Greenhouse Shading: Paint, Mesh and Blinds Compared

Illustration of staging and potted crops inside a greenhouse

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Greenhouse shading is the practice of reducing the amount of direct sunlight entering a growing environment to prevent plants from overheating and suffering tissue damage. While ventilation is essential for air exchange, it is often insufficient on its own during the peak of summer. Shading helps limit heat buildup. The RHS uses about 25–27°C as a general management guide, but suitable temperatures and heat tolerance depend on the plants and conditions.

Table of Contents

Diagnosing the need for shading

Gardeners should monitor their greenhouse with a maximum-minimum thermometer to identify when shading is required. If temperatures consistently exceed 27°C, plants are at risk. Physical signs that a greenhouse is overheating include:

Sun-flag: A partial collapse of the plant’s structure.
Leaf scorch: Brown or bleached patches on the foliage where the sun has burnt the tissue.
Desiccation: Tender young shoots and seedlings drying out rapidly.

It is important to note that not all plants require shading. Many sun-loving succulents need less shade than leafy crops, but species differ and recently moved plants can scorch. They still need appropriate ventilation and protection from excessive heat.

Shading paints: application and limitations

Shading paints are liquid coatings diluted with water and applied to the exterior glass. They are typically introduced in mid-spring and removed in early autumn. As the summer intensifies, gardeners can apply thicker coats to increase the level of shade.

Practical application: These paints are brushed onto the outside of the glazing. Some formulations are designed to become translucent when wet, allowing more light through while the coating is wet; follow the product’s removal instructions separately. In September, the coating should be washed and brushed off as light levels fall.

Suitability constraints: Shading paints are not recommended for all structures. They are less suitable for:

Unpainted timber: The paint may stain natural wood frames.
Polycarbonate or acrylic: These materials may not release the paint easily, leaving visible traces even after thorough cleaning.

Shade netting and polyethylene mesh

Polyethylene mesh, often referred to as shade netting, is a cost-effective alternative to blinds. It is typically fixed inside the greenhouse using clips, although external fitting provides a superior cooling effect by stopping the sun’s rays before they hit the glass.

The primary advantage of mesh is its price and ease of installation. However, because it is made of plastic, it can deteriorate with weather and ultraviolet exposure and eventually need replacement. Do not assume ordinary polyethylene is biodegradable; collect fragments and dispose of it appropriately. Mesh is a static solution; once clipped in, it cannot be adjusted as quickly as a blind during a period of dull weather.

Comparing internal and external blinds

Blinds offer the most flexibility for managing light levels throughout the day, but their effectiveness varies significantly based on their position relative to the glass.

External blinds

External blinds provide the maximum cooling effect. By blocking the sun’s rays before they pass through the glazing, they intercept sunlight before it enters, reducing the heat load. They can be drawn up quickly during cloudy spells to ensure plants receive maximum light for growth and cropping, which is particularly vital for edible crops like tomatoes.

Internal blinds

Internal blinds are generally easier to automate, allowing them to deploy exactly when the sun is at its peak. However, they are less effective at cooling because sunlight must first pass through the glass, which generates heat inside the greenhouse before the blind can block the light.

Managing humidity and transpiration

Shading is only one part of temperature control; humidity also plays a role in leaf cooling. Plants cool themselves through transpiration—the process of water moving through the plant and evaporating from the leaf pores. If the air is too dry, plants may wilt because they lose water faster than the roots can absorb it.

To support the cooling effect of shading, damping down may help crops that benefit from increased humidity, alongside root watering and ventilation. This involves wetting the hard surfaces of the greenhouse, such as paths and floors, when appropriate for the plants and conditions, without creating persistently wet surfaces. This increases atmospheric humidity and helps prevent heat stress. However, this should be done early in the day; if the greenhouse remains damp during cool September nights, it can increase the risk of grey mould (Botrytis) and the damping off of seedlings.

Summary of shading methods

Method	Position	Cooling Effect	Flexibility	Best For
Shading Paint	External	High	Low (Seasonal)	Glass structures, budget-conscious
Mesh/Netting	Internal/External	Medium to High	Low	Polytunnels, temporary setups
External Blinds	External	Maximum	High	Maximum heat control, variable weather
Internal Blinds	Internal	Low to Medium	High	Automation, ease of installation

Useful products for this job

The links below open Amazon UK product searches. Check the exact item, seller, current price and compatibility before buying.

Greenhouse shading paint: Used for external application to reduce heat and light on glass structures. Ensure the paint is suitable for your glazing material; avoid using on polycarbonate or acrylic unless specified. Search Amazon for Greenhouse shading paint.
Polyethylene shade netting: A budget-friendly option for internal or external shading. Check the percentage of shade provided to ensure it doesn't overly restrict light for edible crops. Search Amazon for Polyethylene shade netting.
Maximum-minimum thermometer: Essential for diagnosing when shading and ventilation are required based on temperature peaks. Ensure it is designed for outdoor/greenhouse use with a clear reading scale. Search Amazon for Maximum-minimum thermometer.

Related garden guides

Sources and further guidance

Guidance researched in September 2026. The feature image is an AI-generated illustration. Product guidance is based on published information, not hands-on testing.