What size extractor in your grow room?

When setting up a successful grow room, choosing the right extractor and filter is essential. A good ventilation system not only provides fresh air, but also prevents mould, odour problems and an unhealthy environment for your plants. In this article, we explain how to choose the right size extractor and filter, and how different types of lamps affect your choice.

Why is an extractor important?

An extractor ensures that the air in your grow room is continuously refreshed. This is crucial for bringing CO2 to your plants, removing excess heat and maintaining stable humidity. Without good ventilation, your plants can stagnate in their growth and you run the risk of pests and diseases.

How do you determine the right size extractor?

To calculate the correct capacity of your extractor, it is important to know the volume of your grow room. You calculate this as follows:

1. Calculate the volume of the room: Multiply the length, width and height of the room. For example: a room 2 metres long, 2 metres wide and 2 metres high has a volume of 8 cubic metres (2 x 2 x 2 = 8 m³).

2. Consider the air exchange rate: Ideally, the air in your grow room should be changed 20 to 30 times per hour. This means multiplying the volume of the room by 20 to 30. In our example, you need an extractor with a capacity of at least 160 m³ per hour (8 x 20 = 160).

3. Factors requiring additional capacity:

   • High temperatures: When you use powerful lights like HPS lamps, you generate more heat, which requires a stronger extractor.

   • Use of carbon filters: A carbon filter reduces the efficiency of your extractor by about 25%. So make sure your extractor has more capacity to compensate.

Which filter fits your extractor?

A carbon filter is essential to neutralise odours created during cultivation. The size of the filter should match the capacity of your extractor. Here are the main points of interest:

1. Capacity of the filter: Make sure the filter can handle the same or higher air capacity as your extractor. For example, an extractor with a capacity of 160 m³/h requires a carbon filter that can handle at least 160 m³/h.

2. Diameter of connection: The diameter of the filter should match the connections of your extractor and ventilation hoses. Common sizes are 100 mm, 125 mm and 150 mm.

3. Lifespan: A carbon filter has a limited lifespan, usually 12 to 18 months, depending on use. Replace it on time to avoid odour problems.

How do lamps influence your choice?

The heat and light spectrum of your lamps have a big impact on the climate in your grow room. Here are the most commonly used types of lamps and their impact:

1. HPS lamps (High Pressure Sodium):

• Advantages: High light output, ideal for the flowering phase.

• Disadvantages: Produces a lot of heat.

• Impact on ventilation: When using HPS lamps, a powerful extractor is necessary to dissipate heat effectively. Combine this with a fan to distribute the heat evenly.

2. LED lamps:

• Advantages: Energy-efficient, less heat production, long lifespan.

• Disadvantages: Higher acquisition costs.

• Impact on ventilation: Because LED lamps produce less heat, you can choose an extractor with a lower capacity. This saves energy and makes the system quieter.

3. CMH (Ceramic Metal Halide) lamps:

• Advantages: Complete light spectrum, suitable for growth and flowering phases.

• Disadvantages: Produces more heat than LED, but less than HPS.

• Impact on ventilation: Choose an extractor that can dissipate enough heat, but does not need to be as powerful as with HPS.

Sample calculation

Suppose you have a grow tent measuring 1.5 x 1.5 x 2 metres (4.5 m³) and uses a 600-watt HPS lamp:

1. Volume: 4,5 m³.

2. Required capacity without filter: 4.5 x 20 = 90 m³/h.

3. Compensation for filter: 90 x 1.25 = 112.5 m³/h.

4. Recommended extractor: Choose a model with a capacity of at least 120 m³/h.

5. Filter: Use a carbon filter with a capacity of at least 120 m³/h and a connection diameter that matches your extractor.

Additional tips

• Sound: Consider a silencer if your extractor makes a lot of noise.

• Air conditioning: Use a climate controller to make the extractor automatically respond to temperature and humidity.

• Additional fans: Install oscillation fans to improve air circulation in the room.

Choosing the right extractor and filter for your grow room is a crucial step in ensuring an optimal climate for your plants. Calculate the volume of your space, take into account the capacity of your extractor and make sure your filter matches your ventilation system. Don't forget to also take into account the heat production of your lamps, as this can significantly influence the requirements for your ventilation system. By carefully tuning these factors, you will lay the foundation for a successful grow.