Grow Room Ventilation & Environment Control: How to Maximise Yields

The key to a thriving indoor grow is environment control. Perfect your grow room ventilation, and your plants will reward you with better growth and yield.

Your objective is clear:

• Bring in fresh, CO₂-rich air.
• Remove stale, CO₂-depleted air.

To achieve this, you need to master:

• Air intake and extraction
• Air circulation
• Temperature control
• Humidity regulation

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1. Grow Room Ventilation: Air Intake & Extraction

Why Ventilation Is Essential

Proper airflow ensures plants photosynthesise efficiently, reduces mould risk, and maintains a healthy grow environment.

Ventilation Methods

1. Passive intake with extractor fan
2. Intake and extractor fans with oscillating recirculation
3. Diffuse Air Systems for full coverage airflow

Pro Tip: Choose a fan that exceeds your immediate needs—you’ll be covered if your setup scales up.

Calculating Fan Size

Step 1 – Measure your grow area:
Length × Width × Height

Example: 2.4m × 2.4m × 2m = 11.52 m³

Step 2 – Convert to airflow per hour:
Multiply by 60: 11.52 × 60 = 691.2 m³/h

Step 3 – Account for lighting heat:
For every 2W, extract 1 m³/h.
Example: 4 × 600W = 4 × 600 × 0.5 = 1200 m³/h

Step 4 – Add extra lighting:
An additional 1000W lamp = +500 m³/h → total 1700 m³/h extraction needed.

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Factor in Filters & Ducting

Filters and bends reduce airflow. For instance, the RVK 150 L1 drops from 720 m³/h to 580 m³/h when paired with a Carbo Air filter thehorticulturecompany.co.uk+7thehorticulturecompany.co.uk+7thehorticulturecompany.co.uk+7Homebuilding+1.

To handle this, consider high-performance options like the [Dutch Touch PRO Carbon Filter](https://thehorticulturecompany.co.uk/product/dutch-touch-pro-carbon-filter/) thehorticulturecompany.co.uk which uses ultra-absorbent carbon and offers extended service life.

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Achieve Negative Pressure

Ensure your intake fan runs at up to 25% lower airflow than your extractor to maintain negative pressure and control odours Architectural Digest+11thehorticulturecompany.co.uk+11thehorticulturecompany.co.uk+11.
For passive intake setups, ensure your vents are large enough. In winter, diffuse cold air or draw warmer indoor air to prevent plant shock.

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2. Circulation Fans & Air Diffusion

Even with extraction, stagnant air can form hot spots and microclimates.

Use tools like the [GORILLA 12″ Rotating Box Fan](https://thehorticulturecompany.co.uk/product/blt12rotatingboxfan/) for reliable air movement. It offers multiple speeds, timer, and durable build—perfect for humid grow spaces thehorticulturecompany.co.ukthehorticulturecompany.co.uk+3thehorticulturecompany.co.uk+3thehorticulturecompany.co.uk+3.

You can also:

• Use oscillating fans made for grow rooms.
• Install inline fans to move cool air upward.
• Invest in Diffuse Air Systems to eliminate hot and humid zones entirely.

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3. Fan Speed Controllers

A grow room climate controller keeps temperature and humidity in check. Opt for UK-rated equipment—to avoid reliability issues from cheaper imports—and deliver better results long-term.

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4. Reducing Fan Noise

Keep your grow stealthy:

• Fit duct silencers directly after fans.
• In noisy setups, use two in series to significantly reduce sound.

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5. Ideal Grow Room Temperature

• Day (lights on): ~24 °C
• Night: Just 2–3 °C lower to protect yields
• With CO₂ enrichment, you can raise daytime temps slightly.

In winter, use a thermostat-linked heater (e.g., oil-filled or tube type) for consistent warmth.

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6. Humidity Control

Different growth stages require specific humidity:

Stage	Day Humidity	Night Humidity
Seedlings & clones	~70%	~55%
Veg / Early bloom	60–65%	50–55%
Late flower	53–55%	~50%

Automate with a humidifier and dehumidifier on a controller to reduce stress and maximise yields.

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7. Ducting & Fittings

Keep duct runs:

• Short
• Straight
• Free of sharp bends to reduce pressure loss
• Size-matched to the fan for optimal flow

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8. Carbon Filters for Odour Control

Filters like the Dutch Touch PRO are vital for removing odours. Always match filter capacity with fan airflow to maintain effectiveness thehorticulturecompany.co.uk+1Architectural Digest+6thehorticulturecompany.co.uk+6thehorticulturecompany.co.uk+6thehorticulturecompany.co.uk+1thehorticulturecompany.co.uk+1.

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Final Grow Room Setup Tips

• Invest in high-quality fans—they run longer and perform better.
• Protect your intake with mesh filters to block pests.
• Position intake and extract at opposite corners for full-room airflow.
• Maintain balance in every environmental factor—and your plants will thrive.

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Internal Links to Key Product Pages

[Ventilation Systems] and related categories in one place thehorticulturecompany.co.uk+1itor and maintain the right temperature.

[Extraction Fans & Kits] – browse your options here thehorticulturecompany.co.uk+3thehorticulturecompany.co.uk+3thehorticulturecompany.co.uk+3

[Dutch Touch PRO Carbon Filter] – high-performance carbon filtration thehorticulturecompany.co.uk+1

[GORILLA 12″ Rotating Box Fan] – reliable circulation thehorticulturecompany.co.uk