Since the 1970s, architects, city planners, and engineers have been thinking about green or sustainable buildings, frequently in response to rising energy costs. Although the focus of green buildings is on how structures can be made in ways that are environmentally friendly and resource efficient, there has been an increase in interest in recent years on understanding and enhancing internal environments as well. The emphasis has switched from green to healthy buildings as a result. In order to improve the indoor environments where people spend the majority of their waking hours, healthy buildings incorporate ideas and insights from the domains of engineering, construction, medical, and psychology.

Measures to make a Healthy Building
Researchers from the Harvard T.H. Chan School of Public Health have highlighted some key areas to focus on in order to improve indoor quality and thereby make a building healthy:
1) Ventilation: Bringing fresh air from the outside into the building, typically through HVAC systems.
2) Air quality: The presence and abundance of harmful agents, including particulate matter, volatile organic compounds (VOC), and carbon dioxide (CO2).
3) Thermal health: The combination of thermal conditions that affect the occupants’ sense of comfort, mainly temperature and relative humidity.
4) Dust and pests: Dust accumulates in office environments as people are constantly entering them from the outdoors, and pests such as dust mites can often carry unwanted allergens.
Impact of IEQ on health and productivity
Changes in cognitive function and quality of life can be influenced by a healthy building with a good IEQ (indoor environment quality). Researchers have concluded that there is a strong business case that can be made for healthy buildings as -
a) A healthy building has a positive impact on health, quality of life, focus, and productivity;
b) Such a building will attract and keep better and productive employees;
c) Any business' overall prosperity is advanced by enhancing the quality of a facility which results in improvement of the health and lives of employees;
d) Employers gain from a higher employee retention rate while employees are content since they can work effectively and in excellent health.

This research, which was published in Environmental Health Perspectives, compared the emissions of volatile organic compounds (VOCs) from conventional buildings, green buildings with lower VOC levels, and enhanced green buildings with lower VOC and lower carbon dioxide levels, simulating additional ventilation.
A second study by the similar group of researchers suggests that certified green, high-performing buildings also help residents sleep better. All around the world, the business case for healthy buildings is expanding.
Recently, there has been an increase in demand for certified healthy buildings, as evidenced by global capital flows and rental rates. Rental premiums of 4.4 to 7.0 percent over comparable standard buildings were specifically received by certified healthy structures.
Humans spend up to 90% of their time in indoor environments. In the era of digital technology and 'work from home' culture, we are increasingly becoming an ‘indoor species’. Therefore, we must not undervalue, instead understand and emphasize the impact of these environments on our health and productivity.
What should be the future?
All old and new buildings must have engineering upgrades to increase fresh air circulation via high-performance ventilation systems. Appropriate policy action will ensure that the benefits of a healthy building are enjoyed by all. In light of the Covid-19 pandemic and the future pandemics to come, we must not forget to emphasize on designing structures that have good indoor quality and help us live a healthy life.