A greenhouse allows you to grow plants that you would otherwise not be able to grow under certain circumstances. The warmth inside a greenhouse will protect plants from cold external temperatures while providing the ideal conditions for them to grow and thrive.
A greenhouse cannot have a solid roof as it will block out the light and heat required by the plants inside the greenhouse to survive. Many different roofing materials are available for your greenhouse, but the roof should always be made from light-permeable materials.
Greenhouses come in many different designs and are constructed from many different materials. A greenhouse roof is crucial to the overall design and can mean success or failure for any of the plants growing inside the greenhouse.
Should A Greenhouse Have A Solid Roof?
A greenhouse cannot have a solid roof as it needs to let light in to transmit to the plants inside the structure. All greenhouse roofing materials must be a transparent or semi-clear, light-permeable material.
As the sun travels across the sky, more direct sunlight is fed into the greenhouse through the roof than through the sides, even if the same material is used on the sides and the roof of the structure.
The incoming solar radiation from the sun warms the soil, plants, and anything else inside the greenhouse. As the greenhouse heats up, the heat is retained, creating an ideal environment to grow plants, vegetables, and fruit.
The Pros And Cons Of A Solid Roof On A Greenhouse
Many materials are used as roofing on greenhouses. When deciding on which materials to use, you should consider which type of greenhouse is to be built and what the budget is.
Different materials are suited to different sized greenhouses, so consider the kind of framing materials to be used and decide whether the structure is permanent, semi-permanent, or mobile. This will also affect the choice of materials.
Planning your greenhouse first and deciding where it will stand in your garden can determine the choice of materials required for the roof. For example, if the greenhouse will be in full sun all day, you might want to use a lighter roofing material, whereas if it is in a partly-shaded area, you may need to use a more robust material to retain more heat.
Here’s a video showing some of the popular greenhouse roof materials, with more info below:
Let’s take a look at the different materials and discuss their pro and cons.
Traditionally, greenhouses were constructed entirely of glass. Glass is a permanent solution for any greenhouse and can be long-lasting if installed correctly. It is the most transparent, most light-permeable material available on the market.
Pros Of Using Glass Roofing On A Greenhouse
- Tempered glass is five times thicker than regular glass and poses the least risk of shattering and cracking.
- Tempered glass will withstand temperatures of up to 470 degrees Fahrenheit (243 degrees Celsius)
- A tempered glass roof can hold heavy, wet snow for very long periods without shattering.
- If tempered glass does break, it will shatter into small pieces.
- Laminated glass is solid and is exceptionally resistant to high winds and harsh weather.
- Laminated glass can block out up to 99 percent of incoming UV radiation.
- Clear glass enhances the appearance of a greenhouse.
- Glass is readily available and easy to replace if it breaks.
Cons Of Using Glass Roofing On A Greenhouse
- Glass, and in particular, laminated glass, is the most expensive material to use on a greenhouse roof due to the associated costs of the sturdy frame required to support it. The glass itself is also costly.
- Glass greenhouse roofs must be sealed carefully and properly to prevent leaking.
- Glass is not the best heat insulator.
- Glass can break easier than other materials, except for laminated glass, which is difficult to break.
- Glass needs to be washed regularly to allow light into the greenhouse.
Here’s a video showing what’s involved having a glass greenhouse built, it can get expensive:
Fiberglass Sheets Or Paneling
Fiberglass sheets or panels are best used on permanent greenhouse structures. This material is lighter and does not require the same heavy-duty framing that glass roofing needs.
Pros Of Using Fiberglass Roofing On A Greenhouse
- Fiberglass will last for up to 15 years or more on any permanent structure.
- Fiberglass can withstand all types of weather and outside elements.
- Provides excellent diffused light and great insulation.
- Fiberglass sheets are inexpensive and easy to work with.
- Fiberglass is one of the cheapest greenhouse roofing options.
Cons Of Using Fiberglass Roofing On A Greenhouse
- Fiberglass requires regular maintenance to maintain maximum light permeability.
- Fiberglass is more rigid than other types of roofing materials.
- Fiberglass is hard to clean and can expose dangerous glass fibers if cut.
- Fiberglass does not contract or expand in changing temperatures and climates.
- Personal protection gear like masks, long sleeves, and gloves is required when working with fiberglass sheeting.
Polyethylene Or Plastic Film Roofing
Polyethylene is the perfect roofing solution for temporary, portable, small, or seasonal greenhouses. It is typically used on greenhouses with arched or curved roofs and greenhouse structures with retractable roofs because of its excellent light permeability.
Pros Of Using Polyethylene Roofing On A Greenhouse
- Polyethylene is inexpensive, flexible, and readily available.
- Some types of polyethylene can last up to five years.
- Polyethylene is treated with additives that reflect and radiate heat into the structure.
- Small tears can be treated with a poly repair kit.
Cons Of Using Polyethylene Roofing On A Greenhouse
- Polyethylene is not as durable as glass or fiberglass
- It can get damaged more easily than other roofing material
- Polyethylene roofing will need to be replaced more frequently than other roofing materials
Here’s a video of a greenhouse roof install using Tuftex, with more info about polycarbonate panels below:
Polycarbonate Or Acrylic Roofing
Double-layered polycarbonate acrylic greenhouse roofing is constructed with “webs” between the two layers, retaining the heat. This roofing material should be used on curved roofs and could last for up to ten years.
Pros Of Using Polycarbonate Roofing On A Greenhouse
- Polycarbonate roofing is stronger and more durable than other roofing materials.
- The best roofing material for energy saving and heat retention.
- Blocks UV rays from the sun while allowing the warmth from the sunlight in.
- Polycarbonate is extremely lightweight, making it easy to work with.
- Polycarbonate is extremely easy to maintain and only requires cleaning once or twice a year.
Cons Of Using Polycarbonate Roofing On A Greenhouse
- Polycarbonate does not last as long as glass or fiberglass.
- This type of material is susceptible to yellowing.
- The double-construction layers do not allow as much light to pass through as fiberglass or glass.
- If not installed properly, the double-construction layers can allow moisture to accumulate between the layers creating algae.
- Replacing broken panels could take time as they are not readily available and need to be ordered from the manufacturer.
A greenhouse roof is the most essential part of the structure. If you do not have the correct glazing or covering over the frame, your plants will most likely struggle to survive or die due to a lack of light and heat.
While there are many different decisions to be made when choosing materials for constructing a greenhouse, the roofing materials should be at the top of the list. By creating the perfect conditions for growing your plants, you could produce your own veggies year-round in your greenhouse.