FFA Floriculture Practice Test

Which glazing material for greenhouses allows the lowest light transmittance?

1. Glass

2. Single-layer polycarbonate

3. Double-layer polyethylene

4. Acrylic

The correct answer is: Double-layer polyethylene

Single-layer polyethylene is a widely used glazing material for greenhouses, but it tends to have a variable light transmittance depending on factors such as thickness, color, and age. While it is known for its excellent insulation properties and affordability compared to other materials, it does not necessarily provide the highest light transmittance. Double-layer polyethylene is designed to provide more insulation than a single layer. The air-filled space between the two layers enhances thermal performance, but this design also reduces the amount of light that can penetrate compared to other glazing types. Thus, it allows the lowest light transmittance among the given options. Other glazing materials like glass, single-layer polycarbonate, and acrylic usually allow for greater light transmittance. Glass, for instance, is known for its high clarity and durability, whereas polycarbonate and acrylic provide a balance of light transmittance and insulation but still allow more light than double-layer polyethylene.