Role of Houseplants in enhancing IES ‘Indoor Environmental Status’

Houseplants are prettier, cheaper and quieter than electronic filters. Choosing pollution-busting plants is simple: the larger the leaf, the more impurities it absorbs. Aim should be for 2 to 3 large-sized plants per 100 sq ft.

Now-a-days people live without thinking that there is not any greenery in and around their homes. The residences near the industrial and highway areas demand more vegetation, as they block the pollutants to come inside the homes as well as they generate fresh air to breathe. The things and furnitures in the homes themselves generate several pollutants which can be harmful for general living conditions. Several studies of foreign countries proves the efficiency of plants in air tight glass chambers but the researcher wanted to find out the actual effectiveness of the houseplants in residences with natural living conditions. So, my doctoral study was conducted with the following objectives:

• To collect information on the varieties of common houseplants available in Udaipur
• To standardize the utilization of houseplants and study their impact on indoor environmental status in various areas of the residences.
• To develop the guidelines on “houseplants and their role in improving the environmental status”.

The work on the above objectives was done with the following delimitations:

1. The study was limited only to the selected ground floor sample residences.
2. The study was limited only to air quality measures.
3. All the experiments were done only on the selected plants, viz., foliage plants and succulent plants.
4. The areas of sample residences for conducting experiments were restricted only to drawing room and living/dining room.

METHOD OF INVESTIGATION

Indoor Air Quality in the selected rooms, i.e., drawing rooms and dining / living rooms of the 10 west facing residential buildings along with the National Highway- 8 in polluted zone, was analyzed through its physical, chemical and other characteristics.

1. Physical characteristics of air include:
   • Room temperature
   • Relative humidity
   • Air flow rate
   • SPM (Suspended Particulate Matter) count
2. Chemical characteristics of air include:

Gaseous Analysis-

• Important Component Gas of Fresh Air

• O₂
  • Pollutant Gases like
• CO₂
• SO₂
• NO₂
• VOCs measurement- Benzene, Xylene and Formaldehyde

1. Other Characteristics of air includes:

• Sound level
• Presence of smell/ odour

To measure room temperature, RH and air flow rate, the equipment 4 in 1 Environment Tester was used. The SPM count was measured by Handy air sample. The carbon dioxide was analyzed through Gas probe IAQ monitor. Oxygen  and VOCs were measured by Gas Alert micro 5 PID. The sound level indoors was measured by Sound level meter. In order to be precise in measuring the impact of houseplants on IAQ all of the above mentioned parameters were observed in residences considering the following sub parameters:

• Variation in houseplants
• Placement of houseplants
• Variation in days
• Variation in habits

THE MAJOR FINDINGS OF THE STUDY WERE AS FOLLOWS:

 Physical Characteristics of Air:

Impact of houseplants on Room Temperature in Residential Buildings

• The succulent plants were found to be more effective by reducing the room temperature and bring it closer to air quality standard for temperature (22-24°C) under all the selected variations, as compared to the foliage plants.
• The average mean difference in declining the room temperature increased as the number of houseplants augmented, in both types of plants.
• The average room temperature in all the conditions was found to be higher when no houseplant/s was kept on day one as compared to average room temperature with houseplant/s on day two. Houseplants helped in decreasing the room temperature. Similarly when houseplant/s were removed on day three the average room temperature consequently started rising and reached almost equivalent to day one.
• Succulents’ performance was better in declining the room temperature in opened & closed windows and fan in OFF situation, while foliage plants were found to be effective in reducing the room temperature with fan in ON mode. The best results were found by keeping four succulent plants in drawing room with windows keeping open which reduced the room temperature up to 8.50°C.
• Houseplants regulated the room temperature equally, in both the selected rooms.
• The difference in values of ANOVA, Paired-t and Standard Deviations further proves the credibility of houseplants in reducing the room temperature in their presence on day 2 and increasing the room temperature in their absence on day 3.

Impact of Houseplants on Relative Humidity in Residential Buildings

• The foliage plants were found to be more efficient in regulating the relative humidity in the selected areas of the residential buildings and bringing it much closer to air quality standard for RH (40-60 %) as compared to succulent plants.
• With the increase in number of both types of houseplants, average mean difference in regulating relative humidity also increased.
• The average RH in all the conditions was found to be higher when no houseplant/s was kept on day one as compared to average RH with houseplant/s on day two. Houseplants reduced the RH. Similarly when houseplant/s were removed on day three the average RH consequently raised and reached almost equivalent to day one. The best results were found by keeping four foliage plants in drawing room with windows keeping open which reduced the RH up to 7.92 %.
• Foliage plants proved to be more effective in regulating the RH in opened & closed windows and fan in ON situation, while succulent plants were found to be effective in reducing the relative humidity with fan in OFF mode.
• Houseplants regulated relative humidity, in a similar pattern in both the selected areas of the residential buildings.
• Further, the effectiveness of the houseplants by reducing the RH was proved by calculating the difference in values of ANOVA, Paired-t and Standard Deviations.

 Impact of Houseplants on Air Flow Rate in Residential Buildings

• Foliage plants were found to be more effective in improving the air flow rate of selected areas of the residential buildings.
• Increment in number of both types of houseplants persuaded a rise in average mean differences in air flow rate.
• The average air flow rate in all the conditions was found to be lower when no houseplant/s was kept on day one as compared to average air flow rate with houseplant/s on day two. Houseplants helped in increasing air flow rate. Similarly when houseplant/s were removed on day three the average air flow rate consequently decreased and reached almost equivalent to the air flow rate of day one. The best results were found by keeping two foliage plants in dining/ living room with fan ON condition which increased the air flow rate up to 0.29 m/s.
• Foliage plants were found to be more effective in comparison to succulent plants with opened windows, fan in ON and OFF conditions. Whereas, both types of houseplants were proved worthless in improving the air flow rate in windows when they were closed.
• Houseplants were able to improve the air flow rate in humid summers, in both the selected areas of the residential buildings.
• However, the difference in ANOVA and Paired-t values was found nominal and non-significant, but values of Standard Deviations prove the efficiency that the houseplants do help in increasing the air flow rate indoors.

Impact of Houseplants on SPM in Residential Buildings

• In comparison to foliage plants the succulent plants played more effective role in declining the SPM count of selected areas of the residential buildings.
• The increment in succulent plants helped in reducing SPM count more effectively.
• The average SPM in all the conditions was found to be higher when no houseplant/s was kept on day one as compared to average SPM with houseplant/s on day two by reducing the dust in the indoor air. Similarly when houseplant/s were removed on day three the average SPM consequently raised and reached almost equivalent to day one. The best results were found by keeping four succulent plants in dining / living room with windows keeping close which reduced the SPM count up to 0.0147µg/m³.
• Succulent plants again found to be more impressive as compared to foliage plants in opened windows, closed windows and in fan with OFF situation. While foliage plants were great in reducing the SPM level with fan ON condition.
• Houseplants were able to reduce the SPM count in both the selected areas of the residential buildings.
• The significant difference in values of ANOVA, Paired-t and Standard Deviations, was found in all the subparameters selected for the experiments to judge the efficiency of houseplants by reducing the SPM count in indoor air.

• Chemical Characteristics of Air:

 Gaseous Analysis:

Important Component Gas of Fresh Air:

Impact of Houseplants on Oxygen content in Residential Buildings

• The foliage plants were found to be more efficient under all the variations selected for the purpose of the study, in enhancing the O₂ in indoor air of selected areas of the residential buildings.
• As the number of houseplants increased, the average mean difference in O₂ enhancement also increased.
• The average oxygen level in all the conditions was found to be little less from the standard when no houseplant/s was kept on day one as compared to average oxygen level with houseplant/s on day two. Similarly when houseplant/s were removed on day three the average oxygen level consequently lowered and reached almost equivalent to day one.
• Foliage plants again found to be more impressive in enhancing the oxygen level as compared to succulent plants in opened windows, closed windows and in fan with OFF situation. While succulent plants were great in reducing the oxygen level with fan ON condition. The best results were found by keeping four foliage plants in drawing room with fan OFF condition which enhanced the oxygen level up to 0.16 %.
• Both types of houseplants definitely helped in O₂ enhancement in both the selected areas of the residential buildings.
• There was significant difference in majority of the values of ANOVA and Paired-t and Standard Deviations, under all the selected subparameters except few, but it proves the effectiveness of houseplants in improving the IAQ with special reference to enhance the O₂ concentration in the indoor air.

• Pollutant Gases

Impact of Houseplants on CO₂ Level in Residential Buildings

• The succulent plants were found to be more efficacious in depleting the indoor carbon dioxide level from the selected areas of the residences.
• As the number of houseplants increased the average mean difference in diminishing carbon dioxide level also increased.
• The average CO₂ level in all the conditions was found to be higher when no houseplant/s was kept on day one as compared to average CO₂ level with houseplant/s on day two by reducing the CO₂ level in the indoor air. Similarly when houseplant/s were removed on day three the average CO₂ level consequently raised and reached almost equivalent to day one.

• Foliage plants again found to be more impressive in reducing the CO₂ level as compared to succulent plants in opened windows, closed windows and with fan in ON situation. While succulent plants were great in reducing the CO₂ level with fan OFF condition. The best results were found by keeping four succulent plants in drawing room with opened windows which reduced the CO₂ level up to 70.5 ppm.

• Houseplants helped certainly in depreciating the indoor carbon dioxide levels in both the areas of the sample residences selected for the purpose of the study.
• The significant difference was found in majority of the values of ANOVA, Paired-t and Standard Deviations, under all the selected subparameters except few, but it proves the effectiveness of houseplants in improving the IAQ with special reference to reduce the CO₂ concentration in the indoor air.

Impact of Houseplants on SO₂ Level in Residential Buildings

                  In the selected residences, while conducting the experiments the presence of SO₂ was found to be ‘zero’. Hence, the impact of houseplants on this parameter of air quality could not be assessed.

Impact of Houseplants on NO₂ Level in Residential Buildings

At the time of conducting the experiments in the sample residences selected for the purpose of the study, the presence of NO₂ was already in a ‘weak position’ and found to be ‘nil’. Hence, the parameter could not be judged.

Impact of Houseplants on VOCs Level in Residential Buildings

While conducting the experiments in the residences selected as sample for the research purpose, the presence of VOCs was already ‘feeble’ and found to be ‘zilch’. The research could not assess the impact of houseplants on this parameter.

• Other Characteristics of Air

Impact of Houseplants on Sound Level in Residential Buildings

• Sound waves in the air were more accousted by the succulent plants as compared to foliage plants.
• The increment in houseplants certainly helped in absorbing greater decibles of noise.
• The sound level decreased after keeping one, two or four foliage/ succulent plants on day two and again sound level went up on day three after the removal of houseplant/s.

• Succulent plants again found to be more impressive in reducing the sound level as compared to foliage plants in opened windows, closed windows and with fan in ON situation. While foliage plants were great in reducing the sound level with fan in OFF condition. The results were found by keeping four succulent plants in dining / living room with opened windows which reduced the sound level up to 7.86 dB.

• Houseplants were able to reduce the sound level in both the areas of sample residences, selected for the purpose of the study.

• There was significant difference in majority of the values of ANOVA, Paired-t and Standard Deviations, under all the selected subparameters, thus it proves the effectiveness of houseplants in improving the IAQ with special reference to reduction in noise level indoors.

Impact of Houseplants on Presence of Smell/ Odour in Residential Buildings

Unwanted smell/ odour was absent in the selected residences, while carrying out the experiments. Hence, the researcher could not judge the impact of houseplants on absorbing the unwanted odour indoors.