Greenhouse Cooling: How to Keep Your Plants Safe in Hot Weather
When the sun beats down and your greenhouse, a structure designed to trap heat for growing plants year-round turns into an oven, your tomatoes won’t thrive—they’ll wilt. Greenhouse cooling isn’t optional in the UK, especially during unexpected heatwaves. It’s not just about opening a window. It’s about managing airflow, blocking excess sun, and keeping humidity in check so your plants stay healthy, not stressed. Without proper cooling, even hardy plants like peppers and cucumbers can stop growing, drop fruit, or get fried by midday sun.
One of the most common mistakes is assuming a greenhouse stays cool just because it’s made of glass. In reality, glass traps heat like a car in summer. That’s why ventilation, the process of moving air in and out to regulate temperature and humidity matters more than you think. Roof vents, side vents, and even automatic openers that respond to heat can make a huge difference. Then there’s shade cloth, a lightweight fabric that blocks direct sunlight while letting light and air pass through. A 50% shade cloth isn’t just for tropical plants—it’s a must-have for any UK greenhouse in July. And don’t forget water. Misting systems or even just dampening the floor can cool the air naturally, without electricity.
Many gardeners overlook how plant placement affects temperature. Crowded plants block airflow and raise humidity, which makes things worse. Spacing them out, using raised beds, and keeping paths clear helps air move. Even simple things like painting the inside glass with whitewash in spring can reflect sunlight and cut heat by up to 30%. And if you’re using a polytunnel instead of a glasshouse, the same rules apply—just make sure your vents are high and your sides can roll up.
What you’ll find below are real, tested tips from UK gardeners who’ve been there. Whether it’s how to pick the right shade cloth for your size greenhouse, why fans sometimes do more harm than good, or how to use recycled materials to cool your space for under £20, these posts cut through the noise. No fluff. No theory. Just what works when the thermometer climbs and your plants are begging for relief.