Polycarbonate vs glass: the side-by-side
Published figures vary by brand and test method, so we show the source for each row. Light transmission is for clear panels.
| Glazing | Light transmission | U-value (Btu/hr·sf·°F) | R-value | Hail behavior | Lifespan / UV | Relative cost |
|---|---|---|---|---|---|---|
| Poly film, single layer | 85–88% | 1.1–1.2 | ~0.83–0.91 | Tears or punctures; cheap to replace | 1–4 years (UArk, Rutgers) | Lowest |
| Poly film, double layer (inflated) | 77–88% | 0.70 | ~1.43 | Same as single | 1–4 years | Low |
| Twin-wall polycarbonate, 6 mm | 80% | 0.61 | 1.64 | Flexes rather than shatters | 10-year limited warranty (Gothic Arch) | Moderate |
| Twin-wall polycarbonate, 8 mm | 80–81% | 0.56–0.58 | 1.64–1.72 | Flexes; warranties cover hail only up to a set stone size | 10-year warranty; 20+ years cited (UArk) | ~$2.62/sf, panels only |
| Triple-wall polycarbonate, 16 mm | 74% | 0.40 | 2.50 | Stiffer; thicker outer skin | 10-year limited warranty (Gothic Arch) | ~$5.72/sf, panels only |
| Five-wall polycarbonate, 16 mm | 65–73% | 0.438 | 2.61–2.78 | Stiffest multiwall option | 10-year pro-rated warranty incl. hail (Growing Spaces) | Similar to triple-wall |
| Single tempered glass | ~90% | 1.05–1.1 | ~0.91–0.95 | Can break under large hail | 25–30+ years if unbroken | ~$2.50–$3.50/sf, panels only (HomeGuide); heavier frame |
| Double-pane (insulated) glass | 78–90% | 0.70 | ~1.43 | Can break under large hail | 25–30+ years if unbroken | Highest; priced per project |
Sources for glass and film rows: University of Arkansas and Rutgers NJAES (A.J. Both, 2008). Five-wall figures differ between makers: Gothic Arch lists 73% and R-2.61; Growing Spaces lists 65% and R-2.778.
Panel prices are published prices as of Oct 2026, panels only, no framing, fasteners or labor: 8 mm clear twin-wall at $83.78 per 4 × 8 ft sheet from Polycarbonate Store ($83.78 ÷ 32 sf ≈ $2.62/sf), and 16 mm clear triple-wall at $915 for five 48 in × 8 ft panels from Greenhouse Megastore ($915 ÷ 160 sf ≈ $5.72/sf; listed sold out at the time). Broader cost guides list glazing materials at $1.50–$3.00/sf for polycarbonate and $2.50–$3.50/sf for glass, and put labor at about 40% of a greenhouse's total cost (HomeGuide). Installed cost for your build depends on framing, size and site.
How much heat does each glazing lose in a Wichita winter?
Heat loss through glazing is roughly area × U-value × heating degree days × 24 hours. Wichita averages 4,592 heating degree days a year, with 986 in January (NOAA NCEI 1991–2020 normals).
For a greenhouse with 500 sq ft of glazing surface (roof, walls and gables combined):
| Glazing | U-value used | January loss | Annual loss |
|---|---|---|---|
| Single glass / single film | 1.1 | 13.0 million Btu | 60.6 million Btu |
| Double-pane glass / double film | 0.70 | 8.3 million Btu | 38.6 million Btu |
| 6 mm twin-wall | 0.61 | 7.2 million Btu | 33.6 million Btu |
| 8 mm twin-wall | 0.58 | 6.9 million Btu | 32.0 million Btu |
| 16 mm triple-wall | 0.40 | 4.7 million Btu | 22.0 million Btu |
Worked example for 8 mm twin-wall in January: 500 × 0.58 × 986 × 24 = 6,862,560 Btu. One therm is 100,000 Btu, so that's about 69 therms of heat lost through the glazing in an average January.
This is conduction only, at a 65°F base, before air leakage and solar gain. Your actual setpoint changes the number. The ranking doesn't change: going from single glass to 16 mm triple-wall cuts glazing heat loss by about 64%. Our one-winter heating guide turns these Btu into fuel cost with dated Kansas rates.
When polycarbonate is the right call
- You want to grow through the winter. The insulation gap is large, and it compounds every heating month.
- You can't watch the sky. Polycarbonate flexes instead of shattering, so a hailstorm you slept through is less likely to mean a broken roof.
- You want diffused light. Multiwall panels scatter light, which reaches lower leaves and reduces hot spots (Growing Spaces).
- You want a lighter frame. A 16 mm multiwall panel weighs a fraction of the same area of glass, which simplifies framing and foundations.
The trade-offs are real. Polycarbonate loses some light over time, scratches more easily than glass, and its warranties run about 10 years. Read the warranty before you buy — the hail coverage is narrower than "hail resistant" suggests. Our hail guide quotes the actual terms.
When glass is the right call
- Light is your limiting factor. Glass transmits around 90% of light, versus about 74–81% for most clear multiwall polycarbonate.
- Clarity matters. For a conservatory or a greenhouse you look through, nothing else compares.
- You plan for decades. Glass doesn't yellow, and glass greenhouses commonly last 25–30+ years if the panes survive.
- You have a hail plan. That could be a hail screen, a removable storm-season cover, or simply budgeting for replacement panes.
Single glass is the poorest insulator on this list. If you want glass and winter growing, plan for double-pane glass or a larger heating budget.
What about poly film?
Film is the right answer for many hoop houses and high tunnels. It's the cheapest covering, it goes on fast, and a torn sheet is a weekend fix rather than a structural repair. Double-layer inflated film matches double-pane glass on U-value (0.70). The cost is replacement every few years, as UV breaks the film down. See our high tunnel installation page for film-covered structures.
How we install glazing for Wichita conditions
The panel is only part of the system. How it's held in place decides how it handles wind and hail.
- UV side out. Polygal's warranty, for example, requires the UV-protected side to face outward (Polygal warranty). Install it backward and both the panel and the warranty fail.
- Flutes vertical, ends sealed. Multiwall channels run with the slope so condensation drains. Ends are taped and capped to keep out dust and insects.
- Room to expand. Polycarbonate grows and shrinks with temperature. We leave clearance in the profiles so panels don't bow or pop in July.
- Tight purlin spacing on roofs. Closer supports mean less panel flex under wind, snow and hail.
- Wind-rated fastening. Fastener type and spacing follow the panel maker's guidance and the design wind load — see our wind-rated design guide.
We'll tell you which panel lines fit your budget and hail exposure when we quote. Warranty terms are written into your quote; ask for workmanship and material coverage in writing.
Glazing is one decision among several in a custom build. Our custom greenhouse construction page shows how it fits with footprint, foundation and anchoring. If you're designing around winter sun, see the passive solar greenhouse page — glazing choice changes how much stored heat you keep overnight.
Frequently asked questions
Is polycarbonate or glass better for a greenhouse in Kansas?
For most Kansas greenhouses, multiwall polycarbonate. It insulates better than single glass and survives most hail. Glass is better when maximum light, clarity and long life outweigh hail risk and heating cost.
How much light does twin-wall polycarbonate let through?
Clear twin-wall panels are typically listed at about 80–81% light transmission. Clear 16 mm triple-wall is around 74%, and five-wall 65–73% depending on the maker.
Does polycarbonate really insulate better than glass?
Yes. Single glass has a U-value around 1.05–1.1. 8 mm twin-wall is about 0.58 and 16 mm triple-wall about 0.40. In Wichita's climate that's roughly 32 million vs 61 million Btu a year through 500 sq ft of glazing.
How long does polycarbonate greenhouse glazing last?
Manufacturer warranties are usually 10 years. Some sources cite 20+ years of service. Expect gradual light loss over time; warranties typically cap that loss at around 6–10% over the warranty period.
Is tempered glass hail-proof?
No. Glass can break under large hail. If you choose glass in Sedgwick County, plan for protection or replacement. The hail guide covers options.
What does polycarbonate glazing cost?
Published panel prices in Oct 2026 run about $2.62/sq ft for 8 mm twin-wall and about $5.72/sq ft for 16 mm triple-wall, panels only. National cost guides list glass at about $2.50–$3.50/sq ft, materials only (HomeGuide). Installed cost depends on framing, size and site.
Get a quote
Tell us what you want to grow, how you plan to heat it and where it will sit. We'll recommend a glazing and frame combination for your site and quote it.