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Glass vs Polycarbonate Greenhouses: Which is Better for Your Growing Needs?

Glass vs Polycarbonate Greenhouses: Which is Better for Your Growing Needs?

One of the most important decisions for gardeners and greenhouse growers is choosing between a glass or polycarbonate greenhouse. Both materials have advantages and disadvantages when it comes to factors like durability, insulation, light transmission, and cost. By understanding the key differences between polycarbonate and glass glazing, you can determine which is better suited for your climate, budget, and growing needs.

a photo comparison between a glass and polycarbonate greenhouse

Key Differences Between Polycarbonate and Glass Greenhouse Glazing

When evaluating polycarbonate versus glass greenhouses, there are a few major factors that set these two materials apart:

Light Transmission and Diffusion

Light transmission is an important consideration for any greenhouse. Plants need adequate sunlight to grow and thrive.

Polycarbonate panels and sheets diffuse incoming light, spreading it evenly across the greenhouse. This prevents hot spots and promotes uniform growth. Glass transmits more direct light than polycarbonate. For gardeners prioritizing maximum light transmission, glass is the better option.

According to greenhouse glazing experts, glass transmits around 90% of available light, while polycarbonate panels transmit around 70-83% depending on thickness. For greenhouse growers wanting the brightest, sunniest growing environment possible, glass may be preferable.

Durability and Impact Resistance

Durability is another key factor when choosing a greenhouse glazing material. Polycarbonate is incredibly impact-resistant and shatterproof, making it a very durable glazing option.

Polycarbonate’s high strength-to-weight ratio makes it 200 times stronger than glass and 30 times stronger than acrylic. Polycarbonate glazing can withstand hail, falling branches, and other impacts that would shatter traditional glass. This durability makes polycarbonate a smart choice for greenhouses in areas prone to severe weather events.

While glass is strong, it cannot match the impact resistance of polycarbonate. Any impact that does cause the glass to break will likely require full pane replacement, while polycarbonate sheets can better withstand fractures and cracks.

Insulation and Temperature Regulation

A greenhouse’s ability to maintain stable internal temperatures is dependent on the glazing material’s insulating properties.

Polycarbonate inherently provides better insulation than glass. The layered structure of polycarbonate traps air pockets, slowing heat transfer. Glass greenhouses are prone to greater temperature fluctuations, especially rapid cooling at night.

Industry testing reveals that polycarbonate sheets provide R-values around 1.54 per inch, while standard single-pane glass with 6mm thickness offers an R-value of about 0.16. The higher R-value of polycarbonate translates to better thermal efficiency and reduced heating costs during colder weather.

Safety and Security

Safety is another consideration when choosing between glass or polycarbonate greenhouses. Polycarbonate is inherently shatterproof, making it a safer choice if you have children or pets that will be interacting with the structure.

Polycarbonate’s strength also makes it very difficult to break through, providing enhanced security. Glass is easier to break than polycarbonate, but laminated, tempered safety glass can also be used in greenhouses to improve security.

Costs and Maintenance

When evaluating the costs of polycarbonate versus glass greenhouses, you must consider both upfront expenses and long-term maintenance.

Polycarbonate glazing materials cost significantly less upfront compared to glass. Polycarbonate panels cost around $0.12 per square foot while glass can cost $2 to $2.50 per square foot. However, polycarbonate lasts just 10-25 years compared to glass’s 40-50 years lifespan.

While glass has a higher upfront cost, it may save money over decades of use compared to replacing polycarbonate panels every 10 years. Consider your budget, timeline, and projected maintenance costs when factoring in expenses. Routine cleaning and upkeep will also impact long-term costs.

an actual product image of the Hoklartherm Riga Greenhouses 5

Advantages and Disadvantages of Polycarbonate Greenhouses

To determine if a polycarbonate or glass greenhouse is best for your needs, carefully weigh the unique pros and cons of each material:

Pros of Polycarbonate Glazing

  • Extremely durable and impact-resistant
  • Provides UV protection
  • Excellent thermal insulation properties
  • Lightweight compared to glass
  • Lower upfront costs
  • Light diffusion creates a uniform growing environment

Cons of Polycarbonate Glazing

  • Can discolor and degrade over time
  • Needs replacement every 8-10 years
  • Not biodegradable or recyclable
  • Toxic fumes if burned
  • Less light transmission than glass

Advantages and Disadvantages of Glass Greenhouses

Pros of Glass Glazing

  • Transmits more natural sunlight
  • Won't degrade or discolor
  • Long lifespan of 30-50 years
  • Recyclable and environmentally inert
  • Withstands flames/fire

Cons of Glass Glazing

  • Vulnerable to breakage from hail, debris
  • Requires extensive framing and foundation
  • Weaker thermal insulation
  • Higher heating costs
  • Heavy and difficult to transport

When weighing the pros and cons, polycarbonate excels in durability, insulation, and cost, while glass maximizes sunlight and offers a longer-lasting clear surface. Determine which factors are most important for your needs.

Comparing Polycarbonate and Glass Greenhouses for Environmental Impact

Many greenhouse growers also consider the environmental impacts of different glazing materials. Here's how polycarbonate and glass compare:

Manufacturing and Disposal

Polycarbonate is manufactured from petroleum-based chemicals, so it has a larger carbon footprint than glass. Standard polycarbonate panels also cannot be recycled, and release toxic BPA and fumes when incinerated, making disposal an environmental issue.

Glass is made from abundant natural materials like sand, limestone, and soda ash. It's recyclable and relatively inert in landfill conditions. However, transporting heavy glass does burn more fossil fuels. Overall, glass is considered a greener material.

Energy Efficiency in Use

Once in use, polycarbonate offers better thermal insulation and energy efficiency than glass. The layered structure creates air gaps that reduce conductive heat transfer. Polycarbonate’s higher R-value and lower U-factor decrease heating costs during cold weather.

Well-insulated glass greenhouses can perform similarly to polycarbonate but require using double-pane or triple-pane glass, often with expensive specialized low-E coatings. This further drives up glass greenhouse costs.

For energy efficiency while in use, polycarbonate is the better choice. But manufacturing and disposal differences make glass the more sustainable option overall.

a side by side photo of polycarbonate and glass sheets

Choosing the Best Glazing Material for Your Greenhouse

Determining whether a polycarbonate or glass greenhouse is right for you depends on several factors:

Consider Your Climate and Growing Goals

If you live in a region with cold winters and need to maximize heat retention, polycarbonate's insulating properties provide an advantage. Polycarbonate is also ideal for high-altitude greenhouses.

If you prioritize growing produce and flowers that demand peak sunlight and heat, glass may better meet your needs. For hobby greenhouses focused on recreational use rather than maximizing yields, polycarbonate is often sufficient.

Evaluate Your Budget and Quality

Polycarbonate panels offer big upfront savings but need replacement every 10 years. For hobby or temporary greenhouses, polycarbonate's low initial cost may outweigh lifespan considerations.

For commercial operations or more permanent structures, the higher upfront cost of glass pays dividends over decades of reliable performance. Glass can also increase resale value down the road.

Prioritize Key Qualities Like Durability, Insulation, and Light Transmission

If your region experiences severe weather like hail or heavy snow loads, polycarbonate’s impact resistance provides critical protection. For glass greenhouses in these environments, laminated safety glass is recommended.

If you want to extend your growing season and need maximum insulation, polycarbonate also excels in cold weather climates. For the brightest light transmission, glass remains the best option.

an actual image of the Exaco Janssens Royal Victorian VI Greenhouse VI 23 surrounded by plants

Final Recommendations on Polycarbonate vs Glass Greenhouses

When weighing all factors, here are some final recommendations on choosing polycarbonate or glass:

  • For hobby greenhouses in temperate climates, polycarbonate often provides the best combination of affordability, durability, and functionality.

  • In cold climates, polycarbonate’s superior insulation offers big advantages for heating efficiency and expanding the growing season.

  • For permanent commercial greenhouses focused on maximizing yields, glass is worth the higher investment for peak light transmission and decades of unbeatable clarity.

  • In regions with heavy snow, hailstorms, or cold winters, polycarbonate is very difficult to beat in terms of both economics and protective qualities.

  • For environmentally-conscious growers, glass is the more sustainable choice, while polycarbonate provides better energy efficiency in use.

Here is a quick rundown of recommended materials for different types of greenhouse:

Type of Greenhouse Recommended Material
Hobby greenhouse Polycarbonate
Cold climate Polycarbonate
Commercial greenhouse Glass
Severe weather region Polycarbonate
Environmentally friendly Glass
Hoklartherm Greenhouse 14' x 23' door and windows opened


When weighing all the factors, it is clear that polycarbonate is the best glazing choice for most hobby greenhouses. Its durability, insulation, and affordability are unbeatable compared to glass. While glass offers maximum light transmission, polycarbonate diffusion still provides ample light for small-scale growing. For the average grower looking to extend the season on a budget, polycarbonate is hands down the ideal glazing material for hobby greenhouses. Its strengths make it superior to glass for most temperate backyard growing needs.


Is handling larger glass panes difficult when building a greenhouse?

Yes, handling larger glass panes can be difficult when building a greenhouse. This is why it could be a benefit to go for polycarbonate, as the material is lightweight and easy to handle. Also, polycarbonate is made up of two sheets of film put together with space in between, making it much safer to handle than glass.

Are there any special requirements that polycarbonate needs for maintenance?

Generally, polycarbonate needs regular cleaning with a mild detergent and water to maintain its clarity. Also, make sure that the polycarbonate is treated with UV protectants to prevent yellowing over time. Polycarbonate definitely has fewer maintenance requirements compared to regular glass panels.

Can you use old windows instead of standard glass or polycarbonate for a greenhouse?

Yes, you can build a greenhouse from reclaimed glass panels or old windows. Although this is a sustainable and cheaper option, it may not offer the same level of durability and  UV protection as a greenhouse made from specially designed polycarbonate greenhouse glazing or horticultural glass. Always consider the quality of the material and its suitability for your specific climate and plant requirements.

What is the best greenhouse covering?

The best greenhouse covering largely depends on individual gardening needs and expectations. This includes considering factors such as cost, durability, heat retention, and light transmission. If durability and heat retention are your paramount priorities, go for polycarbonate. However, if prefer visual appeal and are willing to invest time and resources into maintenance, glass could be your best option.

What should I be wary of when choosing between glass and polycarbonate greenhouse kits?

When considering glass and polycarbonate options for greenhouse kits, be wary of the following points: Consider how much time and effort you're willing to invest in installation and consider the weather conditions in your location. Furthermore, bear in mind the type of plants you are growing.

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About The Author

Andy Wu - Resident Expert

Andy Wu - Resident Expert

Andy Wu is the resident backyard products expert and hails from Atlanta, Georgia. His passion for crafting outdoor retreats began in 2003.

As a fellow homeowner, he founded Backyard Oasis to provide top-quality furnishings and equipment, collaborating with leading manufacturers.

His main focus is on sheds and generators!

In his spare time he like to hike the tallest mountains in the world and travel with his family.

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