ASHRAE Journal - October 2013 - 10

letters

Comfort vs. Energy

engineer’s notebook

July’s column “Comfort vs. Energy Comfort vs. Energy Use
A
Use” exhibits the kind of thinking
that will prevent ASHRAE from
progressing the art of HVAC design
to deal with 21st century realities.
The author argues that somehow
aggressive energy-efficiency targets
are forcing engineers to use “innovative” new systems
that cannot be adequately modeled and as a result are
ending up with uncomfortable buildings.
As the column title implies, a trade-off exists between
comfort and energy efficiency. In my experience the
opposite is the case. The most energy-efficient buildings
are the most comfortable buildings. High performance
buildings are well-insulated, incorporate good lighting
design and shading, and have right-sized mechanical
systems controlled to respond to the actual loads of the
building. This eliminates wide temperature swings and
reduces air noise and drafts associated with oversized
equipment struggling to meet large building loads.
By Dan Int-Hout, Fellow ASHRAE

underfloor systems, resulting in the pulling, and rewriting, of
s a member of the ASHRAE Technical Activities Com- ASHRAE’s underfloor air distribution (UFAD) design guide
mittee (TAC), my assignment is to manage the new (which, sadly, is still lacking any real energy savings informaMultidisciplinary Task Group (MTG) committees. One tion). At the same time, many continue to push UFAD as an
of them is focused on energy targets, and they are working on “energy saving” strategy.
tweaking their scope.
In the meantime, practicing engineers are forced to “make
It appears that the term “energy target” has a specific meaning in stuff up” to calculate energy consumption for systems not
the energy industry that has nothing to do with energy conscious included in the available computer models. And, in the end,
design in buildings. The term seems to have been assigned to the buildings use more energy than predicted, and tenants fail to
practice of forcing electric utilities to use more renewable energy in renew the lease, looking for the fabled “comfortable space” in
their generation of electricity. This is an example of how the whole which to work.
issue of energy use and the prediction of energy consumption has
We use something on the order of $2/ft2·year ($22/m2·year) to
corrupted the goal of providing efficient and comfortable buildings. heat and cool a building, while salaries are more on the order of
Recently, the LEED Environmental Quality (EQ) committee $200/ft2·year ($2153/m2·year) (Figure 1). We can argue the numasked to see the weightings for occupant comfort vs. energy use. bers above, but not the orders of magnitude. Reducing energy
At first, the USGBC was reluctant to disclose them, but ended 30% is pennies compared to the cost of employing the folks who
up with equal weighting between energy and occupant issues. work in the environments we create. A net zero energy buildThose who force renewable energy, or energy conservation on ing, if actually possible, is still saving only 1% of salary costs!
building designers and architects, in place of the end goal—proMeasuring actual HVAC energy use is complicated, of course,
viding a safe and acceptable environment for the occupants of as is measuring occupant productivity. But as noted in articles
the buildings—are doing us no favors. It leads to complex energy recently published here, we do have productivity data, and it is
calculations based on no facts and only on wild assumptions that greatly affected by the environment we are tasked to provide.
in the long run, are proving to be unattainable.
In truth, we are, first of all, in the business of applied biophysThe result is that a number of LEED projects are not even ics. Doing so using the least amount of energy is not the goal,
coming close to the predicted energy savings. The same can but a part of the process. Sometimes we lose sight of that fact.
be said of a number of ENERGY STAR projects. Meanwhile,
BOMA reports that the number one reason for not renewing
Dan Int-Hout is a chief engineer at Krueger in Richardson,
the lease in high-rise buildings is occupant dissatisfaction with Texas. He is a member of SSPC 55, SPC 129 and consultant
the thermal environment (for at least the last 20 years in a row). to SSPC 62.1.
I would suggest that in addition to “targets” the goals should include some means
of validation of the calculated energy use.
People
(Salaries)
Maybe the word “realistic” needs to appear
Original
somewhere. And, it would be great if we
Original
Construction
Construction
Energy
could somehow get some data on the existMaintenance
ing mainstream computer models’ ability
to accurately predict the energy use of “innovative” systems, many of which cannot
Taxes
be modeled without the user making modiEnergy
Maintenance
Taxes
fications to existing software with no basis
for the assumptions necessary to make the
“innovative” systems work in the models.
A case in point is the General Services
Administration’s claim that it has 10 mil- Figure 1: (left) Life-cycle building costs breakdown; (right) life-cycle building costs
lion ft2 (929 030 m2) of non-performing breakdown with people (salaries).
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O ct O b e r 2 0 1 3

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Energy efficiency does not make buildings uncomfortable; but the lack of good mechanical engineering design
does. More is not better when it comes to HVAC design,
and ASHRAE needs to lead the way in promoting a new
perspective on what it takes to deliver comfortable,
energy-efficient buildings.
Jonathan Heller, P.E., Member ASHRAE, Seattle

July 2013

6/20/2013 2:55:11 PM

The Author Responds
While I fully agree that oversized equipment may lead to
occupant dissatisfaction as the system attempts to operate efficiently at part load (see my August column), there
are a large number of “energy-efficient” buildings where
occupant comfort has taken a back seat to energy savings.
I fully agree that “Energy efficiency does not make buildings uncomfortable; but the lack of good mechanical engineering design does.” Sadly, so does poor understanding of
how a building is supposed to operate. Innovative systems
need much more building operations training than more
traditional ones. Construction of innovative designs is also
often compromised by poor construction.

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ASHRAE Journal - October 2013

Table of Contents for the Digital Edition of ASHRAE Journal - October 2013