The cover is the actual greenhouse. The rest of the components, the frame, the vents, and the benching, exist only to hold up the covering material, since it is the cover that creates the actual greenhouse effect. Fail at this point, and you will be losing heat, preventing too much light, wearing out prematurely, or spending triple what you should have. Here we talk about the options for greenhouse cover material, building a DIY cover, waterproofing your greenhouse cover outdoors, and using greenhouse cover for planters.
Greenhouse Cover Material: What the Options Actually Are
Every greenhouse cover material involves tradeoffs between light transmission, heat retention, durability, and cost. Knowing what you’re trading is how you make the right choice.
Filme de Polietileno
Most common greenhouse covering worldwide. Low-cost, flexible, easily fitted onto any shape of frame, and comes in many different thicknesses and formulations. Excellent light transmission capability with standard clear polyethylene having an 85 to 90 percent light transmission capacity.
Disadvantage: standard polyethylene film without any UV inhibitor will break down when exposed to sunlight directly. Greenhouse-quality polyethylene films usually have UV inhibitors and sometimes infrared (IR) coatings, which help in retaining heat during nighttime. The lifespan of film ranges from 2 to 4 years in the case of greenhouse-quality film, while in construction use only lasts for 1 to 2 years as a greenhouse covering.
Recommended for: backyard greenhouse covers, hoophouses, temporary structures for gardening purposes, etc.
Painéis de Policarbonato
Two layers or multiple layers of polycarbonate panels provide higher insulation values compared to film (R-values ranging from 1.5 to 2.0 for two-layer panels and up to 3.5 for three-layer panels), good light transmission (70 to 85 percent), and increased longevity.
Drawbacks: high cost compared to film, needs framing that fits the width of the rigid panels, and light diffusion rather than transmission.
Recommended for: permanent or semi-permanent greenhouses where energy conservation is essential and the budget permits.
Vidro
Highest light transmission and permanent construction. The standard material used for commercial greenhouses and top-end hobby greenhouses. Expensive, heavy, and needs sturdy framing.
Recommended for: permanent greenhouses with a solid foundation and framing. Not recommended for DIY greenhouse covers.
Shade Cloth and Row Cover Fabric
Not a weatherproof covering, but worth including. Shade cloth blocks a percentage of light (30 to 90 percent, depending on grade) and is used in summer to prevent heat stress on crops. Row cover fabric is a lightweight spunbond polypropylene that protects against frost without blocking much light.
DIY Greenhouse Cover: Building Your Own Setup
The most accessible DIY greenhouse cover approach uses polyethylene film over a simple hoop or A-frame structure. Here’s how to do it well.
Build the Frame First
Common DIY frame options:
- PVC conduit hoops: Flexible, inexpensive, works for low tunnel and hoop house designs. Size the hoop diameter to the bed width.
- Electrical conduit (EMT): Stiffer than PVC, holds shape better in wind, slightly more complex to bend.
- Lumber A-frame: Simplest structure, easy to build from 2x4s, naturally accommodates flat or ridge-roof panel layouts.
- Rebar stakes with PVC pipe: Drive rebar stakes into the ground, slip PVC over them to create the hoop, then cover.
Whatever frame you use, it needs to be anchored. An unanchored hoop house becomes a sail in the wind, and the cover tears at every contact point.
Applying the Plastic Film Cover
For Hoop Tunnel and Small Greenhouse:
- Measure the film large, 18 to 24 inches on all sides, larger than the framework itself
- Place the film over the framework, starting from the middle of the frame and going outwards
- Tighten the film as you attach it to the ground with dirt, lumber, or ground stakes
- At the end sections, fold the excess film and secure it to an end post
O Lona plástica VEVOR de 6 mil (0,254 mm), 10 x 100 pés (3 x 30,48 m), is practical for a standard hoop tunnel or small A-frame greenhouse. The 10-foot width covers a single hoop bay without a seam, and the 100-foot length accommodates tunnels of up to 30 to 35 feet with appropriate overlap at the ends.
For wider greenhouse spans — a 12-foot wide hoop house or a large A-frame build — the Lona plástica VEVOR de 6 mil (0,254 mm), 24 x 100 pés (3 x 30,48 m) covers the full width in a single run, eliminating the mid-roof seam that’s a common failure point in wide greenhouse builds.
Waterproof Greenhouse Cover: What to Look For
All solid polyethylene film is technically waterproof. The practical question is how the installation performs under real rain and condensation loads, and how long the waterproofing holds under outdoor conditions.
Key factors for a waterproof greenhouse cover:
- Minimum Mil thickness: 6mil for all outdoor applications. The film gets micro-tears at stress points when the mil is too thin to withstand seepage due to excessive rain.
- Film quality: Deteriorated film is affected by sunlight, creating microcracks on the surface. When the film starts turning chalky or cracked, its waterproof ability reduces. Check for UV inhibitors in the film.
- Management of seams and overlaps: The roof ridge or end walls should be arranged to ensure that overlaps shed the water instead of trapping it. Ensure that overlapping sections have upper sections shedding to lower sections only.
- Tension: A slack film accumulates water due to rain pressure, thus getting torn where the accumulation occurs. Always have sufficient tension on the film.
For a greenhouse cover expected to handle multiple seasons without replacement, the Lona plástica VEVOR de 10 mil (0,254 mm), 10 x 100 pés (3 x 30,48 m) offers the additional thickness and durability that extends the useful life compared to standard 6mil film.
Greenhouse Cover for Planter: Small-Scale Applications
Not every growing project needs a full structure. A greenhouse cover for a single raised bed or container planter is a scaled-down version of the same principle: a film cover over a small frame to extend the growing season, protect against frost, or create a warm microclimate for seedlings.
How to Build a Planter Greenhouse Cover
- Cut pieces from PVC pipes or wires to form an arch over the planting space that can either be hammered into the ground or inserted into holes made on the sides of the raised bed.
- Place the arches at distances of 2-3 feet apart within the planting space
- Cover the arches with plastic sheets and secure them at the sides and ends
- One side must be loosely attached to allow easy lifting when necessary
For smaller planter covers, the Lona plástica VEVOR de 4 mil (0,254 mm), 3 x 50 pés (3 x 30,48 m) is the practical size. The 3-foot width covers a standard raised bed width without excess, and 4mil is adequate for a sheltered planter application where the film isn’t exposed to sustained wind or heavy rain loads.
Ventilation Is Non-Negotiable
Even on a small planter cover, heat buildup on a sunny day can damage or kill seedlings faster than frost would. Build in a way to open the cover during the day or use row cover fabric (spunbond poly) instead of solid film for daytime use in spring and fall.
Perguntas Frequentes
How long does polyethylene film last in a greenhouse?
Standard construction film: one to two seasons in direct sun. Greenhouse-grade UV-stabilized film: two to four seasons. Heavy-duty 10mil film with UV inhibitors: three to five seasons in most climates. Direct UV exposure is the primary degrading factor.
Should I use clear or white plastic for a greenhouse cover?
Clear film transmits the most light and is the default for growing applications. White or opaque film diffuses light and reduces heat buildup, which is beneficial in hot climates or summer growing, but reduces photosynthetic potential in low-light seasons.
Does a plastic greenhouse cover need ventilation holes?
Solid PE film has no built-in ventilation. You need to create ventilation by having openable end walls, removable panels, or roll-up sides. Sealed plastic greenhouses overheat rapidly in spring and summer sun and will damage plants.
Can I use standard black plastic sheeting as a greenhouse cover?
Black film absorbs rather than transmits light, which makes it unsuitable as a cover for a plant-growing greenhouse. It works well as ground cover inside a greenhouse to suppress weeds and retain soil heat, but not as the roof material.
How do I repair a tear in a plastic greenhouse cover?
Use polyethylene repair tape (UV-resistant outdoor tape) applied to both sides of the tear on a clean, dry surface. Temporary repairs hold reasonably well on lower-stress areas of the cover. A tear at a ridge line or tension point usually means the cover needs replacing in that section.
Conclusão
To get the best out of your greenhouse cover, it’s important to select one that’s suitable for the job at hand. If you’re constructing a greenhouse for your own home or garden, 6 mil polyethylene film is the way to go. This type of film will do the job and last for more than one season. If you need a cover for several years, use 10 mil. The VEVOR 6mil Plastic Sheeting range, in both 10-foot and 24-foot widths, covers the full range of DIY greenhouse builds, and the VEVOR 10mil Plastic Sheeting is the right step up when durability is the priority.
