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Trade-offs between energy efficiency and indoor air quality Wenfa Ng 24 Mar 2017.pdf (149.6 kB)

Trade-offs between energy efficiency and indoor air quality

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journal contribution
posted on 2017-03-24, 01:06 authored by Wenfa NgWenfa Ng
Recognition of increasing surface air temperatures and climate change has altered governments and public's perception of environmental protection, fossil fuel use and energy efficiency. Specifically, there is increasing awareness that it is possible to contribute, in a substantial way, to reducing energy use and protecting the environment against climate change. One visible example of this is the promulgation of the "green building" concept around the world, where new buildings are designed with efficiency in water and energy use in mind. Concomitant with this is the drive towards increasing energy efficiency in public and private buildings through a combination of education and incentive programs. Efficiency in energy use in buildings is usually gained through: (i) maintaining a higher indoor air temperature of 25 oC, (ii) increasing the air recirculation ratio, and (iii) reducing energy loss through improving building insulation in windows. But, what is the effect of an energy efficiency drive on indoor air quality? Specifically, while increasing the amount of air recirculated helps reduce cooling cost for fresh air drawn from hotter air outside, a greater proportion of recirculated air also increases the residence times of volatile organic compounds (VOCs) released from various furniture and upholstery; thereby, degrading indoor air quality, which may negatively impact on occupants' productivity. Similarly, many post-modern buildings have full glass facade where there are little or no gaps between the glass and building structure; thus, such buildings are not "breathable" as contaminants such as dust and VOCs accumulate in the building, contributing to the "sick building syndrome". Hence, there exists a distinct trade-off in our march towards increasing energy efficiency in buildings and maintaining or improving indoor air quality, which impacts on overall productivity of building occupants as well as occupational safety and health. With lower proportion of fresh air intake in each recirculation of air, together with reduced exchange of indoor air with the building exterior, various contaminants such as dust, carbon dioxide, and VOCs accumulate, which collectively reduce the habitability of the indoor environment for work and leisure, which in extreme scenarios, could raise serious safety and health issues. Thus, a holistic and innovative approach is necessary as we tackle the challenges of implementing "green buildings" concept with protection of indoor air quality.

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