How-to Guide
Cooling and Shading a Greenhouse in Summer
The short answer
Ventilation alone often cannot control greenhouse temperature on hot, sunny days, so summer cooling combines air exchange with shading and, if needed, evaporative cooling. Natural roof and side vents or exhaust fans move heat out, while shade cloth or a liquid shading compound cuts the incoming solar radiation that drives temperatures up.
For shade to help, it should be porous or placed outside the glazing so trapped heat can escape; exterior shade intercepts sunlight before it enters and cools more effectively than interior shade. On the hottest days, a fog or evaporative cooling system adds further cooling.
Ventilate first
Move heat out with roof and side vents or exhaust fans. A well-designed fan-cooled house provides ample summer air exchange to keep temperatures manageable, but ventilation by itself is often not enough in peak summer.
Add shade
Reduce incoming light with shade cloth or a liquid shading compound applied to the glazing. Exterior shade blocks sunlight before it enters and cools better than interior shade; interior shade should be porous so heat can rise and escape.
✔ On very hot days, evaporative or fog cooling can supplement ventilation and shade for further temperature reduction.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- UMass Amherst Extension Greenhouse & Floriculture — Shade for Cooling Greenhouses — Porous or exterior shade cloth and shading compounds reduce greenhouse heat.
- UMass Amherst Extension Greenhouse & Floriculture — Ventilation for Greenhouses — Fan ventilation capacity for summer cooling and its limits.
- UMass Amherst Extension Greenhouse & Floriculture — Natural Ventilation in Greenhouses — Roof and side vents exchange air to cool greenhouses naturally.
Keep going
Protecting the Garden from Frost (and Stretching the Fall Harvest)
Seasonal Action Guide
How to Use a Cold Frame
How-to Guide
Season Extension Methods: Cold Frames, Row Covers, Cloches, and Tunnels
Reference
Cold Frame vs Hoop House vs Greenhouse
How to Heat and Ventilate a Greenhouse in Winter
How-to Guide
Cyclamen Care: Cool Rooms, Bottom Watering, and the Summer Rest
How-to Guide
How to Grow a Fine Fescue Lawn
How-to Guide
How to Grow Mustard Greens: Fast, Cool, and Gone by Summer
How-to Guide