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heating greenhouse with water barrels

Way of heating Greenhouse With Water Barrels: Thermal Mass Greenhouse

We often use electricity as a primary source to heat the internal area of greenhouses during the winter. But how about using a natural option? One of the most common items is utilizing water barrels.Water drums will cover a small or moderate portion of space in your greenhouse. But they are eco-friendly and affordable. You don’t need to bear as much cost as you do with electric heaters or similar items.But knowing how to heat a greenhouse with water drums is important. You have to consider where to put it and how many drums you will need as per your greenhouse size.Here, we will go for an in-depth discussion on heating greenhouse with water barrels step-by-step. Just stick with us. Read until we finish.

Heating Greenhouse With Water Barrels Step By Step

Our vulnerable greenhouse plants often suffer a real loss due to the weather. Ensuring a proper warm environment during the winter night is necessary. Here are the steps you can go through to heat your greenhouse with water barrels.

Step 1: Choosing the right water barrels 

Step 1_ Choosing the right water barrels

You can use some 55-gallon barrels as a thermal mass in your greenhouse. They are mainly utilized for water storage. Compared to other solutions, water barrels are more effective and affordable options.These water barrels are filled with a point five percent disinfectant solution to make them appropriate for water storage or garden water. More importantly, it doesn’t have any harsh chemicals. They are available in various dimensions and hues. But black ones are more appropriate to be used as a heat sink. They will absorb the energy from the sun more readily than white ones or blue ones. They have a nice shape as well. If your greenhouse height is not standard, you may struggle slightly to install 55-gallon water barrels. In such as case, choose barrels with a wider body. But this will cover more space inside the greenhouse. You can check the grain barrel from the below list also (#Ads)

Step 2: Selecting Appropriate direction for Water Barrels 

Step 2_ Selecting Appropriate direction for Water Barrels

You can keep them outside the green during the day before finally installing them inside the greenhouse. Just line up them. Determining on which side to keep the water drums is a crucial thing to consider. This is really a good opportunity to reevaluate the layout and see how you can maximize the use of space. Generally, we recommend lining up drums of water on the west side. They will get a nice time during the day to heat them and do the best job for what you are looking for.

Step 3 : Preparing the Greenhouse Ground Level 

Step 3 _ Preparing the Greenhouse Ground Level

Before finally placing the barrels or gallons of water inside the greenhouse, properly level the ground. Get rid of all the dirt and other unwanted things from the path. This will ensure a great stand. You can also clean the internal area of the water barrel using hot, soapy water. Then, wash them with normal water. Keeping the internal area clean will improve its hit retaining capacity too. Now, put the barrels in a row. They will look pretty neat and organized.

Step 4 : Filling the Water Container 

Step 4 _ Filling the Water Container

Fill up the container with water and then monitor low temperature and other things. This will now hopefully regulate the temperature efficiently. Keeping the barrel in the western wall gives a benefit. The afternoon sun will heat these water drums from a particular direction. The heat will be released at night. So the point of the barrels is not only to dissipate or give off heat when it’s cold outside but when it’s warm out to absorb the heat.If you touch the outside surface, you will notice they are sweating. The reason is that the internal area is warm. You will feel cool to touch them.At night, what’s cool to the touch now will be warm. They will release that heat back into your greenhouse.

Step 5: Refilling the Water Barrel Regularly 

It is a solid rule of thumb to inspect the water level regularly. Refill the container if it gets low. The more water you keep, the more heat energy it can store and release at night.

What is Thermal Mass and how it Work

What is Thermal Mass and how it Work

Our greenhouse plants struggle to keep them in a decent condition at the time of winter. A thermal mass is one type of product or material that takes advantage of the heat that builds up during the day.This will somehow hold on to that heat store. That heat is to be released later on at night to help heat our greenhouse.

How Thermal Mass Works

The thermal process working process is pretty simple. You don’t need to put anything together. No electrical controls or timers are needed. There is nothing involved.You just fill a barrel with the water. Set it in the greenhouse. But it heats up during the day. And then that heat will be released back at night. That’s a passive solar heating system.

Why Is Thermal Mass Important

Thermal mass is a great way to improve the internal condition of our greenhouse. Its main job is to create a comfortable temperature for the greenhouse plants so that they can live better.

But some crucial points need to consider setting up a particular thermal mass. Airtightness, solar access, insulation levels, climate zone, etc., are some of the most important factors to consider.

How Many Water Barrels Does It Take To Heat A Greenhouse

The number of water barrels you will need mainly depends on your greenhouse size and how lower the temperature is.Since our greenhouse sizes vary, the number of water barrels will also be different. Generally, we have either small, medium or large greenhouses.Here we mention three standard greenhouse sizes and how many water barrels we will need. You can also check the black water barrel price from the below list…(#Ads)

Greenhouse Type Number Of 55-Gallon Water Barrels Needed
Small Greenhouse (6×8) 2 or 3
Medium Greenhouse(8×12) 4 or 5
Large Greenhouse(10×16) 7 or 8

How to Calculate Number of 55-Gallon Water Barrels

You may feel a little bit confused about how we have determined the number of 55-gallon water barrels.At first, you need to multiply the wide-area and long area of your greenhouse. This will aid you in determining the square footage of the greenhouse.

For example, your greenhouse width and length is 8×12. So, the multiplication result is 96.Now, you want to again multiply the result by 2.5. This can assist you in determining the number of gallons of water to heat the greenhouse properly. The result for this example will be 240 gallons.Next, divide the result by 55 to determine the number of 55-gallon water barrels you will need. In this case, the result is 4.36. Hence, you can keep 4 or 5 water barrels.

Consider the Temperature Condition

When you live in an extremely cold climate, you will need to cover more space of your greenhouse with water barrels to keep it heated and usable.

But you can follow our calculation approach to find the correct number of water barrels for a moderately cold climate.Another important thing is not overheating the greenhouse plants. This will cause humidity issues and controlling the humidity inside greenhouse is also important . Otherwise, it may lead to the germination of fungal pathogen spores or rot issues.

What Is The Best Material For Thermal Mass

Though you can use a wide range of materials for thermal mass, water is the best suitable option.

Stone floor or wall

Apart from water, people can use building walls of stone or stone floors. They will work great too.


Wood is another eco-friendly choice. As far as the effectiveness of materials as heat sinks, wood is about the lowest. But wood is a natural option.

According to experts, water is three times better than concrete, rocks, or stone and six times better than wood.

Why Water Is The Best Material For Thermal Mass

When comparing water with other materials, you need to consider the space it will occupy inside the greenhouse. After all, utilizing each inch of the space should be your main priority.A 55-gallon drum of water can approximately hold as much as seven cubic feet of concrete or rocks. Simply put, two gallons of water will be the equivalent of 80 pounds of rock. So, the size of a container matter. A small water container can do so much more than a huge pile of rocks. Water is a great heat sink. You can line it the entire north wall of your greenhouse. On the contrary, you will have to fill the entire greenhouse with rocks just to get the same effect as that one wall of barrels.

How Water Works More Effectively To Retain Heat

How Water Works More Effectively To Retain Heat

Generally, the store heating capacity of a particular material is determined by volumetric heat capacity (VHC). Water has the maximum VHC. In order to raise 1°C of a particular material, water can utilize 4186 kilojoules (kJ) of energy. But other materials like concrete, stone, compressed earth blocks, brick, etc., have a less than 2000 kilojoules (kJ) rating.So, it is not hard to see why you should use water over materials as the best thermal mass. They have massive heat absorption capacity and can retain the heat for a prolonged period to heat the greenhouse plants.


How do you increase the thermal mass of a greenhouse?

Water barrels are an effective choice to raise the thermal mass of any type of greenhouse. Water has the maximum amount of heat-retaining capacity compared to other materials. But you need to allow them to stay in the sunlight direction. The higher sunlight they capture, the more heat they release at night.

Can we rain barrel to heat greenhouse?

Yes, you can use your rain barrel to heat your greenhouse. It is an innovative approach to take care of your greenhouse plants. But dark black walls are a better choice to conserve more energy. Additionally, they will add a better appearance to your greenhouse while directly collecting water from the rain.

Where to place the water barrel?

It is a good rule of thumb to place the water barrel in a particular direction and location where it can get the maximum amount of sunlight. The sunlight it gets, the more energy it can consume. You may need to elevate the water barrel position when the drum is not getting enough sunlight from a particular spot.

How much time its take to heat a greenhouse using water barrel?

Generally, your greenhouse should have at least 6 hours of full sunlight each day to receive enough heat. Extended heat appears better if the weather is extremely cold at night. The colder the weather at night, the more heat your greenhouse plants need. In such a case, additional hours of sunlight will be better.

What material water barrel is best to heat the greenhouse?

Water barrels are mainly available in plastic or metal form. Compared to plastic, metal water barrels are more effective in retaining heat for an additional time. But plastic barrels are a significantly low-cost option. In addition, they are more prone to have rust or corrosion if the internal metal quality is cheap.


Heating your greenhouse plants is necessary during the growing season. Their growth will be affected by extremely cold weather. So, the more optimal heat you can provide, the better natural growth they will have. Heating greenhouse with water barrels requires considering some important factors. You have to choose the right size water barrels, enough number of water barrels, and set up in an ideal location and direction.Hopefully, you got a descriptive idea of how to set up water barrels in a greenhouse step-by-step and how heating greenhouse with water barrels work . Make sure to consider your weather condition, and refill the water container regularly for better heat retention.

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