Summer climate control
Keep your greenhouse cool, productive, and hydrated all summer long
Combine shading, ventilation, evaporative cooling, and moisture management to defend plants against heat stress and prevent yield losses.
Choose and install shade cloth for maximum impact
Shade cloth reduces solar gain, lowers plant leaf temperature, and slows evaporation. Select the right density and install before the first major heat spike.
| Structure type | Recommended shade cloth | Seasonal deployment |
|---|---|---|
| Glass greenhouse | 70% UV-stabilised cloth | Install late May, remove early September |
| Polycarbonate greenhouse | 60% cloth or reflective whitewash | Install when interior peaks >86°F (30°C) |
| Hoop house | 50–60% knitted cloth with roll-up option | Deploy in hot spells, retract on overcast days |
Secure cloth with clips or wire tracks. Leave 6–12 inches at the base for airflow, and consider removable panels for quick venting after storms.
Ventilation is your first cooling layer
Start with natural airflow and add mechanical systems as temperatures climb. Properly sized vents and fans prevent heat accumulation around the canopy.
Maximise vent area
Ensure combined roof and side vents equal 15–20% of floor area. Add automatic openers so vents respond the moment interior air hits 80°F (27°C).
Layer mechanical airflow
Use thermostatically controlled exhaust fans paired with motorised intake shutters. Set activation temperatures to 82°F (28°C) with a 3°F differential.
Maintain circulation
Run horizontal airflow fans 24/7 to eliminate stagnant pockets. Aim for gentle air speeds (50–100 ft/min) through the canopy.
Need detailed vent ratios? Review the ventilation management guide for sizing formulas and maintenance checklists.
Evaporative cooling and misting strategies
- • Install foggers or misters above the crop canopy and run in 1–2 minute bursts to drop air temperature without saturating foliage.
- • Use evaporative pads on the windward side and exhaust fans on the leeward side to pull cooled air through the greenhouse.
- • Drain and sanitise evaporative systems monthly to prevent algae, scale buildup, and pathogen reservoirs.
- • Combine evaporative cooling with shade cloth to reduce water consumption by 10–15%.
Keep relative humidity between 55–75%. If humidity rises above 80%, increase ventilation or shorten misting cycles to avoid disease pressure.
Watering, mulching, and crop care in extreme heat
Plants respire heavily when heat spikes. Support them with thoughtful watering, pruning, and crop arrangement.
- • Increase irrigation frequency in raised beds and containers; drip systems minimise leaf wetness.
- • Apply light-coloured mulch or reflective ground cover to reduce soil temperatures.
- • Prune dense foliage on tomatoes and cucumbers to improve airflow without exposing fruit to sunscald.
- • Stage heat-tolerant greens (Swiss chard, Malabar spinach) under trellised crops to utilise partial shade.
Monitoring and maintenance
- • Position digital temperature and humidity sensors at plant height in at least three zones.
- • Set SMS or app alerts for temperatures above 90°F (32°C) or humidity above 85%.
- • Keep a log of daily maximum/minimum temperatures to adjust shading and ventilation thresholds.
- • Check fan belts, louvers, and vent hinges weekly for dust or mechanical wear.
Next actions
- Audit current shade, venting, and fan capacity; upgrade before the first sustained heat wave.
- Install remote sensors or integrate existing monitors with alerts for on-the-go response.
- Schedule monthly maintenance for cooling equipment and document parts that require replacement.
Frequently Asked Questions
What shade cloth percentage should I use?
Glass houses typically need 70% cloth, polycarbonate structures 60%, and hoop houses 50–60%. Select UV-stabilised material and secure with grommets every two feet to prevent wind damage.
Can I rely on ventilation alone?
Ventilation is essential but often insufficient during prolonged heat waves. Layer shade, mechanical airflow, and evaporative cooling so temperature stays below 86°F (30°C).
How often should I water in peak summer?
Monitor soil moisture daily. Water deeply in the morning, use mulches to conserve moisture, and add afternoon misting if leaf temperatures exceed ambient air.