How to Seal Your Greenhouse


The proper sealing and insulating of your greenhouse protects the plants inside from a variety of potential hazards. During the winter months, a good seal keeps the cold air from leaking in and causing a possible freeze. Throughout the rest of the year, the seal on your greenhouse can prevent large pests from getting in and prevent the warm air circulating through the greenhouse from escaping.

Step 1

Check the caulking around the foundation of any type of greenhouse. The gaps where the frame of the greenhouse and the foundation meet should be caulked upon installation. If you have a glass greenhouse, fill in any gaps or holes in the frame with caulking to seal the greenhouse.

Step 2

Hold the bottom of the plastic down in curtain-style greenhouses with a heavy block of wood or piece of metal on each side. Purchase a piece of metal the same length as the side so that the metal reaches across the entire bottom, or cut a block of wood the same length as the side so that it fits across the bottom. Fold the bottom of the curtain inward so that the bottom lies on the ground, and place the metal or wood across the bottom to seal it against the ground.

Step 3

Install Velcro strips on the frame of curtain-style plastic greenhouses. Run the Velcro strips down the entire length of each vertical corner post in the greenhouse frame. Leave the two halves of the Velcro strips attached to each other when sticking the strips to the frame.

Step 4

Peel off the backing on the exposed side of the Velcro strips, one at a time, and press the plastic curtains against the adhesive backing. Put pressure on the plastic until it sticks to the Velcro strip from the top to the bottom. To open the plastic curtains, peel the Velcro apart.

Tips and Warnings

  • Do not seal your greenhouse airtight, even during the winter months. Leave the greenhouse vents open for air circulation. Closing off the greenhouse completely leads to mold and mildew, which can kill the plants inside. In freezing temperatures, you can close the events overnight to help prevent frost.

Things You'll Need

  • Caulk
  • Metal or wood blocks
  • Velcro strips


  • Sherry’s Greenhouse: Greenhouse Winter Preparation
  • University of Massachusetts Extension: Natural Ventilation in Hoophouses
Keywords: winter sealing greenhouse, plastic curtain greenhouse, glass greenhouse sealing

About this Author

Alexis Lawrence is a freelance writer, filmmaker and photographer with extensive experience in digital video, book publishing and graphic design. An avid traveler, Lawrence has visited at least 10 cities on each inhabitable continent. She has attended several universities and holds a Bachelor of Science in English.