DRAWING THE SHEET —
DRAWING THE SHEET —
ENVIRONMENTAL SYSTEMS — THE ACTIVE PATH
The house ships sealed, and this package opens it at two points. Exhaust fans on the door end pull outside air through the wet pad at the back, then the stream crosses every foot of the crop on its way out. At full pull it turns over the house's entire air volume every 2 to 3 minutes.
FAN ENDWALL + WET-WALL ENDWALL TINTED BLUE — ILLUSTRATIVE · DRAG TO SPIN
ONE PACKAGE — $5,000 ON A 30×100 BAY, FROM THE BOOK
01 — THE PACKAGE — ENGINEERED TO THE SIZE OF THE HOUSE
We size the package to the house you build. The circulation-fan count steps up with length, and the book price steps with it.
3 EXHAUST FANS
On the door-side endwall, pulling air the length of the house.
1 WET WALL
The evaporative pad across the back endwall. Air cools as it comes through.
6 VENTS
5 at the wet wall + 1 up on the ridge.
4 / 6 / 8 CIRCULATION FANS
At 60 / 80 / 100 ft. Canopy air keeps moving between exchanges.
$4,000 AT 60 FT + $500 PER 20 FT BEYOND, PER BAY — THE BOOK'S VENTILATION LINE, SIZED TO LENGTH
02 — THE AIR PATH — FANS PULL, THE PAD COOLS
ONE DIRECTION, EVERY FOOT
The fans lower the pressure at the door end, so outside air has one way in: through the wet pad, where evaporation cools it before it crosses the crop.
03 — WHAT EVAPORATION CAN AND CAN'T DO
COOLS TOWARD WET-BULB
Up to ~85% evaporative efficiency.
STRONG IN DRY HEAT
90°F at 30% humidity cools to roughly 67°F.
WEAKER IN HUMID AIR
90°F at 70% humidity reaches about 82°F.
TRACKS THE OUTSIDE WET-BULB
The supply air follows the weather. A held setpoint takes the VPD system.
SOURCE — UMASS EXTENSION (FAN & PAD) · ACES/AUBURN
IF YOUR DESIGN DAY IS HOT AND HUMID — VPD CONTROL
04 — CHOOSE
You've seen what the package does and where evaporation stops.
Answer it the way your worst week goes. If the active-ventilation package holds your numbers, we'd rather you keep the money.
THE DECISIVE QUESTION
On your hottest, most humid design day, can outside air pulled through a wet pad still hold the temperature and humidity your crop needs?
IF YOU'RE WEIGHING IT ON CLIMATE
LEAN ACTIVE WHEN —
Dry heat. Evaporative cooling drops the most degrees where humidity is low
LEAN VPD CONTROL WHEN —
Your design day is hot and humid
IF YOU'RE WEIGHING IT ON CROP
LEAN ACTIVE WHEN —
Leafy greens, cool-season veg, hardy ornamentals, nursery and bedding stock
LEAN VPD CONTROL WHEN —
High-value fruiting, propagation, disease-sensitive crops, cannabis
IF YOU'RE WEIGHING IT ON QUALITY BAR
LEAN ACTIVE WHEN —
Healthy and marketable, seasonal, weather-tolerant
LEAN VPD CONTROL WHEN —
Contract-grade consistency, max yield per square foot, year-round
Still split? Disease usually decides it. When one humid night of bud rot or powdery mildew costs more than the climate equipment, size the VPD system. Otherwise buy the active-ventilation package and bank the difference.
The build tool sizes it to your length and prices it live on your exact configuration.