Collection: Fan

Why Air Movement Matters

A greenhouse traps air as well as heat. Without movement, warm air collects at the ridge while the floor stays cold, moisture settles on leaves and glazing, and still pockets form where fungal spores take hold. A greenhouse fan addresses all three by keeping the air turning over.

The effect on disease is the practical benefit. Botrytis, mildew and damping off all need still, humid conditions to establish. Gentle constant circulation makes the environment considerably less hospitable to them, and it does so without you having to do anything daily.

Circulation or Extraction

The two types do different jobs and are not interchangeable.

• Circulation fans move air within the house. They run continuously at low speed, even the ridge and floor temperatures out, and dry leaf surfaces after watering.
• Extractor fans move air out of the house through a vent panel, pulling cooler air in behind it. They are for shifting heat in summer rather than for daily circulation.

Most houses benefit from circulation year round and extraction only in the warmest months. In a small frame, passive vents and louvres will often handle the summer load on their own.

Solar and Mains Models

Solar fans need no supply and suit allotment plots and any greenhouse without power. They run when the sun is on the panel, which broadly matches when the house is warming, though they stop as soon as cloud passes over.

Mains models run continuously and can be controlled by a thermostat or timer. If you already have a supply for an electric heater, running a fan from the same circuit is straightforward.

Positioning

Height and direction matter more than power. A circulation fan mounted high and angled along the length of the house sets up a slow loop that reaches the whole volume. Aimed directly at plants it does more harm than good, drying foliage and stressing seedlings.

For extraction, the fan goes high at one end with an inlet low at the other. Air needs somewhere to enter or the fan simply works against a closed box.

Fans Alongside Other Climate Control

A fan moves air but does not cool it. In midsummer, shading removes heat before it enters, which is more effective than trying to shift it afterwards. Our shading range covers nets, blinds and shade paint.

A maximum and minimum thermometer will show whether your problem is peak temperature or stagnant humidity, and those need different answers.