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Indoor Air Quality In The Hotel Industry
by Barry Abramson, P.E.
While attention to IAQ has intensified in office buildings and schools, hotels
have been preoccupied with a construction and remodeling boom with little consideration
for IAQ. This may be changing.
Hotels present many IAQ challenges: from dealing with the disparate needs
of living quarters, ballrooms, food preparation, laundry facilities, and indoor
pools, to the difficulty of accommodating both smokers and non-smokers.
The smoking issue has received a fair amount of attention in the industry,
due to high profile battles over legislative attempts to ban smoking in hospitality
facilities. Philip Morris's counterattack campaign against smoking bans has
permeated the HVAC industry with its "Options" approach of emphasizing dilution
ventilation, filtration and directional airflow to deal with the effects of
environmental tobacco smoke.
Several articles in the Wall Street Journal covering IAQ in hotels have focused
on the subtler but insidious comfort and health threats: bacteria, mold and
mildew, odors and VOCs. The angle is that hotel guests routinely are subjected
to unhealthy indoor air, and the hotel industry is not addressing the problem.
A major article in the Travel section last summer reported that the hotel industry
spent more than $3 billion last year on renovations, while paying little attention
to modernizing or upgrading HVAC systems. The article points to a problem not
unique to hotels: capital investment focused on finishes and fixtures; neglect
for back-of-house infrastructure improvements.
A hotel can easily spend $3,000 to $6,000 to renovate a single guestroom,
without touching the HVAC system. Rarely are IAQ problems dealt with before
they become catastrophic. The American Hotel and Motel Association reported
several years ago that problems from mold and mildew alone required hundreds
of millions of dollars annually in remediation and repair costs.
The Wall Street Journal reporters stayed in nine hotels, set out petri dishes
in their rooms during each stay, and then sent the petri dishes to a lab to
do bacteria and mold counts. The reported results showed that the counts varied
widely between the hotels and pointed to potentially health-threatening levels
in some of the hotels. Of course, the results are highly suspect from a scientific
perspective due to the questionable sampling method, lack of identification
of types of microorganisms counted, and failure to test the outdoor ambient
microbial level for comparison.
One indisputable fact, though ? coverage of this issue in the Wall Street Journal
is both an indication of and contributor to growing concern about IAQ on the
part of hotel guests. And, if there is one problem that attracts attention from
hotel ownership and management, it's guest dissatisfaction.
For HVAC professionals in the hospitality industry, now is the time to champion
best practices for IAQ in both new building design as well as renovation of
existing facilities. Attention should be focused on the four key elements of
ventilation, filtration, pressurization and maintenance.
Determining the correct outdoor air ventilation rates for hotels has not been
the most difficult task. Although debate and controversy continue around various
other aspects of ASHRAE Standard 62, the recommendations for hotel ventilation
have changed little over the last 30 years. For some occupancy areas, recommended
outside air quantities have gone up slightly, while others have been reduced.
Using guest bathrooms as an example: the 1873 standard recommended 30 to 50
cfm (14 to 24 L/s) of exhaust per room. In 1981, it became 50 cfm (29 L/s),
and the 1989 through present standards have settled on 35 cfm (17 L/s).
While outdoor air quantity has not been a principal causative factor in hotel
IAQ problems, outdoor air quality definitely has been. Finding a good location
for outdoor air intakes can be difficult for any facility, but hotels pose unique
challenges. There are many obstacles to avoid: restaurant exhausts, laundry
exhausts, parking garage and loading dock fumes, and, of course, cooling towers.
It is surprising how many IAQ problems can be traced to contaminants entering
through poorly located intakes.
Sometimes the original design is okay until a major renovation i.e., when a
new restaurant exhaust is inadvertently located adjacent to the outdoor air
intake. Filtration often is a solution for poor outdoor air quality. The degree
and type of filtration can be selected based on the severity of the situation.
The introduction of unconditioned outdoor air is also a major problem, particularly
in hot and humid climates. HVAC systems can introduce outdoor air into a building
in two ways: intentionally and unintentionally. As far as the intentional introduction
of outdoor air through the ventilation system, the designer can pre-condition
the outdoor air to avoid the multitude of problems caused by moisture and condensation
in hot and humid climates. There is little excuse for an HVAC system design
that does not pre-condition outside air, given the availability of proven, economically
attractive and energy efficient means of pre-conditioning, and the dire consequences
of not doing so.
Designing to prevent the problems associated with unintentional introduction
of outdoor air via infiltration is a more difficult assignment. A major study
of problem buildings in Florida concluded that, "Given the present state of
the practice, whether a building will avoid serious, even catastrophic problems
due to uncontrolled airflow (which introduces outside moisture), is primarily
a matter of luck."
It has been suggested that to build hotels in hot and humid climates without
mold and mildew problems, mechanical design engineers must understand in great
detail how building envelopes and interior wall finishes function, and architects
must understand the role of HVAC systems in moisture control. This may be too
much to request. If we can at least focus the mechanical design on thoroughly
addressing pressurization issues, there is a hope for success.
It is commonly recognized that buildings, in general, should be slightly pressurized
versus the outdoors. Infiltration of unconditioned and unfiltered outdoor air
is never desirable. In a hot and humid climate, it is even less desirable, due
to the moisture content of the outdoor air, the propensity for high indoor humidity
conditions, condensation on interior surfaces, and the resultant microbial growth.
Hotels in hot and humid climates exacerbate these factors with internally generated
moisture from guestroom showers and housekeeping procedures. Add the complexity
of various potential HVAC system operating modes with changing supply and exhaust
airflows, and the task of maintaining positive pressurization can become quite
daunting.
Using guestrooms as an example: the bathrooms must be negative to the bedroom
areas, the bedrooms must be negative to the common hallway, and every area,
including wall cavities, chases and ceiling spaces, must be positive to the
outdoors. At various times, depending on system design and control, the bathroom
exhausts could be on or off, and the guestroom HVAC units could be on or off.
A hotel facilities management textbook concludes, after a brief discussion of
guestroom pressurization issues like these, "Coping with these types of problems
can be a real headache for management and staff."
The impact of improper pressurization isn't limited to moisture-related problems
in hot and humid climates. Pressurization determines the pollutant pathways
inside the hotel as well. Proper pressurization is one of three methods for
dealing with indoor pollutants, along with dilution and filtration. Sources
of undesirable air are everywhere in hotels: kitchens, laundries, indoor pools,
health spas, anywhere smoking is permitted, etc. again, proper pressurization
must be maintained under varying conditions, with building areas occupied or
unoccupied and individual HVAC systems on or off.
Many of the IAQ problems hotels experience can be prevented during initial
construction or major renovation with sound engineering design, quality construction
and thorough commissioning. However, a hotel's life cycle does not end at this
point. To ensure good IAQ past the transition from startup to ongoing operation,
effective maintenance is required. Every well-intentioned HVAC design element
can be superseded, every ventilation system component can be defeated, every
perfectly configured pressurization relationship can be destroyed, with a good
dose of improper maintenance.
As HVAC professionals, we should not breathe easy just because we've created
an elegant design, or even contributed to a successful commissioning process.
We must communicate to hotel owners and operators that effective maintenance
and well-trained building personnel are essential for sustaining healthy indoor
environments.
Reprinted courtesy of ASHRAE IAQ Applications,
© 2000
American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.
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