Do Indoor Plants Reduce the Temperature of the Room?

Do indoor plants reduce the temperature of the room

Indoor plants add beauty and style to indoors. But they also have an ecological benefit for indoor air.

They improve the quality of air by releasing oxygen and absorbing carbon dioxide and other pollutants found in the home. In addition to this, plants help to reduce the temperature of the air indoors.

Let us delve into details for a finer understanding of how do plants make the room cooler

How House Plants reduce the temperature Indoors

According to NASA’s earth science study, plants can alter the temperature of the earth’s atmosphere through a process called photosynthesis. Plants produce large amounts of transpiration that increase water vapor in the atmosphere causing more precipitation.

The uptake of water at the roots, transport of water through the plant tissues and release of water vapor by leaves is called transpiration.

Cooling is doubled in areas such as forest canopies which blocks sunlight. Potted plants function in much the same manner as huge trees.

According to Dr. Williams, from the Melbourne school of land and environment, from the University of Melbourne, “ plants are attractive, natural air conditioners. They should be used in large amounts to cool as they evaporate water through their leaves into the atmosphere.

Indoor plants keep the house cooler indoors in summers. When the atmosphere heats up, plants release excess water into the air from their leaves, and by releasing evaporated water, plants cool themselves and the surrounding environment. They release water through pores called stomata in their leaves.

This process of transpiration cools the plant, just as perspiration cools human beings. The blocking of sunlight indoors reinforces this coolness.

The moisture released by indoor plants helps maintain indoor humidity in the human comfort zone of 30-60 percent.

According to the University of Vermont Extension, plants kept in a warm room release moisture into the air and can reduce the temperature as much as 10 degrees.

So yes, indoor plants do help to reduce the temperature. The more the plants, the larger the surface area, the more the transpiration. This leads to a cooler indoors.

In winters, on the other hand, as plants add humidity to a room, and so the room feels warmer. This is because moist air holds heat better.

Some researchers claim transpiration as a natural byproduct of photosynthesis which cannot be avoided. According to them when there is a gaseous exchange between the plant and atmosphere, the stomata pores open up and the water transpiration takes place as an unavoidable phenomenon that accompanies the real function of stomata.

How the stomata pores work

Once the photosynthesis process starts a signal is given to the guard cell plasma membrane to start pumping protons out of the guard cells. Potassium ions enter the guard cells and accumulate causing the solute potential to be lowered.

A lower solute potential attracts water to enter the cell. As water enters the guard cell, its hydrostatic pressure increases. The pressure causes the shape of the guard cells to change and a pore is formed, allowing gas exchange and at the same time allows the exit of water vapor.

Stomata must be open for the plant to photosynthesize, however open stomata present a risk of losing too much water through transpiration. Stomata close when the guard cells lose water and become flaccid.

How much water do plants transpire? 

Plant transpiration is pretty much an invisible process. Since the water is evaporating from the leaf surfaces, one cannot see the leaves transpiring. But that does not mean that water is not being given off to the air.

One easy method to visualize transpiration is to put a plastic bag around some plant leaves. The transpired water will condense on the inside of the bag.

During the growing season ( May to September), a leaf will transpire many times more water than its own weight.

Factors affecting transpiration and thus affecting a reduction in temperature

  • The temperature of the atmospheric air indoors affects the transpiration process of the houseplants. Higher temperatures cause the stomata pores to open up and give off more water to the atmosphere. Colder temperature causes the stomata pores to close.
  •  As the relative humidity of the air surrounding the plant rises, the transpiration rate falls. It is easier for water to evaporate into drier air than into more saturated air. That’s why when it is raining outside the plants don’t transpire a lot of water indoors as relative humidity is already high
  • Increased air and wind movement around the plants will increase the transpiration rate. That is because the air is moved around and the saturated air is moved away from underneath the leaves and drier air comes in. This will create a cool atmosphere in the potted plant room. The drier the air around the plants, the greater is the driving force for the water to move through the plant and the faster is the transpiration rate.
  •  Soil moisture availability affects the transpiration process. When moisture is lacking, plants begin to senesce ( premature aging which can also lead to leaf loss) and transpire less water. Similarly, darkness causes the stomata pores to close.
  • Different plants transpire water at different rates. Plants that grow in arid regions such as cacti and succulents conserve water and transpire less compared to other houseplants. Many plants have stomata only on their lower surface to help avoid water loss. Some plants have many hairs on their leaf surfaces which reduce the rate of transpiration. Sun-loving plants have thicker cuticles than shade-loving plants causing slower rates of transpiration.

Indoor Plants that reduce Temperature

Here are some of the indoor plants that can reduce the temperature and keep your indoors cool

Ficus Benjamina 

These are one of the few trees that grow well indoors. It is also known as weeping fig. It helps to keep the air inside moist and cool. Ficus grows well in medium light.

It loves to be grouped with other houseplants and drinks more. Make sure to keep it watered.

Ficus elastica (rubber plant) 

Rubber plant has a cooling effect and improves room humidity by replenishing the moisture in the air. The more foliage it has, the bigger the leaves are, the more moisture it will release back into the air.

Give it small sips of water so that the soil remains evenly damp and place it in a light spot but not direct sunlight.

Chinese evergreen (Aglaonema) 

Chinese evergreen has a high transpiration rate that helps humidify the air around it. It is also well known for its ability to purify toxins in the air. It is a low maintenance plant and ideal for indoor settings requiring low light and less water.

Mother in law’s tongue (Snake plant) 

The leaves of mother-in law’s tongue plant (Snake Plant) have a high water content, so when it transpires, it releases cool evaporated moisture into the air. It also gives off oxygen keeping you cool and fresh.

It is known for removing toxins from the air like formaldehyde and benzene. It has a cooling effect on the room and also provides shade for other plants.


The green leaves of the areca palm, fern palm, fishtail palm and lady palm act as natural humidifiers. They are also helpful in removing indoor pollutants like benzene and formaldehyde. While selecting areca palm, go for a palm with a thicker trunk at the base.

Some other excellent natural humidifiers which reduce the temperatures are Boston ferns ( they also happen to have good air-purifying qualities), Aloe vera ( they require a good amount of sunlight so keep in a sunlit area), golden pothos (with best air-purifying qualities).

Syngonium, peace lilies, anthuriums, and spider plants also have a good humidifier and air purification qualities.


With all these plants, bring the temperature down and enjoy the coolness and freshness of well-aerated indoor accommodation.

It is a natural and inexpensive way to reduce the temperature and keep your house cool. Consider getting 12-15 of the plants mentioned above which can help keep the temperature down.

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