greenhouse ventilation open window

Proper greenhouse ventilation is essential for your plants’ wellbeing

Gardening enthusiast and exotic plant lover Clive Harris of DIY Garden shares his knowledge on why greenhouse ventilation is so important.

Many novice gardeners are afraid of greenhouses, considering them high-maintenance mediums for demanding plants. However, modern advances have made greenhouse cultivation a cinch compared to previously, meaning you can now harvest your home-grown spoils with minimal cost, time and effort.

Temperatures inside a hothouse can rise more than 15% higher than outside, creating the ideal environment for producing exotic species that generally grow in hotter climates. This extra heat also provides the perfect conditions for nurturing your seedlings during winter, giving them a head start for the coming season.

Why Is Greenhouse Ventilation So Important?

Ventilate your greenhouse so that plants don’t bake in the summer heat!

Imagine being locked inside a hot car with the windows up on a sweltering summer day. Without ventilation, this is what your plants and vegetables are exposed to. Even the most tropical species will suffer in extreme heat, risking dehydration, leaf scorch and sun-flag. Any temperature over 27°C has the potential to damage your crops.

Ventilation has several benefits. As well as offering greater control over the internal temperature and humidity, it also increases airflow which is crucial for effective photosynthesis and pollination.

There are two types of ventilation systems – passive and powered. Passive or natural systems are the most common type found in small greenhouses. They use a series of ridge and sidewall vents which help to draw cool air in and dissipate the heat. In high summer, the greenhouse door can be opened to give extra ventilation and airflow.

Traditional powered mechanical ventilation systems involve the use of exhaust and circulation fans to maintain an ideal atmosphere inside the greenhouse.

However, I’m a huge fan of automatic ventilation systems as they use solar energy to automatically open the vents. No electrically required, and 100% environmentally friendly!

 Maintaining Optimal Greenhouse Conditions

Proper shading will help lower the temperature in the summer

Greenhouses are prone to overheating between spring and autumn, so keeping a close eye on the environment is vital for the survival of your harvest. Constant plant patrol sounds tedious, especially during summer months, so it’s just as well that technology has made it infinitely easier for the modern horticulturist.

Back in the good old days, a gardener would need to traipse back and forth many times a day in hot weather to check and adjust the temperature in their greenhouse. Thankfully, the advent of portable weather stations means the temperature can now be monitored remotely via smartphone.

Opening and closing the vents is another chore that has become effortless. Solar powered and heat sensitive vent openers are now available which automatically release once the temperature reaches a certain point.

Adequate shading will help to keep your plants cool in the scorching summer heat. Fit blinds to the exterior or interior of your hothouse to avoid overheating. A cheaper option to blinds is shade netting which works on a similar principle. For a quick and easy solution, shading paint can be applied to the exterior of the panes to prevent heat penetrating the glass. This can then be washed off once the weather becomes cooler.

During the hottest months, it is crucial to sustain humidity within the greenhouse. This can be done by damping down the interior regularly.

Contemporary greenhouse gardening has become straightforward and stress-free, meaning there’s no longer any reason to avoid those shiny glass panes. You’ll be on your way to prizewinning hothouse flowers in no time!


Find out more about growing under glass at our dedicated greenhouses hub page.

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