If your greenhouse freezes overnight, the first step is to check the temperature inside and assess the damage to your plants. If the temperature drops below freezing, you’ll want to increase insulation as much as possible by covering plants with row covers or blankets. If you don't have thermal mass like water barrels, consider adding some to help regulate temperature during the night.
Opening vents or windows during the day can help warm up the greenhouse, but be sure to close them before nightfall to trap heat inside. To prevent future freezing, ensure your greenhouse is properly sealed and insulated, using bubble wrap or double glazing on the windows. It’s also important to monitor the weather and take precautionary measures before especially cold nights, such as moving more vulnerable plants into insulated areas or using a portable heater.
