Do Greenhouses Need to Be Airtight?

Growing plants in a greenhouse means providing all the right conditions for thriving fruits and vegetables. But is airtightness one of those conditions?

Do greenhouses need to be airtight? Yes, your greenhouse should be airtight. This will keep the heat in, especially during colder months and during the night. However, you also want to have vents that can allow fresh air to get in if temperatures get too high during summer.  

If this answer is complicated — don’t worry. Read on and learn all about greenhouses, whether to make them airtight or not, how to seal them for the winter, and create optimal conditions for plant growth. 

Why Is It Important for a Greenhouse to Be Airtight? 

Now that you know how a greenhouse works, you can understand why airtightness is so important. While your plants get plenty of light and heat during the day, nights get too cold, no matter how hot the summer is. Especially some tropical plants that need the conditions to match their original climates. 

Furthermore, colder days happen even in the midst of a blazing summer, so you have to keep in mind that your plants will need care then too. Not to mention that winters, in some areas, in particular, are too cold for most plants. If you want consistent growth throughout the year, you need to enable them the best conditions for that. 

If your greenhouse is airtight, it will keep the warmth more efficiently. Especially so if you have heaters inside — you don’t want to waste money heating the outdoors. 

Naturally, you need to know when to let the fresh air in, but you can do that through vents, and most likely during summer. Keep in mind that you should still vent the greenhouse during winter. Stale air leads to mold, so provide your plants with some fresh air by opening a vent or turning a fan on. 

How to Seal a Greenhouse?

With insulation and sealing, your greenhouse will be airtight, and your plants will be safe from cold and weather conditions. Sealing a greenhouse properly can also prevent pests from getting in. 

For starters, you should caulk around the bottom — the foundation — of your greenhouse. This is where most gaps can happen, and caulking can help those gaps close, preventing the heat from getting out. Glass greenhouses usually have frames — similar to windows — so sealing around the frames and where glass connects with the frame will help too. 

If your greenhouse is of the curtain type, it might be a bit harder to seal it for the winter. However, during the summer, you can simply press the curtain parts down with something heavy, such as a big rock, a block, a piece of wood, or anything sturdy that can keep it down. 

You can also add Velcro to the frame of a greenhouse and attach the two curtains together that way.

How Do Greenhouses Work? 

A greenhouse is an excellent way to grow plants throughout the year, no matter the season or the conditions outside. It’s usually used by large farms, but regular people also often have them in their backyards. 

They can allow you to have plants which are normally not found in your area — or part of the world even. But the key to having an efficient greenhouse is to understand how a greenhouse works.

For one, they trap warmth and light, which is what most tasty fruits and vegetables need — in addition to water, air, and nutritious soil. However, the latter are all easy to provide. They are available throughout the year in most areas of the world. But what’s usually lacking is the availability of the summer warmth and light. 

Naturally, some plants can survive in all sorts of conditions, but most plants prefer warmth. This is what a greenhouse can give you. Water, air, and soil are your job, but you would do that anyway, wherever you might decide to grow your plants. 

The start of the greenhouse process is the light coming in. So, naturally, you need a way for the light to get in. This is why most greenhouses you see are made of glass or see-through materials. The plants inside get the most out of the daily sunlight hours this way. 

Naturally, plants and everything else in the greenhouse will absorb that light and convert it to heat. But, this heat can’t escape the greenhouse so easily — it’s different than just light from the sun. 

Because the heat stays in, the greenhouse gets warmer. This is where it’s a good idea to have an airtight greenhouse — the heat can’t escape. The temperature will rise as much as possible throughout the day. In fact, most of the time, a greenhouse will be a lot warmer than the outdoor space, even in summer. 

But, during summer, you’ll need to find a way to lower the temperature in the greenhouse. The airtightness of the outer walls is important, but so are vents when necessary. You probably won’t use them at all during winter. However, during summer, a high temperature can kill the plants. 

For optimal results, keep your greenhouse in a space that gets plenty of sunlight. Of course, greenhouses work the best in parts of the earth that don’t get many cloudy days. 

When your plants get enough sunlight and warmth, they will perform photosynthesis. If you want a good rate of growth, you should ensure that they get at least 6 hours of sun. Naturally, check with a professional whether your specific crops need that much. 

The glass or plastic that makes a greenhouse is great for sunlight but bad for keeping the heat inside. You may not notice this on hot days, but as soon as it gets colder, you’ll be able to tell. If your plants are vulnerable to colder temperatures, plan ahead, and get materials that can seal your greenhouse. 

You can also get an artificial source of light or heat — or both — for colder days and possibly even nights. 

For keeping the heat in, you may want to use a high-density material somewhere within your greenhouse. An easy solution could be stone or brick for pathways or floorings inside the greenhouse. They will make the heating process in your greenhouse slower, but they will also take a lot longer to cool down, and they will possibly release the heat gathered throughout the day slowly through the night. 

Another possible solution is to put a larger amount of water into your greenhouse. This could be a barrel — but it’s better if the material of the container is see-through — full of water. Some greenhouse owners have come up with the idea of placing fish tanks in the greenhouse. It adds to the look, you can use the waste from them as a fertilizer, and water releases warmth slowly too. 

Finally, you can also heat your greenhouse with artificial heat, especially in the winter. An ideal answer is to have a heating system that connects to a thermostat and turns it off once the desired temperature has been achieved or turns it on when necessary. 

Keep in mind that plants will spend more nutrients in the greenhouse than if they were grown outside, so you’ll have to take good care of them if you want to keep them healthy. Just sun and warmth won’t work. You’ll need to fertilize more often, use vents to give them some fresh air, water them often (water evaporates quickly in the sun), etc. 

Final Thoughts

So, your greenhouse should definitely be airtight. However, you should also ensure that there’s plenty of fresh air for the plants to grow healthy, as well as water, nutrients, etc. Seal your greenhouse as soon as you put it up, but also check up on it occasionally, so you don’t miss any cracks. 

Make it a point to go around the greenhouse at least once a month and check for holes or similar areas. Then, caulk them up or seal them in a different way. You can also find out where the heat is leaving your greenhouse by moving your hands across the panels and see where the air gets colder. 

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