Glass vs Polycarbonate Greenhouse: The Honest Answer

If you've been researching greenhouses for more than ten minutes, you've already hit this question. Glass or polycarbonate? Everyone has an opinion. Most of those opinions are incomplete.

Here's the honest answer — with no agenda.

What actually matters

Both materials work. Both let plants grow. The difference comes down to four things: light, insulation, durability, and aesthetics.

Light transmission

Glass wins. Premium tempered glass transmits close to 100% of available light. High-quality twin-wall polycarbonate transmits around 88%.

That 12% gap sounds small. For most crops — lettuce, herbs, spinach, kale — it doesn't matter at all. For high-light crops like tomatoes and peppers grown in northern climates with short winter days, every percentage point counts.

Insulation

Polycarbonate wins — specifically twin-wall and triple-wall panels. The air pockets between the layers act as insulation. A quality 6mm twin-wall polycarbonate panel insulates noticeably better than a single-pane glass panel.

This matters most if you're trying to keep heating costs down in a cold climate.

Durability

Tempered glass is extremely strong — it handles wind, snow load, and hail well. Quality tempered glass lasts 15-20 years without degradation.

Polycarbonate is impact-resistant and bends rather than shatters. The downside: UV exposure causes panels to yellow over time. Quality panels with proper UV coating last 10+ years. Always check the UV warranty before buying.

Aesthetics

Glass wins clearly. A glass greenhouse looks permanent, architectural, and beautiful. It becomes a feature of your garden rather than something you tolerate in it.

The honest recommendation

• Choose glass if: aesthetics matter, you want maximum light, and you're building something permanent.
• Choose polycarbonate if: you're in a very cold climate where insulation is the priority, or budget is a significant factor.

Both are good. The worst choice is cheap polycarbonate with no UV warranty — panels that yellow and crack after three years.

What ZenGreenhouses offers

We carry both. Our modular polycarbonate greenhouses use 4mm and 6mm twin-wall panels from Polish manufacturers — the same factories that supply commercial growers across Europe. Our Aurora Nordic Glass Room uses premium 4mm tempered safety glass with an aluminum frame engineered to European standards.

Both come with free US shipping and a 10-year structural warranty. Questions? Email us at shop@zengreenhouses.com