The built environment has a profound impact on our health and happiness. Clean air and clean water are basic necessities for survival. Increased urbanisation, vehicular emission and several other human-led activities have led to deteriorating air quality, particularly in urban areas. And the quality of outdoor air has a deep correlation to quality to indoor air in all spaces, whether they are naturally ventilated or mechanically conditioned and ventilated. In addition, interior fit-outs also add to pollutant levels in a space; at times, indoor levels of pollution may actually be five to six times higher than outdoors.
Research has proven that employees in spaces with high levels of circulating outdoor air and low levels of volatile organic compounds (VOCs) performed 101 per cent better on cognitive tests than workers in conventional workplace settings. In fact, the increase in cognition can generate as much as $6,500 in improved productivity per person per year, according to a study by Harvard University.
What is 'good'or 'bad' IAQ?
Many a times, we walk into an office and it may smell of dampness or mould, the air may be dusty, have strong smelling volatile organic compounds and we may feel fatigued or tired in a space even after occupying it for a short duration of time. All these are possible signs of poor indoor air quality (IAQ). These conditions get aggravated by poor outdoor air as we rely on outdoor air for fresh air intake for any space. The controllability of IAQ is easier in a conditioned and mechanically ventilated space than in a naturally ventilated space. Thus, there is an inherent conflict between energy consumption and IAQ in areas with high pollution loads. My experience in walking the corridors of many offices to evaluate their efficiency has revealed that the outdoor air system is often shut down to reduce energy costs.
No one is able to realise the impact, as we usually do not measure IAQ parameters. But studies have shown that the bad air has a far-reaching negative impact on health. The main components of outdoor air pollutants are dust, fine and ultrafine particles, and gases such as NOx, SO2, ozone and carbon monoxide, while the main components of indoor pollutants are VOCs from furniture, finishes and fit-outs, rising CO2 levels from occupants, mould, cleaning agents and tobacco smoke, among others.
Outdoor pollution control requires city-level intervention and policy interventions that have a long-term positive impact on the health and well-being of citizens. These also reduce the stringency of interventions required to be taken at the building level. Take the example of this building in Milan, which has adopted extensive vertical gardens to filter out air, add greenery and reduce heat-island impact. It requires rigour in design, execution and maintenance for such structures.
Indeed, IAQ management requires multipronged strategies that start with source control, addressing sources of contamination, customised ventilation and filtration and, most important, appropriate maintenance and operation of the system. Take another example of the Paharpur Business Centre (PBC) in New Delhi. Located in an area with high levels of outdoor air pollution, PBC boasts good air quality, thanks to the extensive air-filtration strategies deployed and the use of plants for air-quality enhancement. This LEED Platinum-certified building has a hybrid air-filtration system that includes mechanical equipment and air-filtration plants, grown in hydroponics. The building has a pre-treatment air plant and is kept at a positive pressure to avoid ingress of outside polluted air.
This unit consists of various components, including a heat exchanger, to pre-cool the air without adding humidity. The air further passes through Microvee and HEPA filters. An electrostatic filter is used to remove particles from the air with highly charged electrodes that ionise the air. In an air-purification system, activated carbon filters are used in conjunction with HEPA filters to trap allergens and impurities like ozone, dust, lint, mould spores, smoke, benzene and other VOCs. This cooled air goes to the greenhouse, which has patented planters with special plants, grown in hydroponics to reduce bacteria and fungus, VOCs and CO2 in the air.
Steps to better IAQ
Outdoor air: Investigation of local outdoor air quality at the project location is necessary to determine if the project should adopt a mechanical, mixed-mode or natural ventilation strategy.
Cities such as Delhi with perpetual poor outdoor air quality require mechanical ventilation with extensive filtration to maintain healthy IAQ. The recommended value of PM10 beyond which use of outdoor air (in its natural state) should be cautionary is 50 micrograms per cu m.
What to filter and clean? Ascertaining sources of contamination is another critical aspect of good IAQ design. Building nearer traffic emission sources needs to be more cognizant of NOx, CO and ozone as possible pollutants in addition to particulate matter and VOCs. The particulate matter concentration and its fineness distribution are also the key to the choice of filtration systems. For example, the installation of high-efficiency filters such as MERV 13 in isolation may not be appropriate in regions with high levels of coarse particles. Multilevel filtration is necessary in such situations where pre-filtration is applied to remove coarse particles followed by high-efficiency filters. Activated carbon filters are also recommended to remove VOCs.
In buildings with air-conditioning, it is recommended to employ ultraviolet (UV) lamps (using a wavelength of 254 nm so as not to generate ozone) on the cooling coils and drain pans of the mechanical system supplies to prevent mould growth.
Design for positive pressure: Maintaining positive pressure in mechanically ventilated spaces can keep pollutants out. Negative pressure in a building allows infiltration through openings, crevices and joints. Outdoor air volume should be at least 10 per cent higher (or as recommended by the MEP consultant) than building total exhaust air volume to maintain the building in positive pressure.
Use of plants for better IAQ: Certain common indoor plants (areca palm, rubber plant, etc) provide a natural way of removing toxic agents such as benzene, formaldehyde and trichloroethylene from the air, helping to neutralise the effects of 'sick building' syndrome. However, it may be noted that indoor plants can hardly be beneficial for controlling particulate matter (PM 2.5 and 10) and filtration media is essential for removing particulates.
Follow standards and certification requirements
Globally, rating systems have been instrumental in moving the needle on several best practices, including designing for and maintaining good IAQ in buildings. Under LEED Building Design and Construction (BD+C), for example, projects can achieve up to eight Indoor Environmental Quality credits to meet air quality benchmarks. Credits are awarded for ventilation designs that bring in and monitor fresh outdoor air and filter particulates. Buildings can also earn credits or the use of low-emitting (low or no-VOC) materials, green cleaning products, and pest management that minimises exposure to pesticides. The WELL Building standard additionally lays out requirements for mould and microbe control, direct source ventilation, etc. Both these systems influence designers and builders to create energy-efficient workspaces with cleaner air and healthier, more productive occupants.
The Indian Society of Heating Air-Conditioning and Refrigeration Engineers has brought out a standard on good IAQ in Indian buildings. It provides the limits for contaminants and pollutants in good to acceptable range, and lays out methods to monitor, and evaluate IAQ in buildings in India.
Choose with care
Furniture and furnishings, paints, interior finishes, cleaning agents, copiers and printers are potential sources of indoor pollutants that need to be controlled. Materials with low VOCs and toxicity levels are preferred. The use of perfluorinated compounds, flame retardants, phthalate (plasticisers), isocyanate-based polyurethane and urea formaldehyde should be restricted during material selection for interiors.
Measures to maintain
Monitoring of particulate matter, CO2, ozone, SOx and NOx, if there are possible sources in indoor spaces, can provide insights to better management and control. In conclusion, maintaining good IAQ is of utmost importance in homes, offices and all the spaces we live and work in.
About the author:
Mili Majumdar, Managing Director, Green Business Certification Institute (GBCI), India, is responsible for technical adaptation and customisation of the portfolio of rating systems of GBCI for the Asia-Pacific region. She is also responsible for customer coordination, education, training, and developing market mechanisms for the adoption of tools and rating systems for the region.