to install before crops, stakes, and trellises occupy the interior.

A longer tunnel can be divided into irrigation zones so tomatoes, cucumbers, seedlings, and lower-water crops are not all forced onto the same schedule. Soil texture should guide how long and how often each zone runs.

If rainwater storage is part of the plan, place tanks where they do not shade the tunnel or interfere with the front door. In drought-prone regions, storage capacity and backup water supply deserve as much attention as the greenhouse itself.

The 32.8 psf rating is a design value, not a reason to ignore winter storms

In northern and mountain states, snow can vary dramatically in density. Wet snow and wind-drifted accumulation can create very different loads from light powder even when the visible depth looks similar.

Inspect the tunnel after significant storms. Look for uneven accumulation, unusual frame movement, loose fasteners, or damage around vents. If snow must be removed, use a method that does not scratch or point-load the polycarbonate panels.

Before winter, check ground anchoring, M5 fasteners, D40 tabs, reinforcements, door alignment, and vent hardware. Preventive inspection is much easier than making repairs during a prolonged freeze.

Plan the 13 ft 1½ in base and 6 ft 6¾ in modules around your actual garden workflow

The base tunnel is long enough to create distinct growing zones, but the modular design makes expansion possible if production increases. Before adding sections, ask whether you also have the irrigation capacity, compost, trellising, and time to manage the extra space.

Keep one end of the structure clear if future expansion is likely. That may affect where permanent paths, fences, water tanks, and raised beds are placed outside the tunnel.

For a home gardener, a shorter structure may be easier to manage intensively. For a market garden or serious self-sufficiency project, additional modules can create a more efficient protected production row.

Anchoring is only one part of keeping the tunnel reliable in exposed locations

High winds can stress doors, vents, panels, and connections even when the ground anchors remain secure. After severe weather, inspect the entire shell rather than looking only at whether the tunnel is still upright.

Keep side vents closed and secured when conditions call for it, and make sure the front door latches properly. Loose components can create movement that becomes more damaging during repeated gusts.

If your property is routinely exposed to severe wind, local site conditions may justify additional professional advice on placement and protection. The standard structure should always be installed according to the product instructions.

Use the same 3 m structure differently depending on how much you harvest

A family garden may dedicate one side to tomatoes and cucumbers while keeping the other side flexible for herbs, peppers, or seasonal greens. A small farm may prefer repeatable bed widths, drip zones, and trellis lines that continue through several modules.

The tunnel works best when access is kept clear. Avoid filling every inch with containers or beds if that makes harvesting and ventilation difficult. A usable path is part of productive square footage because it allows plants to be maintained properly.

Before commercial or regulated use, check any local requirements that apply to the structure, electrical work, water systems, or farm operation in your area.

FAQ – Bloomcabin High Tunnel Greenhouse