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About Greenhouse Ventilation
Greenhouse ventilation moves hot, stale air out and cool, fresh air in. Good airflow improves fruit set, lowers disease pressure, and stops leaf scorch on hot days. Our range covers roof vents, louvre vents, and automatic openers. Parts start from £29 for a replacement opener piston.
We fit these vents on customer greenhouses every week. The pattern is simple. Cool air enters low through louvre vents. Hot air rises and leaves through roof vents near the ridge. This is the chimney effect, and it works without power. Aim for vent area equal to about 20% of your floor space. An 8x6ft house needs roughly two roof vents plus two louvres. Most parts dispatch within 5 days with free UK delivery.
"Most overheating calls we get trace back to one undersized roof vent. We tell customers to add a louvre low on the opposite side. The temperature drop is immediate."
— Matt W, Greenhouse Stores installer💡 Tip: Open vents in the morning, before the sun hits the glass. Waiting until noon traps an hour of damaging heat around your plants.
🔧 Matt's Installation Tip: Fit the opener before the season
Wax cylinder openers stiffen with age. Fit a fresh one in early spring. Test it in warm water first. The arm should extend smoothly as the wax warms. Replace the cylinder, not the whole unit, when it slows.
Matt's Pick for Hands-Off Ventilation
Best For: gardeners who are out all day
Why I Recommend It: the Bayliss MK7 lifts heavy glazed vents and rarely fails. I fit them most.
Price: from £89
Comparing your ventilation options
| Option | What it does | Best for | From |
|---|---|---|---|
| ⭐ Matt's Pick: Bayliss MK7 Auto Opener | Opens heavy roof vents on heat alone | Busy gardeners, larger vents | £89 |
| Roof vent | Lets hot air escape at the ridge | Every greenhouse, fitted high | £79 |
| Louvre vent | Draws cool air in low down | Cross-flow, hot south-facing plots | £83 |
| Replacement piston | Revives a slow auto opener | Older openers, budget fixes | £29 |
Frequently Asked Questions
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How much ventilation does a greenhouse need?
Aim for vent area near 20% of your floor space. An 8x6ft house (48 sq ft) needs roughly two roof vents plus two louvre vents. Split them high and low so air flows through naturally.
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What is the difference between roof vents and louvre vents?
Roof vents sit high and release hot air. Louvre vents sit low and pull cool air in. Used together they create the chimney effect, the most efficient natural airflow for a greenhouse.
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Do automatic vent openers need electricity?
No. Auto openers use a wax cylinder that expands in heat. As temperatures rise the wax pushes the vent open. As it cools the vent closes. No wiring or power is needed.
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When should I open greenhouse vents?
Open vents in the morning before the sun warms the glass. On hot summer days leave them open all day. Close them in the evening to hold gentle warmth overnight.
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How do I stop condensation in my greenhouse?
Improve airflow. Crack a vent overnight so damp air escapes through the roof. Position a louvre low to draw drier air in. Avoid watering late in the day, which adds moisture.
Need help sizing your vents?
Browse the full ventilation range above, or call our team on 0800 098 8877 for advice matched to your greenhouse model.