How to Keep Your Greenhouse From Overheating?

Does your DIY greenhouse kit feel like a sauna in the summer months? Are you struggling to keep your delicate plants from wilting, sweating, and drooping despite your best efforts? You are not alone.

Polycarbonate greenhouses are designed to soak up the sun and keep your growing space warm and cozy throughout the seasons. While this works wonders for extending your planting season into the winter, managing the heat on those sweltering summer days can be challenging.

The good news is there are countless ways to lower your temperatures, upgrade your DIY backyard greenhouse and ensure your plants are thriving during the sunniest months!

To kick off this growing season, we’ve compiled our top tips and tricks to keep your greenhouse from overheating.

In this guide you will learn:



What Temperature Should Your Greenhouse Be?

First and foremost, it’s essential to understand what the perfect temperature for your DIY backyard greenhouse should be. Ideally, anywhere between , 80-85°F (26-29°C) is the golden standard throughout the spring and summer months. 

Anything higher than 90°F (32°C) is cause for alarm.

We suggest monitoring your greenhouse temperatures with a good thermometer. However, if you don’t have one – walk inside your greenhouse and see how it feels.

If it’s too hot for you, it’s most likely too hot for your plants as well.

5 Ways to Keep Your Greenhouse Cool

While these tips can alleviate some of the heat on their own, many DIY greenhouse for beginner gardeners find they’re much more effective when implemented together.

1. Regular Watering

We know this tip may seem obvious, but it is the most important. Consistent watering is crucial for your plants to flourish and keep your greenhouse temperatures down..

How does this work? Whenever you water your plants, they’ll release moisture through their leaves and, in turn, lower the inside temperature. This process of transpiration helps keep your garden from wilting and is the easiest way to keep your greenhouse cool on sweltering summer days.

We all forget to water our plants now and then, so having reminders set up on your phone or an automatic watering system will ensure your garden gets the hydration it needs. 


2. Install Ventilation Windows

Managing the heat in your DIY greenhouse kit is also heavily reliant on adequate airflow.

Ventilation windows are a great way to bring in a fresh breeze from outside and allow the hot air to escape, giving your plants a break from a hot and stuffy enclosed space.

The number of windows you should install depends on the size of the greenhouse kit, the climate you’re located in, and the plants you’re hoping to grow.

The main takeaway is to have enough areas for the heat to get out. However, as an example, the following numbers tend to work well for our Sungrow models:

Are you looking for a low-effort ventilation solution?

Try installing heat-activated automatic windows. They’ll open up when the inside temperature rises to a certain point and close once the day cools down. Not to mention, they’re especially handy if you don’t have time to monitor your greenhouse temperature all day.

3. Dampen Down The Inside

Dampening down is another great low-cost trick to keep your greenhouse cool. It’s as simple as grabbing your hose or bucket of water and wetting the floor of your greenhouse.

This easy process helps to increase the humidity inside your greenhouse. As the water evaporates, the inside moisture levels rise, allowing your plants to cope on sweltering hot days.

Feel free to dampen down your greenhouse as often as you need. Just be mindful that if you choose to do this regularly, you will need appropriate ventilation to avoid an excess buildup of moisture.

4. Promote Airflow With Fans

When it comes to air circulation, a good-quality fan or cooler is your best friend. However, while a fan on its own may struggle to dramatically lower your inside temperature, it will work most effectively alongside ventilation windows and watering.

There are countless benefits to having added airflow in your greenhouse. A fan will help:

  • Regulate temperatures by pushing hot air out through windows and any greenhouse door openings.
  • Prevent pests, mildew, and diseases from accumulating due to high humidity & lack of airflow.
  • Improve pollination levels by mimicking the outdoor breeze that many plants rely on to grow.

When installing your fan, it all comes down to what placement you find the most effective. Experiment with your fan near the floor, in front of windows, or in the top corner of your greenhouse to discover what works best for your setup.


5. Add a Shade Cloth

A little bit of shade can go a long way to protect your garden from extreme heat. Shade cloths are a handy tool for lowering greenhouse temperatures and filtering out excess UV rays.

Heavy-duty shade netting tends to be made from durable polyethylene. While you can find them with varying shade levels, we recommend opting for a 50% density so your plants can still get enough sunshine to flourish.

You can easily install your shade cloth over the roof of your greenhouse. However, if you need a less permanent solution, try hanging your shade cloth directly over your garden beds or attaching it from a wire inside the greenhouse. That way, it can be unclipped and rolled away on cloudier days

Make Sure Your Plants Flourish This Summer

For gardeners living in cooler climates, high greenhouse heat levels may seem like a solution to many growing challenges. But the reality is, there can be too much of a good thing.

Your greenhouse is an incredible tool to promote healthy plant growth and extend your growing season well beyond summer. However, it takes regular monitoring and a human touch for your garden to thrive in any environment.

Whether you’re preparing for a new season or troubleshooting the challenges of an overheating greenhouse, these 5 tips will help you ensure your plants flourish this summer.

So what are you waiting for? Planta offers Backyard Greenhouse Kits in British Columbia and all the way to Ontario. Regardless of your climate, we'll find the perfect solution for you. 

Have any questions? Don’t hesitate to leave a comment below, and one of our greenhouse experts will get back to you shortly.


Why Planta Greenhouses?

Back to Learn

Share Your Thoughts

Ask thoughtful questions, share helpful tips, or offer words of encouragement for other greenhouse owners.