ASHRAE Journal - August 2021 - 68

COLUMN SUSTAINABILITY
* Cost of ownership: market value vs. operational risk
(Figure 2).
The goal of the design team is to address the likelihood
and extent of risk and to demonstrate the benefits in the
application. Within each discussion, the client can test
his or her capability and tolerance level to manage the
risk against the attractiveness of the noted benefits. Each
comparison can be evaluated independently for viability.
Then, if not all priorities are shown to be reasonably
viable, the client can clearly see the choice at hand.
Weighing the Benefits and Risks
Once the client has agreed that indoor conditions
under a natural ventilation scheme would be acceptable
and that the target tenants would have enough personal
freedom to adjust devices and clothing and that the cost
of ownership is manageable, the conversation of comfort
versus energy use can be further explored in greater
detail.
The California Energy Commission funded a study2 to
determine the energy savings benefits of applying natural
ventilation in the state. Linden, Arens and Daish2 is
a comprehensive study of the " benefits and barriers to
retrofitting California commercial buildings with natural
or mixed mode ventilation for cooling. " (p. iv). The
study found that energy savings for retrofitting natural
ventilation in conjunction with aggressive conventional
energy savings (power and lighting energy use reduction,
ceiling fans, external shades, increased insulation
and supply air temperature reset) could reduce cooling
energy by 44% in pre-2008 buildings, but acknowledged
that only 25% of that is due to the natural ventilation
itself after the other measures are applied (p.9).
When examined by California climate zone, the
aggressive measures and natural ventilation packages
average about 5% to 6% return on investment for large
and medium offices but struggle to reach 4% for most
small offices (p. 99). Chen, Augenbroe and Song3 have
a similar simulation-based exercise across four U.S.
climate zones for small and medium offices, estimating
the potential for a 17% mean energy savings in Atlanta,
19.7% in Seattle, 43.8% in San Francisco and 42.9% in Los
Angeles.
While both of the above-listed studies normalize for
compliance with either the adaptive comfort or predicted
percentage dissatisfied-predicted mean vote (PPD-PMV)
comfort standard, Brager and Borgeson4 explicitly
68
ASHRAE JOURNAL ashrae.org A U G UST 2021
Market
Value
Improved Reputation for
Environmental Stewardship
Improved Resilience for
Operation During Extreme
Hot Day Events
Direct Access to Fresh Air
as Differentiating Feature
Decreased Annual Energy and
Equipment Maintenance Costs
Operational
Risk
Stability of Long-Term Value, in
Light of Climate Change
Unpredictability of Daily
Outdoor Conditions-First
Cost of Backup Systems
Tenants Misunderstanding
Building Operations
Increased Janitorial and
Security Operating Costs
FIGURE 2 Balancing cost of ownership: market value vs. operational risks.
provide a comparison using simulation of energy cost,
adaptive and PMV comfort for a well-performing mixed
mode building placed in a handful of California climate
zones to explore an annualized understanding of comfort
range exceedances as an important parallel factor when
evaluating the potential impact on buildings' energy
use. This study is unique in that it simulates and reports
comfort simultaneously to energy savings for each of the
studied climate zones. This direct comparative reporting
from simulation models can be applied at the single
building level to provide credible trade-off information
to help with decision making on the energy versus comfort
question after many of the other risks have already
been deemed manageable.
References
1. Boyle, R. 1899. Natural and Artificial Methods of Ventilation.
London: Robert Boyle & Son, Limited.
2. Linden, P., E. Arens, N. Daish. 2016. " Natural Ventilation
for Energy Savings in California Commercial Buildings. " CEC500-2016-039.
California Energy Commission. " https://tinyurl.
com/4shcsh8x
3. Chen, J., G. Augenbroe, G. X. Song. 2017. " Hybrid ventilation
potential investigation for small and medium office buildings
in different US climates under uncertainties. " 34th International
Symposium on Automation and Robotics in Construction (ISARC 2017)
894- 900. https://tinyurl.com/5fnhsujt
4. Brager, G., S. Borgeson. 2010. " Comfort Standards and
Variations in exceedance for mixed-mode buildings. " Building
Research & Information 39(2):118 - 133. https://tinyurl.com/y4w7ptjr
https://tinyurl.com/4shcsh8x https://tinyurl.com/4shcsh8x https://www.tinyurl.com/5fnhsujt https://www.tinyurl.com/y4w7ptjr http://www.ashrae.org
ASHRAE Journal - August 2021

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