How To Ventilate A Greenhouse (2 Best Options)

An efficient ventilation system is crucial in keeping your greenhouse at the right temperature while preventing excessive moisture buildup in your growing space. If you’re planning on using your greenhouse to grow plants throughout the year, you must have a way to regulate temperature and humidity levels within the structure properly. It will ensure that your plants don’t get stressed out or sick from too much heat, cold, or humidity. 

The best way to ventilate a greenhouse is by Installing vents and fans at strategic positions inside it. Circulating fans near the ceiling and roof vents are the most efficient ventilation method compared to the standing fans and side vents in the greenhouse walls.

This blog post will explain how you can install and operate ventilation systems in your greenhouse to maximize plant growth without having to worry about them getting too hot or dry.

What is the need for ventilation in a greenhouse?

Installing a proper ventilation system is crucial for carbon dioxide replacement and air circulation within a greenhouse. Plants use carbon dioxide for photosynthesis, so its level keeps dropping inside the greenhouse. Fresh air brings more carbon dioxide with it and replenishes the decreased levels. Without proper ventilation, plants can’t thrive and eventually die down.

Moreover, poor air circulation can increase humidity levels that can negatively affect plant activity and lead to plant diseases and pests. On the other hand, a consistent air exchange will help plants flourish by maintaining an optimal temperature range. Without adequate air circulation, a greenhouse will get too hot on one side and too cold on another.

A greenhouse
A greenhouse

Greenhouse Ventilation Options

Growers use several methods and tactics to ventilate their greenhouses according to their specific needs. There are two main methods of greenhouse ventilation:

1. Natural ventilation

Passive ventilation methods include cross venting through sidewall vents and roof vents. In passive ventilation systems, pressure differences allow outside air to flow into the greenhouse while naturally letting the inside hot air out. This method works better on cool days as a larger difference in temperature builds a better air exchange. 

However, natural ventilation system doesn’t work in high humidity when you need evaporative cooling. When opting for natural ventilation in your greenhouse, you need to consider the following things for effective ventilation through the sidewall and roof vents.

Vent size 

For some greenhouses, such as hoop houses, rolling up the sides may be enough during warm days. However, in rigidly structured greenhouses, you need to follow some important guidelines for an effective ventilation system. It is recommended that the combined roof vent area be the same as the combined sidewall vents area. In addition, having large vents gives better ventilation.

Vent location

Typically, greenhouse roof vents are hinged on both sides of the ridge, which helps in creating a vacuum to draw the hot air out. Gutter vents are not an effective way of ventilation in a greenhouse. The usual location of sidewall vents is on bench height. However, installing these vents a little higher keeps the plants safe from direct cool air during winter.

Greenhouse orientation

If possible, construct a greenhouse in a direction so that the sidewall gets the summer wind without any difficulty. Also, ensure that trees, buildings, or other obstructions don’t affect the natural airflow. The local weather department can help you determine the wind direction.

2. Fan ventilation

A greenhouse needs a certain level of wind speed for effective ventilation. The wind speed is often not enough to enable cross ventilation in the greenhouse naturally. It is where you’ll need a proper active ventilation system. 

Active cooling systems are more efficient than passive methods. They use electrically powered circulating fans, exhaust fans, and intake fans that push or pull air into or out of a structure. Although fans prove to be a better way of ventilating greenhouses, a combination of both natural and active ventilation methods is the best and most cost-effective option in most scenarios.

Besides, fan ventilation is the best method for hot climates as it quickly draws in fresh air while significantly cooling the environment. However, the fan’s type, placement, and operating cost also play a major role in the efficiency of the whole ventilation system. 

Fan type 

When natural ventilation is not working, you need automated atmospheric controllers or thermostatically controlled fans. These are the perfect options for your temperature and humidity control needs, which are impossible to regulate with ordinary exhaust fans.

For longer greenhouses, oscillating fans or boosters prove a great tool in creating fresh air movement. They are helpful in evenly distributing fresh air throughout the length of the greenhouse to ensure ideal conditions for each plant.

Fan placement

Hot air rises, so the exhaust fans should be placed or installed at high points. On the other hand, place the intake fan on the ground opposite the exhaust fan. It will ensure cross-ventilation across the length of the greenhouse and help the ventilation system to perform more efficiently.

Cost of running fans

One this that should be considered when opting for active ventilation is the cost of running the fans. It’s an ongoing operational cost while you may also bear additional costs for keeping the fans in running condition and their maintenance.

Natural or fan ventilation – Which one is better?

Many people assume that fan ventilation is better than natural ventilation. However, that’s not always true. Both have their advantages and shortcomings. You should choose one according to the size of the greenhouse and your budget. However, don’t ignore the needs of your specific project and the outcomes you will have with proper ventilation.

Final thoughts

The simplest ventilation system used in a greenhouse comprises sidewall vents, roof vents, and maybe an exhaust fan if necessary. Some gardening experts believe that opening the windows of the greenhouse will allow natural ventilation to take place. While this may be true in certain situations, greenhouses are artificially created environments so they may need proper ventilation methods for a healthy plant environment.

In short, strategically installed fans alongside natural ventilation are the perfect option to fulfill most of your greenhouse’s ventilation needs while keeping your operating costs under control.

Charles John

A novice DIYer who learns about home ventilation. I am a mechanical engineer and have a basic knowledge of HVAC systems but I learn continuously to make myself the best blogger in that space.

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