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WAYS TO
AVOID HAVING A SICK BUILDING
As a result, these types of buildings have come to be known as "sick buildings". Investigations, of the reasons why people using these buildings become ill, center on the fact that these buildings have been found to foster mold, viruses and bacteria.
When building-related illnesses have been found to occur, the mold experts and trial lawyers move in and multimillion-dollar judgments often result. (4)
Five actions can be taken to avoid some of the sick building issues facing today’s professional architects and building owners. Properly implemented, these steps will most likely eliminate the cause of this problem.
These actions are as follows:
1. Prevent moisture from entering the building.
2. Control the humidity level in the building and in air conditioning ducts.
3. Avoid hazardous construction materials.
4. Control the sources of material that promote mold, virus and bacteria growth.
5. Provide proper maintenance procedures for building owners and managers.
Causes of Moisture in a Building
Moisture is the number one breeding ground for mold, viruses and bacteria.
In a colder climate, it is desirable to keep the heat and moisture inside the building during the winter. To do this, the building is insulated and a moisture barrier is placed on the inside of the building.
In a warmer climate, it is important to keep the hot humid air outside of the building. A properly placed moisture barrier can help. This moisture barrier needs to be placed at or near the outside of the building. This exterior moisture barrier provides a healthier environment in the building while reducing the operating cost.
Recent American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) studies advise avoiding a ventilated attic or a ventilated crawl space. However if these spaces are ventilated then a vapor barrier must be placed in the attic or crawl space.
A brick or porous wall requires an air space, a vapor
barrier, and a method to drain any moisture that might accumulate at the
vapor barrier. Synthetic stucco exterior walls are of particular concern
and call for a moisture barrier on the exterior surface or an air space
and a vapor barrier to avoid moisture related problems.
Humidity Level
In order to control the humidity level in a building,
the mechanical design team
must understand the intended use and what the building owner expects when
the building is occupied.
A 40 to 60%
humidity level is considered optimum. At this humidity level, the growth
of mold, bacteria and viruses is minimized. (5)
Today, many consulting engineers apply an energy efficient controllable thermosyphon run around heat pipe exchanger as an ideal and reliable way to provide conditioned air during the cooling season. This addition to a typical air handler often reduces the relative humidity of the air supplied to duct to 70% or less while providing the air conditioning system with the capability of maintaining a 40 to 60% relative humidity level in the building without adding additional heat load. Over the life of the building, this approach, while more expensive up front, has proven to be a very attractive low operating cost technique of properly controlling relative humidity levels.
As energy costs escalate,
this energy efficient humidity control technique will become more commonplace.
The use of a controllable thermosyphon run around heat pipe also provides
the Heating, Ventilating and Air Conditioning (HVAC) design engineer with
the ability to meet a key requirement by specifying an air conditioning
system that has excellent moisture removal at both part-load applications
(that is, applications that are lower than peak load) as well as at peak
load conditions.
Should an engineer design for peak load and ignore the part-load applications, an oversized, inefficient system may result with poor moisture removal at part load. For example, at a 50% part load condition most air conditioning systems on the market today have very limited, if any, moisture removal capability. Because it is necessary to have moisture removal at part-load applications, the controllable thermosyphon heat pipe is an ideal means for the air conditioning system to maintain the necessary level of moisture removal at part-load applications.
In addition to considering the need for good moisture removal for part load conditions, the prudent design engineer should insure that the conditioned spaces have positive pressure during hot and humid conditions. Positive pressure is also necessary during other seasons when minimum ventilation is needed.
Too low a moisture level can occur in buildings located in regions where the winter design temperature is below 20º F. In these cases the latent load may not be sufficient to maintain a minimum level of 40% humidity. In this situation it may be necessary to add some moisture to attain the targeted relative humidity range of 40 - 60 %.
Hazardous Construction Materials
While hazardous construction materials should be obvious to everyone,
it is sometimes hard to anticipate the side effects when specifying building
materials. Just as there are side effects in the medical industry from
treatments or drugs, there are serious side effects that can result from
the construction materials used in modern building.
Common hazardous materials to be avoided are:
Any type of paint
that contains lead; asbestos that may be contained in floor tiles, roofing
felt and insulation material; formaldehyde in particleboard; certain glues;
ketones that generate unhealthy paint fumes; and inflammable materials.
The off-gassing of carpets and particleboard is an example of how components
can reduce the indoor air quality in a building. Additionally, any materials
that are toxic, carcinogenic, or will cause an allergic reaction, a rash,
or asthma, are all examples of hazardous materials that should be avoided.
Carpet, textiles and other materials often are specified to optimize the
esthetic impact of a building. These materials can, at times, provide
a source of food for molds, viruses and bacteria. When buildings are designed
for the sick, the elderly, restaurants or schools, carpets and textiles
should be limited for these same reasons.
The use of solvents can be a problem due to toxic fumes. Often the use of oil-based paints can be avoided. One preventative measure available is to require prior approval before use of such materials.
Building Maintenance Procedures
A poorly maintained building will often be dirty and serve as a host environment for mold, viruses and bacteria. The air conditioning system, without proper maintenance, often will not be operating efficiently and may not remove moisture from in a building. Upon examination we often find that the building has humidity levels that are excessive.
Moisture Code Requirements
The code requirements for moisture-resistant construction vary. This is
an expanding and developing part of the construction industry. The Southern
Standard Building Code Congress does require an exterior vapor barrier.
There is also a section in the Fundamental Handbook of the American Society
of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) that
addresses this subject. ASHRAE discusses it in their Chapter on Thermal
Insulation and Vapor Retarders for air conditioning buildings in humid
climates.
ASHRAE/ANSI Standard 62-2001 “Ventilation for Acceptable Indoor
Air Quality”, Paragraph 5.10 and 5.11, promotes maintaining a building
relative humidity within the 40 to 60% range and states, “If the
relative humidity in occupied spaces and low velocity ducts and plenums
exceeds 70%, fungal contamination (for example, mold, mildew, etc) can
occur.”
These code requirements are usually considered to be the minimum construction
standard acceptable. In the current atmosphere of developing code requirements,
exceeding the minimum code requirements seems logical when striving to
provide a quality building.
Existing Buildings
With existing buildings, the building owners and operators of today are well advised to consider placing their emphasis on these same key elements.
Moisture barriers may need to be reviewed to insure that they were correctly placed and properly installed for the buildings’ climate location.
Mechanical equipment in many cases needs to be modified to improve its moisture removal capacity. This is especially important if a sensible heat ratio has been changed due to load reductions such as the addition of better insulation or windows or lighting improvements. Such energy savings tend to unbalance the original building cooling design load so that the moisture portion is increased beyond the air conditioning systems capacity. Often it is possible to improve the moisture removal of the mechanical system while improving the building’s energy efficiency
Periodic inspection
and evaluation of a building as a healthy environment must continue over
the life of the building.
Conclusion
Follow these simple actions to avoid having a sick building:
• Prevent moisture from entering the building
• Control the humidity level in the building and its air conditioning ducts
• Avoid the use of hazardous construction materials
• Control the sources of material that promote mold, virus and bacteria growth
• Provide proper maintenance procedures to building owners and managers
In the final analysis, it is the responsibility of everyone: the building owners, their property managers, and the occupants themselves to maintain or insure the building is a clean and healthy environment. The final result is worth the investment by extending the useful life of the facility while avoiding the risk of having a sick building and the potential associated litigation.
References:
1. “Is your
office killing you?” BusinessWeek June 5, 2000
2. “Mold: a fungus among us” Realtor magazine December 2001
3. “Mold in Schools: a health alert” USAWEEKEND August 18-20
2000
4. Polk county court house settlement totaled 27 million dollars, while
EPA headquarters in Washington DC lawsuit was for 35 million dollars
5. Arundel, A.V., et al, “Indirect Health Effects of Relative Humidity
in Indoor Environments”, Environmental Health Perspectives, Vol.
65, pp 351-361, 1986
6. Mr. Somchai Paarporn, P.E., ASHRAE Journal, June 1999; pages 32-38-
Runaround Loop Heat Recovery with Dehumidification System
7. “Heat Pipes, Your Answer to Cooling and Humidity Problems”,
Edison Electric Institute, Washington, D.C. (07-26-91)
8. “Moisture Control in Buildings”, Chapter 23.4–23.15,
ASHRAE Handbook Fundamentals
9. ANSI/ASHRAE Standard 62-2001: paragraphs 5.10 and 5.11
About the Authors:
Mr. Louis N. Drake III was a practicing professional engineer in the air conditioning field since graduating from Georgia Tech. He died in 2004. His professional career included employment as a Naval Officer, Sales Engineer for an air conditioning equipment manufacturer and a Design Engineer at the Charleston Navy yard. He was a founding member of the Charleston Chapter of the American Society of Heating Refrigeration and Air Conditioning (ASHRAE). During the period 1980-1995 he was employed as a Staff Engineer and Project Manager at the Veterans Administration (VA) Medical Center, Charleston, S.C. During the period 1996-2003 he served as Vice President of Engineering at Carolina Heat Pipe, Inc. and was responsible for many successful applications.
Mr. Richard W. Trent is a graduate engineer who majored in Heat Engineering at SUNY Maritime College and completed graduate refrigeration work at Columbia University (NY). His employment career includes: Chief Engineer of Naval and Merchant Vessels; Manufacturing Engineer and Manufacturing Program Manager for Carrier Air Conditioning Company; and ASHRAE Society Regional Vice Chairman. He is President of Carolina Heat Pipe Inc and holds several U.S. Patents for the Application of Heat Pipe Science to Heating, Refrigeration and Air Conditioning Systems.
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Copyright 2004 Carolina Heat Pipe, Inc.
109 Wappoo Creek Drive, Suite 4B; Charleston, SC 29412
www.carolinaheatpipe.com