Polycarbonate Panel Thickness Guide for Greenhouse Coverings

Greenhouse gardening in a colder climate can be challenging. Properly covering your greenhouse is crucial in maintaining a climate-controlled environment. Polycarbonate is a popular material for greenhouse coverings because it’s lightweight, durable, and has excellent light transmission properties. However, polycarbonate panels come in various thicknesses, affecting several essential aspects of greenhouse performance, such as heat retention and durability.

Understanding Thermal Performance: U-Values and R-Values

The thermal performance of any greenhouse covering material is measured using two key metrics that work inversely to each other:

U-Values: Heat Loss Rate

The thermal performance of a material, in terms of the rate of heat loss, is commonly expressed as a U-value. The better insulated a structure is, the lower the U-value will be. So, lower numbers equal better performance. This measurement is crucial for determining how much energy you’ll need to maintain optimal growing temperatures in your greenhouse.

R-Values: Thermal Resistance

Inversely, the measurement of thermal resistance a material has is expressed as the R-value. The higher the number, the better it insulates, which means less cost in heating and cooling your greenhouse and better protection for your plants. R-values directly correlate with energy savings and plant protection during extreme weather conditions.

Thicker polycarbonate panels provide superior thermal resistance, reducing heat loss and energy costs.

Polycarbonate Panel Thickness Comparison

When comparing the panel thickness of different brands, Grandio Greenhouses® uses some of the thickest panels in the hobby greenhouse industry. Most hobby greenhouse manufacturers use solid or twin-wall polycarbonate that is 4mm or less. Grandio Greenhouses® uses 10mm twin-wall polycarbonate panels on most of their models, except for the Ascent which has 6mm twin-wall panels. That’s over two times thicker than many competitors.

What This Thickness Difference Means

So what does this all mean? The thicker the panels, the better they are at keeping heat in. This translates to several practical benefits for greenhouse gardeners:

• Reduced heating costs – Better insulation means your heating system works less to maintain optimal temperatures
• More stable growing environment – Thicker panels reduce temperature fluctuations that can stress plants
• Extended growing season – Superior insulation allows for earlier spring starts and later fall harvests
• Better plant protection – Consistent temperatures protect sensitive plants from temperature shock

Strength and Durability Benefits

Another significant benefit of thicker panels is strength and durability. Polycarbonate is known for its incredible impact resistance and rigidity. The thicker the sheet, the more rigid it becomes. If high winds or snow are a concern, you will want to consider a 6mm panel or thicker.

Weather Resistance

Thicker polycarbonate panels offer superior protection against various weather conditions:

• Wind resistance – Increased rigidity reduces panel flexing and potential damage
• Snow load capacity – Thicker panels can support heavier snow accumulation without sagging or breaking
• Hail protection – Enhanced impact resistance protects against hail damage
• UV degradation resistance – Thicker panels maintain structural integrity longer under UV exposure

Thicker polycarbonate panels provide superior snow load capacity and weather resistance.

Structural Reinforcement

Not only will the thicker panel reinforce the frame, but it will also increase the snow load capacity of the greenhouse and reduce the risk of breakage. This structural support is particularly important in regions that experience:

• Heavy snow accumulation during winter months
• Strong winds or frequent storms
• Extreme temperature variations
• Hailstorms or severe weather events

Light Transmission and Plant Growth

While thermal performance and durability are crucial, light transmission remains essential for plant growth. Fortunately, modern polycarbonate panels maintain excellent light transmission even at greater thicknesses:

Light Transmission Rates

• 4mm twin-wall: 80-82% light transmission
• 6mm twin-wall: 78-80% light transmission
• 10mm twin-wall: 75-77% light transmission

The slight reduction in light transmission with thicker panels is offset by the improved growing environment and extended season capabilities they provide.

Cost-Benefit Analysis

While thicker polycarbonate panels require a higher initial investment, the long-term benefits often justify the cost:

Initial Investment vs. Long-term Savings

• Energy savings – Reduced heating and cooling costs over the greenhouse lifetime
• Durability – Longer panel lifespan reduces replacement costs
• Plant protection – Better growing conditions lead to higher yields and healthier plants
• Season extension – Extended growing season increases productive months per year

Installation and Maintenance Considerations

Thicker polycarbonate panels require slightly different installation approaches but offer maintenance advantages:

Installation Tips

• Use appropriate fasteners designed for the specific panel thickness
• Allow for thermal expansion with proper spacing
• Ensure adequate support structure for the increased panel weight
• Follow manufacturer guidelines for sealing and weatherproofing

Maintenance Benefits

• Reduced frequency of panel replacement
• Better resistance to stress cracking
• Less likelihood of weather-related damage
• Improved seal integrity over time