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Greenhouse

ACRYLITE 16 mm Multi-Skin Greenhouse Panels (Resist and Alltop)

The twin-wall acrylic that commercial growers glaze with: 86 percent light in the standard Resist sheet, 91 percent in the wide-rib Alltop, R-2.04 insulation, a NO DRIP coating, and a non-prorated 30-year non-yellowing warranty. Twice the price of polycarbonate and worth it if you are keeping the greenhouse.

4.7
From $1,225 per 5-panel bundle (16 mm clear)
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Pros

  • 86% light transmission (Resist 16 mm) and 89–91% (Alltop 16 mm), against 72–76% for 16 mm polycarbonate
  • Non-prorated, full-replacement warranties: 30 years against yellowing, 10 years on light transmission, 10 years on hail
  • R-2.04, U-0.49 twin-wall insulation; the maker cites up to 40 percent energy savings over single glazing
  • NO DRIP coating spreads condensation into a film instead of drops that scatter light and drip on plants
  • UV-stable through the sheet, so a scratch does not expose unprotected plastic
  • Stiff: a 47-inch-wide 16 mm sheet needs no cross supports for uniform loads to 15.7 lb per sq ft

Cons

  • Roughly double the price of 16 mm polycarbonate, and freight only
  • About 1 lb per sq ft, nearly twice polycarbonate's weight; check the frame
  • Combustible, ASTM D-635 class CC2, with area limits in some codes
  • Moves 1/16 in per foot with heat and moisture; wood battens and screws through the sheet will crack it
  • Seasonal stock-outs are routine, and custom lengths under 20 sheets carry a repacking charge

Specifications

MaterialImpact-modified extruded acrylic (PMMA), double-skin
Light transmissionResist 16 mm clear 86% (Light White 74%, Bronze 53%, Solar Cool White 37%); Alltop UV-absorbing 89%, UV-transmitting 91%
InsulationR-2.04, U-0.49 (16 mm); 8 mm is R-1.78, U-0.56
Rib spacingResist 16 mm 32 mm (1 1/4 in); Alltop 64 mm (2 1/2 in)
Sheet size47 1/4 in (1200 mm) wide; Resist to 36 ft, Alltop to 28 ft; retail lengths 6–16 ft
Weight0.9–1 lb per sq ft (16 mm); 0.7 lb (8 mm)
Thermal movement6 mm per m (1/16 in per ft)
Service temperature160°F max without load
FireASTM D-635 CC2; CAN/ULC S102.2 flame spread under 150; self-ignition 830°F
Sound24 dB weighted reduction (16 mm)
Support16 mm at 1200 mm wide: no cross members to 15.7 lb/sq ft; 8 mm: supports at 106 in
WarrantyNon-prorated full replacement: 30 yr non-yellowing (colorless), 10 yr light transmission, 10 yr hail
PriceGreenhouse Megastore: 16 mm from $1,225 per 5-panel bundle; 8 mm from $745
MakerPolyvantis (the Röhm acrylic business), Sanford, Maine and Germany

Our Verdict

The glazing to buy for a greenhouse you plan to keep for twenty years and heat through winter. Use the aluminum glazing system made for it, order in late winter, and take the Alltop wide-rib version if light matters more than UV blocking.

4.7

Overview

ACRYLITE multi-skin is twin-wall acrylic: two skins of impact-modified acrylic joined by ribs, extruded as one sheet 47 1/4 inches wide and up to 36 feet long. It is the glazing on commercial, research, and institutional greenhouses that chose acrylic over polycarbonate, and it is our Best Overall pick in the greenhouse panel roundup. This review goes deeper into the two 16 mm versions, the published numbers behind them, the warranty that separates them from polycarbonate, and the handling rules that separate a twenty-year roof from a cracked one.

The sheet is made by Polyvantis, the company that took over the Röhm acrylic business; ACRYLITE is the brand in the Americas and PLEXIGLAS everywhere else. It ships from Sanford, Maine and from the plant in Germany. We have not glazed with it. The figures come from the maker's technical sheet and selection chart, a distributor's listing, and university extension data, all listed at the end.

Resist versus Alltop

ACRYLITE Resist is the standard multi-skin: 8 mm with 16 mm ribs, or 16 mm with 32 mm (1 1/4 inch) ribs. Clear 16 mm transmits 86 percent of light; the 8 mm, 84 percent. It is UV-blocking, which is what most growers want, and it comes in Light White (74 percent), Bronze (53), and Solar Cool White (37) for shade and heat control, plus a Clear Diffuse version that scatters light into the canopy.

ACRYLITE Alltop is the same 16 mm sheet with ribs 64 mm (2 1/2 inches) apart, so less rib shadow and more light: 89 percent in the UV-absorbing version and 91 percent in the UV-transmitting one. The UV-transmitting sheet exists for growers who want the full solar spectrum, which the maker says increases growth and quality in certain crops and reduces the need for supplemental UV. Alltop carries the NO DRIP coating on both sides and runs to 28 feet long. Both versions carry the same insulation, R-2.04 and U-0.49.

For comparison, the same distributor's 16 mm triple-wall polycarbonate transmits 76 percent, and the Alltop literature quotes 72 percent for 16 mm polycarbonate. Ten to fifteen points of light is a real difference in a winter greenhouse.

The warranty

This is the argument for acrylic in one paragraph. ACRYLITE's warranties are non-prorated and full replacement: 30 years against yellowing on colorless sheet, 10 years on light transmission, and 10 years on hail. Acrylic is UV-stable as a material rather than by a coating, which is why the maker can promise the sheet will not yellow, go brittle, or lose light, and why a scratch through the surface does not start the degradation that a scratched polycarbonate cap layer does. The University of Arkansas greenhouse program puts acrylic bi-wall at a 20 to 25 year life with minimal light loss over ten years.

NO DRIP and condensation

Every greenhouse sweats. On plain glazing the condensation forms droplets that scatter light and rain on the benches, which is how algae and fungus get started. The patented NO DRIP coating makes water spread into a continuous film that runs to the gutter instead. On Resist it is on one side; on Alltop, both. The coating ships under a protective layer that has to be washed off with water and a sponge, or hosed down, to activate it, and it is the reason to leave the film on until the panel is installed.

Weight, stiffness, and movement

The 16 mm sheet weighs 0.9 to 1 pound per square foot, against about 0.55 for 16 mm polycarbonate. In return it is stiff: supported on all sides at 1200 mm wide, a 16 mm sheet needs no intermediate cross members for uniformly distributed loads up to 15.7 pounds per square foot. The 8 mm needs supports every 106 inches. Fewer purlins means less shadow.

The number that ruins acrylic roofs is 6 mm per metre, or 1/16 inch per foot: how much the sheet moves with heat and moisture. A 16-foot panel grows and shrinks a full inch. The maker's installation guidelines and the aluminum bar-and-gasket systems sold for the sheet allow for it. Screws through the sheet into wood battens do not, and the sheet cracks at the hole. Maximum service temperature is 160°F, so a black-painted bar in full sun is another thing to avoid.

Fire

Acrylic burns. ACRYLITE is rated C2 or CC2 under ASTM D-635, under 150 flame spread on CAN/ULC S102.2, and B2 under DIN 4102, with a self-ignition temperature of 830°F and low smoke. The maker's own precaution sheet says it burns rapidly to completion if not extinguished. Building codes classify it as a CC2 light-transmitting plastic with area limits, and our acrylic vs glass guide explains the classes. Polycarbonate is CC1 and far less flammable, and that is the one argument for it that acrylic cannot answer.

Price and buying

Greenhouse Megastore lists 16 mm clear from $1,225 in five- and ten-panel bundles, 47 1/4 inches wide in lengths from 6 to 16 feet, and 8 mm from $745. Both were sold out when we checked, which is normal in season; order in late winter. Delivery is by motor freight with a truck that needs up to 70 feet of access and someone on site to unload. Custom cut lengths are available to 28 feet, and the Evonik-era catalog listed a $300 repacking charge for custom orders under 20 sheets, with special-order lengths non-returnable.

The polycarbonate on the same shelf starts at $685 a bundle. The premium buys light, a warranty polycarbonate does not offer, and a roof that looks the same in year fifteen.

Who should buy it

Growers and hobbyists who heat through winter, who plan to keep the structure, and whose frame can carry a pound per square foot. Choose Resist if you want UV blocking and a shade color option; choose Alltop if light transmission is the priority. For an unheated house, a roof over a shade structure, or a tighter budget, the corrugated single-skin ACRYLITE panel has the same warranty and 90 percent light with no insulation.

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