Installing a polytunnel greenhouse and ventilating it properly: 5 points

To install a tunnel greenhouse and ensure good ventilation, choose stable ground, secure the planned anchorage, and adjust openings according to the weather. A continuously closed greenhouse can become too hot in the sun and then too humid. The cover also does not guarantee protection against frost.

These five points cover location, securing, cover tension, ventilation, and inspections. This guide is for a small unheated garden greenhouse. Wind, snow, and assembly limits should always follow the model's instructions.

1. Choose the location before assembling the arches

Find a bright area suitable for your intended crops, keeping seasonal shade from buildings and trees in mind. A pleasant spot in the morning can become very hot in the afternoon. Ensure you can monitor plants without having to access them through a difficult area.

Choose ground where water does not collect. The greenhouse should not receive runoff from a slope or gutter. Prepare a sufficiently level surface so that the structure rests correctly and the openings do not warp.

Leave space around it to secure cords, inspect the cover, and open windows. A greenhouse squeezed between a hedge and a wall can lose a large part of its ventilation capabilities. Also, check access to the door with a crate of plants or a watering can.

Familiarize yourself with local regulations before installation. Regulations and land rules depend on the situation; they cannot be deduced solely from the word "demountable." Do not anchor into the ground without checking for underground utilities and elements.

2. Assemble and anchor the structure without relying on the cover

Sort the elements and follow the indicated assembly order. Join the parts without forcing any piece that seems incorrectly oriented. The arches and reinforcements must form a regular structure before installing the cover.

The Manuzen model, reference 845-148, measures 2.95 × 1.95 × 1.96 m and offers an advertised ground area of 5.75 m². Its structure is made of galvanized steel, with four arches and lateral reinforcements. It includes four cords and four anchoring stakes.

The presence of stakes in the package does not guarantee their effectiveness on all types of ground. Stability depends on the soil, exposure, and manufacturer's instructions. If the soil does not properly hold the planned anchorage, seek an appropriate solution rather than using the greenhouse anyway.

Check for plumb, diagonals, and stability according to the instructions. The cover should not be used to forcibly straighten a misaligned structure. Avoid erecting the greenhouse during windy conditions: the cover can become difficult to control.

3. Install the cover while keeping openings clear

The advertised cover is made of 140 g/m² high-density polyethylene. Position it correctly, with the door and windows facing their respective locations. Avoid pulling on a zipper to correct a misalignment.

Stretch it gradually and distribute the fasteners according to the planned assembly. A large pocket on the roof can retain water; excessive tension can strain the seams. Aim for an even distribution without heavily creasing the corners.

The model includes an advertised 15 cm cover extension. Its treatment must follow the instructions and terrain constraints. Do not assume that burying an edge replaces other anchors or that a well-stretched cover can withstand any gust.

Check the operation of the door and the six roll-up side windows with mosquito nets. Do not store equipment in front of them. An opening theoretically present but blocked by a pot or bag does not genuinely contribute to ventilation.

4. Ventilate the tunnel greenhouse according to sun and humidity

Observe internal conditions, not just the advertised outside temperature. Autumn sun can quickly heat a small closed greenhouse. A thermometer placed according to its instructions helps with monitoring but does not provide a universal threshold suitable for all plants.

Use the windows and door to renew the air when conditions allow. Openings on multiple sides facilitate circulation but must be compatible with the wind. A wide-open door facing a gust can stress the structure.

Condensation on the cover indicates humid air in contact with a cold surface. It does not require the same response at all times but suggests reviewing ventilation, plant density, and watering. Avoid constantly maintaining wet leaves and stagnant air.

In cool periods, adjust evening closing based on crops and forecasts, then resume monitoring the next day. An unheated greenhouse does not guarantee frost-free temperatures. Sensitive plants may require different protection or relocation to a suitable place.

Maintain a passage between pots and prune or space plants when their growth obstructs airflow. Do not rely solely on the six windows if the interior is entirely cluttered.

5. Inspect the entire structure after bad weather

After heavy rain or wind, check the anchoring points, cords, fittings, and cover tension. Look for friction areas and small snags before they enlarge.

Follow the manufacturer's recommendations for sheltering or dismantling when the weather exceeds the product's limits. No quantified wind resistance is documented here. Do not wait for the structure to deform before deciding on its use during severe weather.

Clean with a method compatible with polyethylene. The product sheet advises against pesticides that may damage the cover; more broadly, avoid products not validated for use on the cover. Allow to dry before dismantled storage.

Note the openings used and the observed conditions for a few days. This routine helps adjust ventilation to your terrain and crops, without depending on the same schedule all year round.

Key takeaway: installing a tunnel greenhouse and ensuring good ventilation requires a suitable location, reliable anchoring, and regular monitoring. Compare dimensions and openings, then organize their use before filling the greenhouse with plants.

To prepare your project, find our garden equipment and compare features useful for your needs.

Guide documented on September 6, 2026. Situational illustrations generated; product card visual from the product sheet. Model compatibilities and instructions remain decisive.