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Greenhoue Ventilation: Negative Air Pressure and Passive Systems

With negative air systems, warm air is sucked out with exhaust fans - air intake is through shutters. Sizing of equipment will depend upon the greenhouse dimensions, the season of the year, the crop and the transpiration rate of the crop.

Passive systems use roof vents and wall openings; air flow through a vent can either be up (warm air rising) or down (cold air dropping). Conditions at any given moment will determine the direction.

Outside wind and interior air circulation (typically horizontal air flow, HAF) will influence the performance of both negative air and passive systems.

The two systems can be used in the same greenhouse - but not at the same time. Negative systems require restricted air intake openings to achieve air flow speed. Because of this, open vents or sidewalls make exhaust fans almost completely ineffective.

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greenhouse light dep
Timer Control for Light Dep
Price: $990.00 plus tax(es)
SALE: $750.00 plus tax(es)

24 hour timer unit for roll up shade systems (Call for a quote) used to adjust the photo-period.
Allows for several openings and closings in a 24 hour period - the benefit is that the curtain can be automatically raised after the sun sets. CSA pre-approval (VEC-CSA) is available as an option.
control for roll up motor
Incremental Controller for Roll Up Motors (thermostat input)
Price: $980.00 plus tax(es)

Automate your roll up walls for a more consistent environment and crop.
Operates 2 roll up motors - they plug into any standard 110v. outlet. The motors are individually fused.
The incremental controllers energize every 10 minutes (adjustable), if the temperature is above the set point, the wall rises 6" (adjustable).
If the temperature is below the set point, the wall drops 6".
Limit switches on the motors determine the lower and upper travel of the motors.
Model VEC-TI is controlled with a thermostat (not supplied - see product code VETH)
CSA pre-approval (VEC-CSA) is available as an option.
shutter style exhaust fan
20" Shutter-Style Exhaust Fan
Price: $508.00 plus tax(es)

Schaefer SFT-2000A 20" Shutter-Style Exhaust Fan, great for greenhouses . Low-maintenance, energy-efficient solution for low to medium airflow. Features an aluminum blade, powder-coated guards, durable aluminum shutters and an enclosed heavy-duty motor. Hardwired electrical connection required. Mounts flush to exterior wall.

Features and Specs:

  • Speed: RPM 14
  • Air Delivery: CFM 3,122
  • Volts: 115/230
  • H/P: 1/3
  • Amps: 3.8/1.9
  • Dimensions: L x W x H 12 ⅜" x 22 ¾" x 22 ¾"
  • Made in United States
shutter style exhaust fan
16" Shutter-Style Exhaust Fan
Price: $385.00 plus tax(es)

Schaefer SFT-1600 16" Shutter-Style Exhaust Fan, great for greenhouses . Low-maintenance, energy-efficient solution for low to medium airflow. Features an aluminum blade, powder-coated guards, durable PVC shutters and an enclosed heavy-duty motor. Hardwired electrical connection required. Mounts flush to exterior wall.

Features and Specs:

  • Speed: RPM 900
  • Air Delivery: CFM 1250
  • Volts: 120
  • H/P: 1/10
  • Amps: 1.3/0.65
  • Dimensions: L x W x H 14" x 22" x 22"
  • Made in United States
shutter style exhaust fan
12" Shutter-Style Exhaust Fan
Price: $310.00 plus tax(es)

Schaefer SFT-1200 12" Shutter-Style Exhaust Fan, great for greenhouses . Low-maintenance, energy-efficient solution for low to medium airflow. Features an aluminum blade, powder-coated guards, durable PVC shutters and an enclosed heavy-duty motor. Hardwired electrical connection required. Mounts flush to exterior wall.

Features and Specs:

  • Speed: RPM 1,550
  • Air Delivery: CFM 760
  • Volts: 115
  • H/P: 1/30
  • Amps: 9
  • Dimensions: L x W x H 8 ⅜" x 14 " x 14 "
  • Made in United States
greenhouse light dep
Roll Up Motor, 156 nM
Price: $290.00 plus tax(es)

Use with a roll up wall up to 150.
Excellent reliability. Ideal for light deprivation and blackout systems.
24 volt DC motor, comes with built in limit switches. Torque: 156 Nm*; RPM: 2.2; Amps: 4 max (7 amps max. load) Revolutions : 40 max; Weight: 4.6 kg. Comes with a coupler 1 3/8" roll up tube. Controllers not included.

*A netwon metre is a unit of torque in the metric system. 156 nM = 115.06 ft-lb.
greenhouse vent, greenhouse shutter
Aluminium Shutter, 30"
Price: $275.00 plus tax(es)

Brushed aluminium.  Automate with shutter motors (requires a thermostat or other controller - not included ) or VEL thermal opener.
rough opening: 30 1/2" wide X 31"
greenhouse haf fan  HAF
12" Air Circulation Fan
Price: $275.00 plus tax(es)

Good air circulation creates temperature uniformity, reduces temperature stratification and promotes evaporation from the leaves (to lessen disease).
We offer Schaefer fans - engineered for high performance and longevity.  Air is thrown in a tight conical pattern, ideal for horizontal air flow (HAF) applications.  Two year limited warranty.
.1 HP, 115/230 volts (1.3/.65 amps) 1554 cubic feet of air per minute
greenhouse haf fan  HAF
8" Air Circulation Fan
Price: $225.00 plus tax(es)

Good air circulation creates temperature uniformity, reduces temperature stratification and promotes evaporation from the leaves (to lessen disease). We offer Schaefer fans - engineered for high performance and longevity. Air is thrown in a tight conical pattern, ideal for horizontal air flow (HAF) applications. Two year limited warranty. .1/100 HP, 115 volts (0.6 amps) 450 CFM air delivery
greenhouse light dep
Roll Up Motor, 44 nM
Price: $198.00 plus tax(es)

Use with a roll up wall 100' or less.
Excellent reliability. Ideal for ventilation, light deprivation and blackout systems.
24 volt DC motor, comes with built in limit switches. Torque: 44 Nm RPM: 4.5 Amps: 2 (max: 4) Revolutions : 40 Weight: 3.5 Kg
Both couplers are used with 1-3/8" outside diameter tube.
We provide a list of items (available from a home building centre) necessary for install - or purchase installation kits. Controllers not included.

*A netwon metre is a unit of torque in the metric system. 44nM = 32.453 ft-lb.