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
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.