Comfort Considerations in Net ZEBs: Theory and Design - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 140

occupants, equipment and HVAC distribution, or the outdoors (e.g., a point
source of pollution or from polluted urban environments).
Carbon dioxide is frequently cited as a major source of IAQ problems.
However, this is because carbon dioxide is a good indicator of IAQ in
occupied buildings and it is considered a surrogate . It correlates well with
occupancy since occupants are the primary source of CO 2 in most buildings
and can be used to approximate the outdoor air supply rate if the occupancy
and outdoor CO 2 concentration are known, as follows:
(3.28)
where (∞) is the steady state indoor carbon dioxide concentration, P is
the fraction of outdoor air in the air supply, Q is the air supply rate, is
the outdoor carbon dioxide concentration, S is the generation rate of carbon
dioxide, and V is the volume of the space. Many ventilation standards (e.g.,
ASHRAE Standard 62.1 (ASHRAE, 2010)) use a certain allowable carbon
dioxide concentration (e.g., 1000 ppm) to provide minimum ventilation
rates for different space types (e.g., classroom, office, kitchen).
The three main methods to ensure good IAQ are: (1) removal or reduction
of source of contaminants, (2) ventilation, or (3) filtration of contaminants.
The first approach, to attempt to eliminate the source of contaminants, is
thepreferredoptionbecauseitrequiresnomaintenanceoroperatingenergy
use. Use of low-VOC paints, furniture, and other finishes are also good
approaches to achieve this. Careful design of walls and HVAC systems to
minimize chronic moisture or sitting water is essential to minimize mold
growth and other bioaerosols. Ventilation and filtration cost energy:
electrical energy (fans and pumps) and thermal energy (for conditioning
supply air) for ventilation and electrical energy to run fans to overcome
pressure drops in filters. The thermal energy demands of ventilation can be
partly reduced using heat or energy recovery ventilation.
3.6 Conclusion
This chapter examined thermal, visual, and acoustic comfort, and indoor
air quality. These elements of indoor environmental quality are critical to
the success of Net ZEBs. While indoor conditions were traditionally viewed
as being passively endured by occupants, it is now widely accepted that