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!