Comfort Considerations in Net ZEBs: Theory and Design - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 138

has become even more critical because strategies to reduce energy use and
improve indoor air quality often directly contradict good acoustic comfort
design practices:
- Natural ventilation improves both real and perceived thermal
comfort, provides fresh air to supplement or temporarily eliminate the
need for mechanical ventilation, and in many climates can completely
eliminate the need for mechanical cooling. However, open windows
often introduce outdoor noise into the workplace, which is a particular
concern in urban areas or beside busy streets (Ghiaus et al. , 2006).
Furthermore, good cross-ventilation requires an open concept design.
However, a lack of partitions between spaces (e.g., cubicles instead of
floor-to-ceiling walls) results in higher levels of sound transmission.
Thus, distracting conversations and other noises can cause poor
occupant concentration and comprehension.
- Deep daylight penetration in a space requires an open concept design,
similarly to natural ventilation. Closed offices and other small perimeter
spaces, if enclosed, prevent daylight from being able to penetrate to its
full potential (about 1.5 to 2.5 times window height for standard
windows (Reinhart, 2005) and five to six times window height if
advanced reflective systems are in place (Guglielmetti, Pless, and
Torcellini, 2010)).
- Exposed thermal mass (e.g., concrete structures) facilitates greater
ability to absorb solar gains and regular air temperatures - an
important element of low-energy passive buildings. However, hard
smooth surfaces are also poor sound absorbers and can lead to poor
acoustic comfort if such surfaces dominate a space.
The strategies to mitigate poor acoustic quality (the so-called ABCs of
acoustic design) include absorbing, blocking, and covering noise. Absorbing
meanstheuseofstrategicallyplacedsurfaces(e.g.,acousticceilingtiles,wall
panels, carpeting, furniture, and/or sound-absorbing artwork) to reduce
sound reflectance in a space. Blocking requires that the source of sound be
isolated (e.g., servers or photocopiers in a separate room). Covering means
masking sounds with white noise generators such that individual sounds
(e.g., occupant chatter) are indistinguishable. For instance, the NREL RSF
(see Chapter 7 for details) uses white noise generators to cover
conversations and other sounds. While mechanical ventilation often plays
this role, RSF does not use forced-air for heating and cooling, so ventilation