High Tunnel Construction Tips Jack Manix, Walker Farm
Definition: High tunnels are unheated, plastic-covered structures that provide an intermediate level of environmental protection and control compared to open field conditions and heated greenhouses. During all seasons, high tunnels provide protection from wind and rain, which can result in increased crop yields and improved quality as well as decreased incidence of pest and disease problems.
Our First Greenhouse
Square It Up
Squaring Up A Structure
√ Length squared + Width squared = Diagonal
Harnois (Canada)
Poly-Tek (Minnesota)
Rimol (New Hampshire)
Ledgewood Farm (New Hampshire)
IR & Anti-Condensate Plastic
Thermal Film (IR)
Infrared heat blocking additives reduce radiant energy loss. Can block IR heat loss by half , which is 15-25% of total heat loss at night.
Anti-Condensate Plastic (AC)
Anti-fog surfactants make poly covering less repellant to water. Condensate will sheet and run down to the sides of the structure rather than bead and drop on the foliage of plants below. Condensation also reduces light transmission.
Shade Cloth
Advancingalternatives.com
Wiggle Wire 2” x 6” hip board
Endwalls
Roll-Up Secured with Wiggle Wire
Removable End Wall
Baseboard 2” x 12” & 1” x 2’ Blueboard
Tek-Foil Reflects Heat, Cuts Drafts
The Villain
Endwalls Still Standing
Middle Collapse Pulls in Endwalls
Snow Load
• Snow with 1” rain equivalent will load structure with 5.2 psf
• 1” rain may equal 12” fluffy snow or 2-4” heavy wet snow
• High tunnel built from ribs of 20’ pipe bent to create 14’ wide x 6’ high structure will withstand only about 10 psf
• High winds can add to load pressure
Be Vigilant
• Strong endwalls radiate strength towards middle of greenhouse
• 2 inflated layers help snow slide off
• Clear from middles first
• Keep sides clear to make room for snow to slide from structure
Snow Roof Rake 16’ $50-$70
Inexpensive Alarms - $50
Portable LP Heater
Happy Greenhouse Tunnel Growing!