How to Insulate Your Greenhouse for a Thriving Winter Garden

Have you ever imagined plucking fresh herbs while the snow falls outside?

Are you eager to transform your DIY greenhouse kit into a winter-proofed paradise?

Discover the ins and outs of effective insulation to keep your greenhouse garden flourishing all winter long.

While Planta's Polycarbonate greenhouses are already designed with superior insulation, a few clever tweaks can enhance the warmth factor for your plants during the chilly months.

Curious about the best insulation for a DIY greenhouse for beginner gardeners? Dive into our comprehensive guide, filled with all the essential tips and tricks for fortifying your greenhouse against the cold – ensuring a vibrant, cozy sanctuary for your plants throughout the winter season.

Why Should You Insulate Your Greenhouse?

Insulating your greenhouse is like wrapping your favorite winter scarf around your neck; it’s essential for comfort and protection. The best greenhouse insulation maintains a warm, steady climate for your plants, making your heater more effective and energy-efficient.

It's not just about keeping the cold out; it's about creating an environment where your greenery can thrive despite the snow outside.

When Should You Start Insulating?

Don’t wait until winter is on your doorstep. Start insulating your greenhouse when the evenings cool down and the autumn leaves have started falling off the trees. Ensure to insulate before the first frost so your plants stay blissfully unaware of the weather outside.

7 Effective Greenhouse Insulation Ideas

  • Seal up Gaps and Cracks

Seal up any sneaky drafts with silicone caulk – a simple yet effective fix for those tiny gaps where cold air loves to seep in. This keeps the warmth wrapped inside, making your heater's job easier and less costly.

  • Harness Thermal Mass

Fill up barrels or large jugs with water, or gather some rocks and place them around your greenhouse. These will become your very own sun sponges, absorbing daytime warmth and gently radiating it back during the cooler nights, keeping the space pleasantly warm.

Watch from 4:18 to learn how Planta Greenhouse owner Cara Coad, uses thermal mass to keep her greenhouse insulated through winter.

  • Attach Door Sweeps and Curtains

Cold air loves to slip in under doors. Fix this by attaching sweeps (long brush-like strips) to the bottoms of your doors. For even more warmth, hang some heavy curtains over your doors to double up on insulation.

  • Apply Reflective Materials

Bring a sparkle to your greenhouse by applying shiny aluminum foil to the interior. This simple trick reflects extra light onto your leafy friends, giving them a bonus helping of sunshine while helping to hold in the heat.


  • Bundle up with Bubble Wrap

Bubble wrap's air pockets are fantastic insulators. Line the interior of your greenhouse with it, and you’ll maintain a stable temperature without cutting down on that precious winter sunlight for your plants.

  • Insulate the Foundation

It's not just the air you need to worry about – cold comes from the ground, too. Line your foundation with foam boards or a layer of straw to prevent cold from creeping in from the ground up. Alternatively, pea gravel or stones can be a visually appealing and practical choice – capturing the day's warmth and gradually releasing it, warming up your greenhouse as night falls.


  • Generate Heat with Compost

Indoor composting in your greenhouse is a dual-purpose win: it recycles your garden scraps while giving off a natural warmth as it breaks down. This method requires some extra care, but it rewards you with a cozy temperature boost for those chilly days and lush, nutrient-packed soil ready for spring planting.

When to Remove Greenhouse Insulation

Knowing when to remove greenhouse insulation is just as important as putting it up. The ideal time to peel back the layers is when the risk of frost has passed, and daylight has begun to stretch into the evenings. Keep a close eye on temperature forecasts; removing insulation too late can lead to overheating and wilted plants.

Keep Your Garden Flourishing All Winter Long

Give your greenhouse some extra insulation this chilly season, and watch it transform into a toasty haven for your leafy companions. This savvy move reduces your energy footprint and eases the workload on your heater.

The reward? A gently heated space where your plants can grow all winter long.

Eager for more cold-weather gardening tips? We've got a treasure trove of advice on getting your greenhouse ready for winter, protecting your soil from frost, and tips & tricks to keep your botanical buddies happy until spring.

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