Combine Two Ventilation Types

If you can’t get the same temperature inside your tunnel as outside, you need to add ventilation capacity. When plants don't have enough energy, high temperatures lead to blossom drop. 

The two best options for complementing roll-ups are:

1. Peak Vents

Pros :

• The most effective way to expel hot air, due to the chimney effect
• Large opening along the entire tunnel length = maximum exchange
  
• Easily automated

Cons :

• Expensive (a few thousand dollars)
• Difficult to install, especially in an existing tunnel
  
• Best installed when replacing the plastic covering

2. Positive Pressure Fans

Pros :

• Affordable ($500)
• Quick installation (half a day)
  
• Easily automated

Cons :

• Consume electricity ($100/year)
• Noisy
  
• Less effective than peak vents
  
• Requires plastic tubing for uniform air distribution

Which one is the best?

When you consider building a new tunnel, go for peak vents. They are incredibly effective.

If you already have your tunnel, the best option is a positive pressure fan. I recommend getting two of these fans for a 30' x 100' tunnel.