ASHRAE Journal - August 2021 - 67

COLUMN SUSTAINABILITY
ventilation systems to give equivalent ventilation performance
as one might achieve with mechanical systems.
This remains the challenge we attempt to tackle over a
century later in this design guide.
Ventilation is the provision of outside air to a space.
When people talk about natural ventilation in normal
parlance, they usually envisage opening a window to
bring fresh air into a space. The adjective " natural " is
used to differentiate the driving force causing the air
movement as compared to a " mechanical " means.
Most people will open a window to relieve staleness
of air or to cool a room down. For the purposes of this
guide, the former is considered " natural ventilation, "
and the latter is called " natural conditioning, " according
to the defi nitions established by ASHRAE. If a team is
successful at providing natural conditioning, it is highly
likely that natural ventilation is also accomplished.
Perceived Benefi ts and Risks
Natural ventilation or natural conditioning is often
proposed as an alternative to conventional HVAC systems.
There are many concerns that must be considered
when applying natural ventilation to commercial and
institutional buildings. Persuasive arguments are made
that appropriate relaxation of comfort standards for the
individual results in energy savings that, if applied at
scale, could contribute to climate change mitigation.
While social consciousness and reputational benefi ts
may be a factor in the decision to pursue natural ventilation,
clients will typically need evidence specifi c to the
scale of their own projects to make a credible argument
for a tangible benefi t before invoking that support. They
deserve to understand the benefi ts and risks of natural
ventilation as an asset-embedded investment, so that they
can judge its effi cacy against other priorities for funding.
One of the issues with jumping to the energy vs. comfort
argument directly is it typically does not match
benefi t and risk to the same stakeholder. There are arguments
within the defi nition of comfort itself that must
be resolved prior to addressing energy concerns. When
the issues are adjusted to match scale and target audience,
three classic dilemmas typically frame the start of
the conversations:
* Indoor conditions: environmental quality vs. comfort
(Figure 1);
* Occupant discretion: device control vs. situational
constraint; and
A U G U S T 2 0 2 1 ashrae.org ASHRAE JOURNAL
67
What's in the Design Guide
The recently released ASHRAE Design Guide for Natural
Ventilation provides a comprehensive overview of
the issues associated with
the application of natural
ventilation in modern buildings,
including:
* Perceived benefi ts and
risks;
* Relevant standards and
codes;
* Prescriptive compliance
paths to meet standards and
requirements;
* Characteristics of building envelopes and how
they affect natural ventilation systems;
* Terminology and key concepts;
* A deep feasibility analysis with a multi-factor assessment
of outdoor conditions; and
* Control of openings, including the use of motorized
openings.
Learn more about the design guide at www.ashrae.
org/bookstore
FIGURE 1 Balancing indoor conditions: environmental quality vs. comfort.
Environmental
Quality
Reduced Absenteeism
From Sick Building
Syndrome
Quiet Environment
Without HVAC Noise
Reduced Indoor
CO2 Levels
Increased Air Speed
and Ventilation Rates
Comfort
Increased Exposure to
Allergens and Particulates
Increased Noise Break-In
From Outdoors,
Less Speech Privacy
Reduced Comfort From High
Temperature and Yearlong
Temperature Variability
Variability of Air Movement,
Indoor Air Temperature
And Relative Humidity
http://www.ashrae.org/bookstore http://www.ashrae.org/bookstore http://www.ashrae.org
ASHRAE Journal - August 2021

Table of Contents for the Digital Edition of ASHRAE Journal - August 2021
