Which is cheaper, glass or polycarbonate greenhouse?

Polycarbonate is cheaper up front on panels and the lighter frame it needs, and it saves on heating. Glass costs more and needs a stronger structure but lasts far longer, so over 25 years the math narrows. For most backyard budgets, polycarbonate is lower cost.

Polycarbonate vs Glass Greenhouse: Heat Loss, Cost, Lifespan

Q: Is polycarbonate warmer than glass in a greenhouse?

Twin-wall polycarbonate is, with an R-value of roughly 1.6-2.0 versus single glass near 0.9, losing close to half as much heat through the glazing. That means lower winter heating costs, the main reason cold-climate growers choose it despite glass passing more light.

Q: Can hail break a polycarbonate greenhouse?

Very unlikely. Polycarbonate is roughly 200 times more impact-resistant than glass. Severe hail may dimple or scratch it but it does not shatter into a hazard the way glass does, a decisive advantage in storm-prone regions.

Updated July 2026 · Editorial team · Topic: greenhouses / materials

Polycarbonate vs Glass Greenhouse: Heat Loss, Cost, Lifespan — Greenhouses

A hailstorm settles the argument faster than any spec sheet. Two identical greenhouses, one glazed in glass, one in twin-wall polycarbonate, take the same barrage of golf-ball ice. The glass house is a bill and a broom. The polycarbonate one has a few dimples and keeps working. That single afternoon is why the material debate is not really about clarity or looks — it is about which failure mode you would rather live with, and how many winters of heating bills you are signing up for.

Short answer: Twin-wall polycarbonate insulates better and survives impact; glass looks better and lasts longer. Single-pane glass has an R-value near 0.9 and twin-wall polycarbonate around 1.6–2.0 — meaning the poly loses roughly 40–50% less heat, a real number on a winter power bill. Glass transmits about 90% of light versus poly's ~80%, and glass lasts 25+ years to polycarbonate's 10–15 before UV haze sets in. For most backyard growers who heat in winter, twin-wall wins; for a permanent showpiece, glass does.

Reviewed by the BackyardStead Lab editorial team. We publish real ROI, plain numbers and USDA/extension data so you can judge for yourself — we run the math, not a farm. Educational information only: backyard-chicken and livestock rules vary by city, home canning must follow USDA/NCHFP-tested methods (botulism risk), and mushrooms should be grown only from a known-species kit — never foraged on our word.

The four numbers that decide it

Ignore the brochure adjectives. Four measurable properties separate these materials, and every trade-off flows from them.

Property	Single-pane glass	Twin-wall polycarbonate
Insulation (R-value)	~0.9	~1.6–2.0 (4–8 mm)
Light transmission	~90%, clear/direct	~80%, diffused
Lifespan	25+ years	10–15 years
Impact resistance	Shatters	~200× glass; near-unbreakable
Weight / frame needs	Heavy; strong frame + foundation	Light; simpler frame
Panel cost	Higher	Lower

Heat loss is where the money actually is

The R-value gap sounds abstract until it becomes a heating bill. Heat escapes a greenhouse in rough proportion to the surface area divided by the R-value, so twin-wall's roughly doubled R-value cuts conductive heat loss through the glazing by around 40–50% compared with single glass. For a small heated greenhouse in a cold zone, that difference can be tens of dollars a month in electricity through the depth of winter — poly's insulation quietly pays back part of its own cost every January.

There is a subtlety: the light poly transmits is diffused rather than direct. That scatters light around the interior, reaching lower leaves and reducing scorch and shadow, which many growers consider a horticultural plus even though the headline transmission number is lower. Glass delivers more total light but in hard, direct beams that can burn foliage pressed against the pane.

Field note: Polycarbonate's lifespan hinges entirely on which side faces the sun. Twin-wall sheets have a UV-protective coating on one face only, and every sheet is printed to show which side goes out. Install a panel upside down — coating inward — and the sun eats the unprotected side, yellowing and clouding it in a few seasons instead of a decade. The most common way people "prove" polycarbonate is short-lived is by mounting it backwards.

What each material is genuinely best at

We have not watched a glass pane and a polycarbonate sheet weather side by side in our own yard across ten winters — the figures here come from manufacturer data and extension studies, which is the only honest source short of a decade-long trial. The strengths sort cleanly:

Twin-wall polycarbonate wins on: insulation, heating cost, impact and hail resistance, safety (no shattering near kids or pets), lighter frames, and lower panel price. It is the practical grower's material.
Glass wins on: light clarity, appearance, scratch resistance, decades of service, and not clouding with age. It is the material for a permanent, heated, showpiece greenhouse.
Single-wall polycarbonate is the budget floor — cheap and shatterproof but insulating little better than glass, so it belongs on entry kits, not cold-climate winter growing.

Where these materials show up across price tiers is mapped in the greenhouse kit buying guide.

Common mistakes

Buying single-wall thinking it is "polycarbonate." Single-wall poly insulates like a window; only twin- or triple-wall gives the insulation advantage that makes polycarbonate worth choosing for winter.
Installing twin-wall upside down. The UV coating faces the sun or the panel dies early. Check the printed film before you fasten anything.
Choosing glass in hail or ball-game country. A single storm or stray throw turns a glass greenhouse into a repair project. Impact resistance is not a footnote if your climate throws ice.
Ignoring the frame and foundation glass demands. Glass is heavy and needs a strong frame on a real foundation. Budgeting for the glass but not the structure under it is how projects stall.
Sealing twin-wall channel ends open. The hollow channels must be taped and capped, or they fill with dust, algae, and condensation that cloud the panel from the inside.

FAQ

Is polycarbonate warmer than glass in a greenhouse?

Twin-wall polycarbonate is, yes — its R-value of roughly 1.6–2.0 versus single glass at about 0.9 means it loses close to half as much heat through the glazing. That translates to noticeably lower winter heating costs, which is the main reason cold-climate growers pick it over glass despite glass transmitting more light.

Does polycarbonate turn yellow over time?

Quality twin-wall with an intact UV coating resists yellowing for 10–15 years; cheap or improperly installed sheets cloud faster. The single biggest cause of early yellowing is mounting the panel with the coated side inward, so it is often an installation error rather than a flaw in the material itself.

Which is cheaper, glass or polycarbonate?

Polycarbonate is cheaper up front on both panels and the lighter frame it needs, and it saves on heating over its life. Glass costs more initially and demands a stronger structure, but it lasts far longer, so over 25 years the lifetime math narrows. For most backyard budgets, polycarbonate is the lower-cost choice.

Can hail break a polycarbonate greenhouse?

It is extremely unlikely — polycarbonate is roughly 200 times more impact-resistant than glass and is the same family of material used in riot shields. Severe hail may dimple or scratch it, but it does not shatter into a hazard the way glass does, which is a decisive advantage in storm-prone regions.

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General educational information, not professional horticultural advice. Prices, energy costs, plant hardiness and local climate vary by region and season; check figures against current listings and your local extension office before spending.