What mil greenhouse plastic should I buy?

For any covered structure you want to last more than one season, 6 mil is the right choice. Thinner 3–4 mil co-poly film is cheap but only rated for a single season; 6 mil greenhouse-grade polyethylene carries a 4-year UV warranty and handles wind, hail, and installation stress far better. Woven 8 or 11 mil is worth it for large commercial tunnels or high-wind sites where the extra tear resistance pays off.

How long does greenhouse plastic last?

Standard 6 mil greenhouse-grade polyethylene is warranted for 4 years against UV degradation. In practice, with proper installation (no contact with raw aluminum or PVC), most growers get 4–6 years. Budget co-poly film (3–4 mil) lasts one season. Woven 8–11 mil film from manufacturers like Solarig can exceed 5 years under normal use.

What is the difference between clear and diffused greenhouse plastic?

Clear film transmits 88–91% PAR light in a direct beam: ideal for maximum winter brightness. High-diffusion film scatters light more evenly through the canopy, trading a few points of total transmission (77–88% PAR) for better light distribution. Diffused film reduces plant shadows and hot spots, which benefits flowering crops and dense plantings. For cold-climate season extension, clear film usually wins in winter; diffused film wins in summer tunnel production.

Does greenhouse plastic with IR additive actually save on heating costs?

Yes, with a measurable difference. Infrared additives trap outgoing radiant heat from soil and plant surfaces at night, delivering 10–20% heating savings depending on cloud cover. The UMass Extension cites the cost premium at only a couple of cents per square foot, with payback measured in weeks for a heated greenhouse running through winter. For unheated tunnels, the benefit is smaller but still real on cold, clear nights when radiant heat loss is highest.

Can I put greenhouse plastic directly on aluminum framing?

Yes, but there is one critical exception: do not let 6 mil polyethylene contact raw PVC pipe or fittings. PVC's plasticizers migrate into the poly film and accelerate UV breakdown, often cutting the 4-year warranty to one or two seasons. Use aluminum or galvanized steel channels, or add a poly tape or batten strap barrier anywhere the film contacts PVC.

Greenhouse Plastic: Mil, UV Life, and Which Film to Buy

Greenhouse plastic is the one consumable part of a structure that can last a decade. Buy the wrong film and you’re back on the ground two years earlier than you needed to be, re-covering a structure that cost ten times as much as the plastic. The decision tree is not complicated, but the terminology (mil, UV rating, IR additive, anti-drip, diffusion) creates enough confusion that people default to whatever is cheapest and regret it.

This page decodes the spec sheet.

Mil thickness: what it actually measures

Mil is not millimeters. One mil is one-thousandth of an inch. A 6 mil film is 0.006 inches, about 0.15mm. That sounds trivial, but the difference between 4 mil and 6 mil is roughly the difference between one season and four.

The standard commercial greenhouse film is 6 mil. It handles installation tension, wind flutter, hail impact, and moderate debris contact without tearing. It can be re-used if you pull it carefully at season end. Most 6 mil films carry a 4-year UV warranty when installed correctly.

Below 6 mil, you’re in co-poly territory: 3 and 4 mil films designed for single-season use in row covers and low tunnels, not permanent structures. They’re cheap ($0.03–0.06/sq ft), but they degrade visibly in 8–12 months under UV load. They are not appropriate for a high tunnel or a permanent hoop structure. Don’t let a low price tag make that trade look appealing.

Above 6 mil, woven films (8 mil, 11 mil) use a polyethylene weave reinforcement inside the film layer for dramatically higher tear resistance. If you’re covering a 30-foot-wide tunnel in a coastal wind zone, or you want a film that survives a crew re-covering without a single puncture, the woven option earns its premium.

A long high tunnel with white polyethylene film cover in a vegetable field, crops visible through the end — A commercial high tunnel with standard 6 mil poly. On a structure like this, the right film choice matters: a single-season film on a 96-foot tunnel means re-covering every spring. A 4-year-rated 6 mil means you do it every four or five. *USDAgov via Flickr. CC BY 2.0.*

What the UV rating actually means

Greenhouse-grade 6 mil film carries a 4-year UV warranty, which means the manufacturer stands behind the film’s structural integrity against UV-induced degradation for four full years of outdoor exposure. That rating is tied to the UV stabilizer package in the film: typically HALS (hindered amine light stabilizers) and UV absorber compounds added at the time of manufacture.

The UMass Extension puts the cost premium on warranted greenhouse film vs. co-poly plainly: it’s roughly double the price per square foot, but the math runs the other direction on multi-year structures. A 4-year film at $0.12/sq ft costs $0.03/sq ft/year. A co-poly film at $0.04/sq ft that you replace every season costs $0.04/sq ft/year plus the labor to re-cover (UMass Extension, “Plastic Greenhouse Film Update,” verified June 2026).

Bootstrap Farmer’s standard 6 mil clear runs from $75 for the smallest cut to $1,199 for a full roll, carrying a 4-year UV warranty and 95% UV blocking at 350nm (Bootstrap Farmer product page, verified June 2026). It is a 5-layer film with anti-dust treatment to maintain light transmission over time.

One installation note that matters for warranty validity: do not allow 6 mil polyethylene to contact raw PVC pipe or fittings. PVC plasticizers migrate into the poly film and accelerate UV breakdown, often halving the effective life. Use aluminum or galvanized steel channel to secure the film, and add a batten tape or poly-tape barrier at any PVC contact point.

Light transmission: the number that feeds your plants

All greenhouse poly films transmit light, but not the same way. The UMass Extension publishes the practical PAR transmission ranges:

Standard UV-stabilized 6 mil clear: 88–91% light transmission
IR-AC (anti-condensate) film: 82–87%
IR-AC with diffusion: 77–88%

The difference between 88% and 82% doesn’t sound dramatic, but UMass is direct about the implication: “one percent increase in light equals one percent increase in plant growth during the winter.” On a crop that needs every photon it can get in December and January, the clearest available film is often the right call.

Bootstrap Farmer’s standard 6 mil clear tests at 89% light transmission with 21% diffusion. Their high-diffusion 6 mil (from $142.99) trades peak transmission for a more even canopy distribution; the five-layer construction includes anti-drip, anti-dust, and high-diffusion additives designed for floral and fruiting crops where shadow banding from direct sun can cause uneven development.

For cold-climate season extension (the grower who wants maximum light in the short days of November through February), clear film wins. For summer tunnel production of tomatoes and peppers where hot spots and uneven ripening are real problems, diffused film is worth the trade, often paired with an exterior layer of reflective shade cloth once midsummer sun pushes interior temperatures too high.

Film type	Typical price/sq ft	UV rating	Light transmission	Diffusion	Best for
Co-poly 4 mil	~$0.03–0.05	1 season	90–92%	Low	Single-season row cover
6 mil clear (standard)	~$0.10–0.15	4 years	88–91%	Low	Year-round tunnels, winter growing
6 mil high-diffusion	~$0.17–0.25	4 years	77–88%	20–40%	Florals, fruiting crops, summer
Woven 8 mil	~$0.25–0.35	4–5 years	85–89%	Moderate	High-wind sites, commercial
Woven 11 mil	~$0.35–0.50	5+ years	83–87%	Moderate	Large-span, coastal, high-abuse

Prices based on Bootstrap Farmer collection page, verified June 2026. Per-sq-ft cost calculated on mid-size cut.

Inside a commercial glasshouse with even diffused overhead light and organized rows of growing crops — Even overhead light distribution inside a commercial growing house. The absence of shadow banding across the beds is the visible payoff from diffused glazing: light scattered through the canopy reaches more of the growing surface. For leafy crops and high-density plantings, this distribution benefit often outweighs the small reduction in total transmission. *Natalia Sevruk via Pexels. Pexels License.*

IR additives: the spec that changes the heating bill

Infrared (IR) additives are the most misunderstood feature on a greenhouse film spec sheet. They don’t generate heat. They slow down radiant heat loss.

Here’s what happens in an uninsulated single-layer greenhouse at night: the soil, the growing medium, and the plant tissue all radiate thermal energy outward. Without IR additives, polyethylene film is nearly transparent to that wavelength: it passes right through, warming the outside air instead of the inside. IR additives absorb or reflect that long-wave thermal radiation back into the structure.

The UMass Extension quantifies the effect at 10–20% heating savings in a heated greenhouse, depending on sky condition. On clear nights, radiant heat loss is the dominant mechanism, which is exactly when IR additives work best. On cloudy nights, cloud cover provides its own radiant barrier and the benefit shrinks. For a greenhouse that costs $800/season to heat, 15% savings is $120/year. At a cost premium of “a couple of cents per square foot” (UMass), the payback on even a modest tunnel is one or two seasons.

Bootstrap Farmer’s High Diffusion 6 mil includes IR additives as part of its five-layer construction. If you’re heating a high tunnel and you’re comparing clear vs. high-diffusion, the IR layer in the diffusion film partially offsets the lower light transmission through reduced overnight heat loss. For the full BTU math on what those heating savings mean in dollars, the greenhouse heating guide covers those calculations by glazing type and structure size.

Anti-drip: real benefit, limited duration

Anti-drip (anti-condensate) coatings reduce the surface tension of the film interior, causing condensation to run down to the edges rather than forming individual droplets. Droplets reduce light transmission by scatter, and they can drip onto crops: a minor cosmetic issue for greens, a real problem for fruiting crops prone to botrytis.

The honest limitation: UMass notes that anti-drip coatings typically last two to three years before the surfactant is depleted. A 4-year film with anti-drip is providing that benefit for the first half of its life. Factor that in if you’re choosing between two otherwise similar films where anti-drip is the differentiator.

Replacing greenhouse plastic: when and how

Greenhouse film on a properly maintained tunnel typically gives visible signs before it fails: cloudiness or yellowing (UV degradation), surface crazing or small cracks, loss of elasticity at the seams. Most growers who track their installation year pull the film at year 4 before failure rather than after.

Replace in late summer or early fall, when mild temperatures keep the poly flexible enough to work with and the growing season gives you time before hard frost. Film installed in cold weather is stiff, prone to cracking during tensioning, and difficult to get wrinkle-free.

When you pull the old film, inspect the hip board, wiggle wire channel, and any PVC contact points. Any spot where the old film shows accelerated degradation along the edge is a signal that PVC was in contact; protect that zone before re-covering.

Bootstrap Farmer sells the full installation supply chain: batten strap, Wellington tape, and repair tape for mid-season patches. For a standard hoophouse re-covering, budget one roll of repair tape per 50 linear feet of hip seam as a supply buffer.

For the structure under the plastic (whether a Bootstrap Farmer high tunnel kit, a DIY pipe frame, or a rigid-frame greenhouse), our greenhouse foundation guide covers the base and anchoring requirements that determine whether your covering job lasts. For rigid twin-wall or triple-wall polycarbonate panels instead of poly film, the Exaco Riga review compares the premium kit options side by side. If you’re choosing between covering a high tunnel vs. a framed polycarbonate kit, our high tunnel vs. greenhouse kit guide frames that decision by growing space per dollar and climate zone.

Close-up of greenhouse plastic being secured with wiggle wire and channel on an aluminum frame — Wiggle wire channel and hip board installation. Getting the tensioning right at the base matters as much as the film quality; slack poly vibrates in wind and degrades faster at contact points than drum-tight poly does. *Acabashi via Wikimedia Commons. CC BY-SA 4.0.*

Bootstrap Farmer: the verified source for film and supplies

Bootstrap Farmer carries the full range: 6 mil clear ($75+), High Diffusion 6 mil ($142.99+), woven 8 mil Solarig 156 ($230.99+), and woven 11 mil Solarig 182 ($306.99+), plus batten strap, repair tape, and installation accessories. Prices verified on their collection page, June 2026. Bootstrap Farmer runs a 10% affiliate commission program (verified via their Shopify Collabs page), and their pricing is competitive on commercial-scale purchases. All URLs here are plain (no tracking parameters).

The Bootstrap Farmer greenhouse plastic page lists current widths and lengths for each film type, and they ship free to the contiguous US on orders over $75. For large rolls that exceed 120 lbs, expect motor freight; factor in delivery timeline when planning a cover replacement.

One product note: if you’re comparing Bootstrap Farmer’s 6 mil to other vendors, check whether the competing product is UV-stabilized greenhouse-grade or co-poly. Prices that look significantly cheaper per square foot are almost always co-poly (single-season) or an inferior UV package. The 4-year warranty is the quality signal worth paying for.

Accessories worth buying on day one

A good film does most of the work, but a few low-cost items protect the cover and the crop under it.

Stainless steel greenhouse panel clips: hold rigid polycarbonate panels in their channels so wind flutter does not pop one loose mid-season.
Agribon AG-19 floating row cover: a few degrees of extra protection inside the tunnel on the coldest nights, when the film alone is not enough.
Ashman auger ground anchors: keep a hoop frame or covered structure from lifting and racking before drum-tight poly has a chance to degrade at the contact points.

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