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– Why Do HVAC Systems Suck So Much?
SES Consulting Inc.
commercial buildings are dissatisfied
with their space temperature and indoor air quality. That statement may
not surprise most of us in the HVAC industry, but when you stop
to think, it is a rather shocking denunciation of our craft. This
dissatisfaction applies equally to both green and conventional
buildings. Providing ventilation and space temperature control are the
entire reason that HVAC systems exist, but the overwhelming majority of
end users aren’t happy with the systems that we’re designing and
In most normal businesses, this level of dissatisfaction
long ago triggered some market response to improve things.
However, in the HVAC industry, there is a great deal of separation
between the designers and builders and the ultimate end user which
makes that kind of market feedback very difficult. It’s not exactly
easy to buy a new HVAC system if you’re unhappy with the one you
Many would be quick to point out that despite occupants’ opinions, air
quality and space temperature in most buildings are within “acceptable”
bounds most of the time. I have certainly been guilty of this myself in
the past. This attitude might be appropriate if we see ourselves as
simply providing life support systems that meet the conditions of
maintaining human life (or whatever conditions happen to be in the
lease). On the other hand, if we care about making people
comfortable, then I think we have to admit that we’re falling well
short of achieving that.
Like many engineers, I sometimes struggle with empathizing with the needs of my fellow humans. It turns out that there is a very practical reason to care about whether or not people feel comfortable; people who are comfortable in their space are more productive, have lower absenteeism, less turnover, etc. These are all things with very tangible costs associated with them. To illustrate this, let’s consider a typical 100,000 sq ft commercial office building that we might expect to be around for 100 years. If we consider the rough numbers over that period (assuming constant $), then we get the following breakdown:
Considered another way, in just one year, the wages paid
to the people
in a building is equivalent to the construction cost of that building.
It’s clear that even small improvements that influence wage costs or
productivity will have an enormous economic impact, easily dwarfing
costs associated with operations and maintenance. Making occupants
happy is worth caring about.
So why are people so unhappy with their HVAC?
I think that a lot of it comes down to the simple fact that, as an
industry, most of us simply don’t understand what it is that people
want. Most HVAC practitioners, I believe, have a good grasp of the
physics of comfort, but a very poor understanding of the psychology of
comfort. An occupant will never tell you that they want it to be 73°F
with 800 ppm of CO2 and 4 air changes per hour. This is what the
sensors that operate our HVAC systems measure and forms the basis of
how we will try to address complaints about temperature or indoor air
What do people want? The answer, it seems, is that it depends on. Part of the problem is that what people want changes all the time, so having a system based on fixed set points is almost guaranteeing that you’re going to be making people unhappy. I would also submit that the average thermostat has a fairly terrible user interface, assuming of course that you’re lucky enough to have access to one. Add to this hot and cold complaints that disappear into the ether with little feedback as to what, if anything, was done in response. If you don’t feel up to complaining, then you might just sit there distracted by how uncomfortable you are. All things considered, in your average office building the occupant is in for a frustrating experience if they happen to be uncomfortable. No wonder satisfaction levels are so low.
However, in response to this situation we are starting
to see a
revolution in occupant centered design and control. The move towards
individual controls is being enabled in large part by the near
universal pervasiveness of the smartphone. This provides the ability
for people to be the sensors. Our connected devices can allow us to be
connected directly to the building automation system, which gives the
means for people to tell their building exactly what it is they want.
Smart vendors will see this not merely as an upgrade to the
old-fashioned thermostat, but rather as having the potential to
fundamentally change how occupants interact with their surroundings by
providing a two-way flow of information. Occupants will not only be
able to register their comfort preferences but will be given
information that will provide context that will help shape their
preferences. This might include things such as their past preferences,
the preferences of their zone mates, or even the energy impact of their
We can also think beyond the controls themselves and look at exactly
what is being controlled. For a long time, operable windows were
considered taboo under the premise that it made the HVAC system harder
to control. That thinking has now changed as the considerable benefits
from having occupants able to control their access to fresh air have
been appreciated. This is driven above all else by the fact that people
like to be able to open the windows. Operable windows are a
great example of where design orthodoxy based on optimizing the physics
of the HVAC system has given way to a more occupant centered approach
that considers the needs of the people first. By extending this concept
further, we might start to consider other ways that we can give
occupants greater control over their environment. Personal space
heaters come with serious safety issues, but equipping people with
heated office chairs might be a good idea. Similarly, mini USB
powered fans could be made standard issue equipment.
Right now, facility and energy managers alike tend to see the presence of things like space heaters and fans as either signs that the HVAC system is failing to do its job or energy pigs that work against energy efficiency goals. It may be time to turn this thinking on its head. What if we start by giving people the personalized heat sources and ventilation devices that they obviously like, and design the operation of our HVAC systems around that premise? Instead of the HVAC system trying (and often failing) to maintain a 3°F dead-band, we set it for 6°F with the expectation that occupants use their personalized controls or personalized devices to fine tune their comfort. There is evidence that this approach not only works for maintaining comfort but actually can reduce overall energy consumption while significantly reducing or eliminating hot and cold complaints. To top it all off, there have also been studies linking personalized controls to improved productivity and increased workplace satisfaction.
Think of the last time you were in a car or on an
airplane (I’m talking
about those little adjustable air nozzles above your head); you
probably took advantage of personalized climate control systems. Try to
imagine how much more unpleasant your experience would have been in
those cases without the ability to make adjustments or if you had to
ask the flight attendant every time you wanted a bit more air. You
would probably consider flying on a different airline next time,
especially if you had to spend 40 hours a week on that plane. For some
reason, this situation has become the norm in the majority of
workplaces. There is an enormous opportunity (not to mention an
extremely attractive business case) at hand, to listen to what
occupants want and focus on creating HVAC systems and user interfaces
for our buildings, that focus above all else on making people happy.
Please join us at AHR in Las Vegas as we continue the exploration of
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