Specify a cover that controls incoming light while fitting the way your greenhouse moves air, opens and closes. A dark sheet alone does not establish a dependable blackout system.
DERFLEX supplies greenhouse covering materials and custom tarpaulin options for commercial growers, greenhouse fabricators and OEM buyers. Discuss black/white film, opaque coated-fabric constructions, custom panel sizes and reinforced finishing against your project drawing. Approve light blocking, handling weight and seam details together before bulk production.
Roll goods & fabricated-panel enquiries · Project-specific sample approval
A greenhouse blackout tarp is an opaque covering used to create a controlled dark period. Its light-blocking construction, edge closures and ventilation arrangement work together to support the grower’s photoperiod plan.
For crops such as chrysanthemums and poinsettias, the grower sets the required dark interval and acceptable light exposure. Material selection should follow those requirements rather than a generic “black tarp” label. Purdue Extension explains photoperiod control and blackout-cloth use.
It needs verified low light transmission through the sheet, a closure layout that prevents edge and seam leaks, and a compatible way to manage heat and humidity while covered. UV resistance, dark color and high GSM do not establish blackout performance by themselves.
Separate the need for darkness from the need for weather protection, low curtain weight or water-vapor movement. A heavier cover can increase handling and drive loads without correcting a gap around a door.
The matrix compares material families. It is a selection guide, not a list of tested DERFLEX blackout grades.
| Material family | Where to consider it | Key trade-off | Approval priority |
|---|---|---|---|
| Black/white PE film | Light-deprivation covers where low sheet mass and broad coverage matter. | A solid barrier needs a separate air-exchange strategy. Punctures, folds and attachment edges need attention. | Opacity, UV suitability, tear behavior and repeated-handling sample. |
| Opaque reinforced PE tarp | Removable covers needing a reinforcing textile or scrim. | Reinforcement helps carry handling loads; weave and color still do not prove blackout. | Coating continuity, crease damage, perimeter fixing and seam light leaks. |
| Opaque PVC-coated polyester | Reusable fabricated panels, reinforced side curtains and welded cover assemblies. | Weight and bending stiffness can increase roller torque and packed volume. A solid coating is not a breathable climate screen. | Actual opacity, cold flexibility, compatible welds and system load limits. |
| Purpose-made interior blackout screen | Retractable greenhouse curtain systems needing low packed volume and specified moisture behavior. | Specialist structures vary. “Breathable” does not mean unrestricted airflow or automatic condensation control. | System-supplier compatibility, measured light transmission, air/vapor properties and edge seals. |
| Ordinary shade cloth | Daytime light reduction and crop shading. | Open shade fabric transmits light and generally cannot deliver a controlled dark period. | Use a separate blackout layer when the crop programme requires darkness. |
For solid fabricated covers, review the underlying PVC tarpaulin material options. For daytime shading, see greenhouse shade fabric.
An opaque sheet can still leave a bright line at a seam, bottom edge or ventilation opening. Identify whether light passes through the material or around it; the corrective action is different.
Inspect the closed assembly under the outside-light conditions it will encounter. Include the fan-on state and every position of the curtain travel.
| Observed symptom | Likely source | Detail to review |
|---|---|---|
| Diffuse glow across a panel | Insufficient sheet opacity or local coating variation. | Test the material away from edges, then compare it with the approved sample using the agreed measurement method. |
| Bright line between panels | Insufficient overlap, seam opening or exposed stitch holes. | Review the closure through its full travel. Use a compatible welded joint or an opaque backing detail where the assembly requires it. |
| Light around roof or end-wall edges | The moving curtain does not meet the fixed perimeter seal. | Draw the junction in section, including brackets, rails and the closed stop position. Allow for movement without a direct light path. |
| Flashes near the lower edge | Wind lift, fan pressure or an uneven base opens the skirt. | Check the lower seal and retention under operating pressure. Add support or a designed sealing profile instead of excessive point tension. |
| Glow at a door, zipper or pipe | Uncovered access closure or service penetration. | Review opaque flaps, sealed collars or a baffled entry. Test the detail after repeated opening and closing. |
| Bright vent or fan opening | A direct line of sight through the air path. | Use a designed light trap and verify fan performance with the added resistance. |
| Pinpoints after repeated folding | Abrasion, punctures or crease-related damage. | Inspect contact points and folds. Repair using an approved opaque, material-compatible construction and repeat the light check. |
Specify an overlap detail, not a universal overlap number. Required coverage depends on geometry, tension, movement and closure accuracy. A larger loose overlap can still open under pressure. Show its orientation and sealed position on the drawing.
For frequently used access points, the zippered tarp construction guide explains useful layouts. A zipper still needs a light-blocking closure detail when used in a blackout assembly.
A solid blackout tarp restricts air exchange through the covered area. Design the intake, exhaust and moisture strategy for the closed condition; the white outer face alone cannot keep a sealed greenhouse cool.
Purpose-made screen fabrics and solid films behave differently. The NGMA curtain-systems guide distinguishes impermeable PE film from porous curtain constructions.
Locate openings outside the curtain’s travel. Fit light traps where daylight would otherwise enter; avoid uncovered gaps used as improvised vents.
Baffles, filters, insect screens and ducting add resistance. Select the fan at the actual operating static pressure and verify delivered airflow with the blackout system closed.
Circulation fans mix air; they do not replace outside-air exchange or dehumidification. Track crop-zone temperature and humidity during the dark interval.
Prevent sagging areas that can collect leaks or condensate. Anti-drip treatment changes droplet behavior; it does not remove water vapor or replace drainage.
Blackout curtain fabric is repeatedly bent, pulled and stored. Approve the moving assembly as well as the flat material sample. For a separate daylight roof layer, review greenhouse films and covering options.
Use a panel layout that operators can move without dragging over rough fasteners or sharp frame edges.
Seams, pockets and patches can create uneven roll buildup. Greater thickness is not automatically an upgrade.
Sliding or suspended systems require compatible curtain weight, flexibility and packed dimensions.
There is no universal GSM, thickness or shade percentage that proves the completed greenhouse is dark enough.
Agree on the crop-zone acceptance criteria with the grower, then ask the supplier to confirm the material and fabrication details below.
| Specification item | What to define | How it affects the order |
|---|---|---|
| Material & layer structure | Black/white film, reinforced PE or opaque coated polyester; identify the light-blocking layer and face orientation. | Controls fabrication route, handling and application suitability. |
| Light transmission | Target, spectral range, direct/diffuse conditions, detector sensitivity and method; sample, seams and installed assembly assessed separately. | Do not substitute a UV rating or visual color judgment for an agreed opacity check. |
| Mass & thickness | GSM and/or thickness with tolerances; finished panel mass where system loading matters. | Confirm the selected grade. No blanket weight or mil recommendation applies to every system. |
| Width, length & cut plan | Available roll width, seam positions, finished size and tolerances; separate cutting size from installed coverage. | Determines seam count, waste, shipping volume and installation fit. |
| Mechanical requirements | Tensile/tear direction, seam strength, edge pull resistance, bending and abrasion exposure. | Agree the relevant method and acceptance values before approval. |
| UV & temperature | Internal or external exposure, local climate, movement temperature and any required aging evaluation. | UV treatment and cold-flex behavior must suit the actual operating environment. |
| Seals & accessories | Welds, hems, pockets, reinforced attachment zones, flaps, collars and fastener positions. | Put light-sealing details and attachment geometry on the drawing. |
| Air/vapor behavior | Solid barrier or specialist screen; any requested permeability result plus the greenhouse ventilation arrangement. | A sheet property cannot establish whole-greenhouse airflow. |
| FR & chemical exposure | Required fire-test standard, permitted cleaners and exposure to crop-protection products. | Grade-specific evidence and compatibility require confirmation; no blanket certification is implied. |
| Supply & packaging | Rolls or fabricated panels, quantity, identification, rolling/folding direction and destination. | MOQ, price, sample plan, lead time and packing are quoted against the confirmed specification. |
A greenhouse’s plan width is not the cover path over the roof. Measure along the intended route, then identify end-wall drops, side skirts, closures and moving overlaps. Label every panel, fixed edge and operating face.
For replacement covers, an old stretched or torn panel is a reference; confirm its dimensions against the frame and hardware.
These original DERFLEX website photographs show coated fabrics and roll materials. Approve the specified blackout grade through a sample and test plan; a material photo cannot demonstrate greenhouse light transmission.
Use the same material, seam, reinforcement and closure details intended for production. Combine supplier sample checks with commissioning in the actual greenhouse.
Inspect for pinholes and coating variation. Agree how light transmission will be measured and reported, including detection limits.
Make a seam, hem, pocket and closure mock-up. Evaluate light blocking and mechanical integrity after representative flexing.
With normal fans operating, inspect crop-height points near edges, doors and vents under relevant outside-light conditions.
Retain sample identity, drawing revision, agreed readings, closure positions and repair method for future replacement orders.
Review DERFLEX’s material quality-control process, then agree the specific blackout and finished-panel checks required for this order.
DERFLEX can review covering materials, custom dimensions, reinforced edges and fabricated tarp details. Send the project scope so material supply, finished-panel work and greenhouse-system responsibilities are clear.
Request a representative sample and, where relevant, a fabricated mock-up. MOQ and lead time depend on the selected construction, custom formulation, size, finishing and order quantity; confirm them in the quotation.
Polymer and reinforcement, layer construction, usable width, total area, cutting yield, seam count, reinforcement and required testing all influence cost. Compare quotes against the same finished specification and supply scope.
Use panel IDs, operating-face labels, drawing revisions and a retained approved sample. Review whether rolled packing or controlled folds better suit the material and installation sequence.
Direct answers to the questions that change material selection and installation details.
Ask about your applicationOnly if its opacity and the completed closure meet the project requirement. Black color alone does not establish blackout performance. Check the sheet, seams, edges, doors and ventilation openings under the intended outside-light conditions.
No. Ordinary shade cloth reduces light and usually has an open structure. Blackout cloth is selected to create a controlled dark period. A high shading percentage does not by itself prove the crop zone meets a blackout requirement.
There is no universal value. Select opacity, tear behavior, flexibility and handling weight together, then confirm compatibility with the cover mechanism. Greater thickness or GSM can add load without improving edge sealing or light control.
A white or reflective face commonly faces solar exposure to reduce absorbed heat, while a dark functional layer provides light blocking. Follow the selected construction’s installation instructions and verify opacity in that orientation. Ventilation remains necessary.
Use an intake and exhaust arrangement with suitable light traps or baffled air paths. Include their resistance when selecting the fan, and check airflow and crop-zone conditions with the blackout cover fully closed.
Solid PE film and solid PVC-coated tarp should not be treated as breathable greenhouse climate screens. Purpose-made blackout screens can have different air and vapor properties. Request relevant test data and design greenhouse ventilation separately.
Close the system under the relevant outside-light conditions and inspect seams, edges, doors, vents and penetrations with normal fans operating. Use visual checks to locate defects and a suitable calibrated detector to assess agreed crop-zone acceptance limits.
DERFLEX accepts enquiries for greenhouse covering materials and custom tarp options. Provide the construction, dimensions, quantities, closure details and destination. Confirm the available blackout grade, sample plan, fabrication scope, MOQ and lead time with the quotation.
Technical reading: Purdue Extension — Managing Photoperiod in the Greenhouse; NGMA — Internal and External Greenhouse Curtain Systems. These references inform the application guidance; they are not DERFLEX product certifications.
Share the cover path, operating system, opacity requirement and quantity. Request a material proposal and the sample checks needed for your application.