Everything You Need to Know About Ventilation

Tunnel at Dusk

If you are new to polytunnel ownership or looking to buy a bigger tunnel than you are used to, then ventilating is something you need to consider. Ventilating your tunnel is important for a couple of reasons; maintaining a climate will help crops thrive and promoting good air circulation will reduce diseases. 

While keeping tender plants warm is important, that doesn’t give you free rein to bake them in the summer! It is also worth considering the difference in temperature between the height of the day and the night, too much of a range in temperature can cause some plants to react poorly. Ventilation can help keep tunnels a little cooler in the day but be closed at night to maintain a more constant climate. 

Disease is also an important factor. Hot and humid conditions with stagnant air will help diseases to take hold of your crops and allow them to spread like wildfire through your tunnel. Good air circulation will help prevent diseases initially and keep them in control if they do take hold. So what ventilation should you consider for your tunnel?



Tunnel Doors

An obvious solution, however, it is common practice to see polytunnels with their doors propped open during the summer to promote ventilation and pollination. This does leave your tunnel vulnerable to pests looking to nibble on your flourishing crops, though this can easily be resolved with some strong netting. Depending on the length of your tunnel, your door may be enough to maintain the temperature, however, for many tunnels, it is not enough through the height of summer. Our doors are available with PVC ventilation panels, allowing the perfect middle when you are looking to maintain circulation without keeping the door open.

Side Vents

Tunnel Side Vents

Over a certain length, some tunnels struggle with stagnant air in the middle where open doors cannot circulate. The best recourse for this is to opt for some side ventilation. This allows air to flow directly into the hot pockets of your tunnel and can be closed during cooler months, allowing better control over the temperature of your tunnel. Depending on the width and placement of the tunnel, you can install side vents on one side or both. A more exposed tunnel may only need side vents down one length, but a sheltered tunnel will not see the same results and may require both sides to be open to ventilation. Side vents work in conjunction with open doors, allowing full circulation through the tunnel.

Roof Vent

Roof Vent

For people looking to release heat as opposed to promoting circulation, a roof vent may be the perfect solution. Cord operated with a spring closing mechanism, this is a great way to control the temperature in your tunnel. If you have concerns over adding side vents (maybe too exposed?) then opening doors can introduce fresh air, while the roof vent releases the heat and humidity. 

Another key thing to remember with polytunnels is that height and length factor into how much ventilation you will need, as well as the placement of your polytunnel. Though longer tunnels are prone to hot spots of stagnant air, tunnels with more height will have better air circulation. As tempting as it is to buy a long low tunnel to optimise growing space, ensure it is ventilated properly. This will help you have the healthiest crops that are not plagued by disease or baked.


Image Credit: Plews Garden Design