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Indoor air quality: Clean, green HVAC machine
24
Featurestory Cover
Filtration+Separation January/February 2007
Indoor air quality:
Clean, green HVAC machine S
o much depends on the air we breathe – our happiness, comfort and our health. Terry Townsend from ASHRAE says that not only does filtration play an important role in keeping air clean and creating a healthy indoor environment, but it also plays an important role in sustainable design.
Indoor air quality affects our quality of life – and our bank accounts – so it’s no wonder that building owners and occupants pay attention to the quality of air in our buildings, as a building’s air quality can have a huge impact on its occupants, especially in the workplace. It’s so important that several years ago, a World Health Organization working group concluded that “under the principle of the human right to health, everyone has the right to breathe healthy indoor air.”
related to the temperature, draft, humidity and odours in a building. Some of the most common building-related health complaints include eye, nose and throat irritation; upper respiratory symptoms; and skin irritations and rashes. Such symptoms together comprise what is commonly referred to as “sick building syndrome.” Improving indoor air quality can be a complicated task, given that so many
components are involved in its creation. As recognized in ANSI/ASHRAE Standards 62.1, Ventilation for Acceptable Indoor Air Quality, and 55, Thermal Environmental Conditions for Human Occupancy, IAQ depends on HVAC systems; properly selected, positioned and installed vapour retarders in building envelopes; pollutant source control; building occupants and
The good… So what is good indoor air quality? It’s difficult to precisely quantify but the environmental result is obvious. When a building has good IAQ, its occupants are able to work efficiently and comfortably in an environment that is comfortable and free of pollutants. A building is said to have good indoor air quality when it has no known contaminants at harmful concentrations and when 80 percent of occupants express satisfaction with the air. Sources of indoor air pollutants can include building materials, cleaning products, office equipment such as copy machines, HVAC equipment, and people themselves and the personal care products they use. Microbial growth, pathogens and mould can also contribute to a building’s ill effects when there is no proper ventilation in place.
…the bad… Bad indoor air quality’s effect on occupants isn’t superficial – it can cause many tangible symptoms. Discomfort complaints are commonly
fs4401_pg24_27.indd 24
Incoming outdoor air must be cleansed of pollutants in order to maintain a high indoor air quality at all times.
31/01/2007 09:17:02
Cover Feature story
Filtration+Separation January/February 2007
other building systems and components that provide routes of pollutant exposure and migrations. IAQ is even affected by the building’s site and access to sunlight, greenery and noise levels. In light of the given complexity, IAQ improvement will typically involve a combination of controls and measures involving several of these factors and will often include preventative control and remedial practices.
…and the remedy? Ideally, conversations about good indoor air quality would happen at all stages of a building’s life, from design to destruction, and would involve every party responsible for the building’s environment, including designers, builders, engineers, facility managers and building occupants. One good resource is the ASHRAE Guideline 0-2005, The Commissioning Process, which details the process for documentations and sets the foundation for communication about IAQ. However, even when such communication hasn’t taken place from a building’s foundation, there are still many remedial steps that building owners and operators can take to improve indoor air quality in the work place.
Source Control Pollutant source control measures are one of the most effective ways to improve indoor air quality. One easy way to begin is to isolate or consolidate contamination sources such as office equipment. By locating them all in one area, the contaminants can be more easily contained and ventilated. Other indoor air contaminants, such as outgassing, can be controlled simply by avoiding use of highemitting construction and furnishing materials such as particleboard and some carpeting and wall coverings. Although some products, such as carpet made from recycled tire products and insulation made from recycled cellulose, might be labelled as “green,” be aware that they can often have very high outgassing output and can be a large contributor to bad indoor air quality. • Be cognisant of occupant activities, and designate certain well-ventilated rooms for activities that may have a negative impact on indoor air quality. • Outdoor air can also act as a pollutant source, so use high-efficiency particulate and gas-phasing air cleaning. • Avoid cross-contamination from building exhaust into the building’s air intake.
HVAC System A building’s HVAC system is absolutely critical to its indoor air quality. After all, the purpose of an HVAC system is to provide for the occupants’ comfort and
fs4401_pg24_27.indd 25
health, which is the aim of good indoor air quality. An HVAC system must be properly designed, installed, commissioned, operated and maintained to produce maximum results and to prevent sick building syndrome from occurring. Ventilation is naturally a large part of an HVAC system and also of creating a healthy indoor environment. ASHRAE Standard 62 serves as the basis for almost all of the ventilation requirements contained in North American building codes. “While ventilation is not the only determinant of IAQ, occupants’ perception of air quality and health outcomes typically improve as ventilation rates increase,” says H.E. “Barney” Burroughs, a filtration expert and former ASHRAE president. At the very least, minimum ventilation rates as recommended in ASHRAE Standard 62.1 need to be maintained, but establish minimum ventilation rates based on the building’s needs and not by design occupancy, Burroughs recommends. • Consider the activities in the office to determine of rates above the minimums required by 62.1 need to be enacted. • Do not over-ventilate the office environment in the name of being “green.”
25
To ensure maximum efficiency, there should be continuous monitoring of the ventilation and humidity control systems as well as vigilant water and moisture control. HVAC system efficiency will also benefit from semiannual monitoring, testing, adjusting and rebalancing. Prior to any construction or remodelling, systems should also be flushed out, and construction should be isolated from buildings occupants by space, time or barriers to minimize infiltration of pollutants into the workspace. Remember that temperature control in offices is extremely important as well. If an office environment is either too hot or too cold, workers will be uncomfortable, and productivity will then suffer. ASHRAE recommends that office temperatures be set between 68-74°F in the winter and between 73-79°F in the summer to satisfy the majority of people in the workplace.
Keeping HVAC clean and green Air filtration first came to prominence in 1943 with creation of the HEPA. According to Burroughs, air filters’ original purpose was to protect HVAC systems’ heating elements from heat damage and flames caused by
• Monitor carbon dioxide levels and employ demand control to increase ventilation when needed and only for the actual occupancy of the building.
Operations and Maintenance Maintenance is extremely important to IAQ, and the lack of it can be quite costly. The costs associated with ill health and productivity loss can be far greater than the savings created from not performing needed maintenance. Instead of performing reactive maintenance, implementing a preventative maintenance system can greatly contribute to a building’s IAQ. Even in a building’s planning and design stages, building operators should consider the location of the HVAC system to allow for easy accessibility for cleaning and maintenance.
A company’s air filtration strategy must look at the needs of the staff as well as the technical possibilities.
31/01/2007 09:17:13
26
Featurestory Cover
Filtration+Separation January/February 2007
Test Methods for Gas-Phase Air Cleaning Equipment. Standard 52.2 establishes minimum efficiencies for filters and provides information on the performance of specific filters, allowing designers and operators to choose filters based on the contaminants found in a building. The standard also addresses the filter’s resistance to airflow. The standard uses mandatory language, which enables it to be referenced by other documents that are to be codified, such as Standard 62 and can be used to more accurately compare filtration products, predict their performance and select an air filter based on its efficiency for a specific situation. Other features include:
A selection of filter media used in indoor air applications.
the accumulation of lint, hair and other particulate matter. As air conditioning systems became more popular, the air filter took on the additional role of protecting cooling coils and the system in general to improve efficiency and increase equipment longevity while decreasing maintenance costs. Filtration and gaseous air cleaning within HVAC systems can strongly influence indoor pollutant levels. Anyone who has worked in an office during the ‘flu season’ knows the importance of filtration to keep virus and bacteria levels at a minimum and other tasks relating to IAQ. Filtration can be a local substitute of sorts for ventilation, as it allows local source control and enables contaminant control by occupants at lower cost than dilution because of the energy savings. Not only should incoming outdoor air be cleansed of pollutants, but exhausted air should be filtered as well to prevent cross contamination of air uptake. ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality, should be followe d at a minimum. Be sure to take the following steps in the workplace: • Use medium-efficiency particulate filters to protect heat exchange and distribution systems and to avoid feeding biological growth. This will also cut down on maintenance costs. • Use high-efficiency particulate filters to control disease-bearing organisms and inhalable particulate matter. • Use high-efficiency gaseous filters to control organic and inorganic compounds. In the best filtration plans, everything should be documented to help in analyzing trends and possible contaminant sources within the office.
fs4401_pg24_27.indd 26
Green buildings for clean air Filtration has a definite role in green building criteria. ASHRAE’s definition of a green building notes that a green building should have maximum indoor environmental quality, and filtration contributes to such. In rating systems such as the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED), credits are available for use of (at least) MERV 8 filters during construction and MERV 13 filters during normal operation. To simplify the general screening and selection process for users, the committee that wrote the standard derived a shortcut “handle” to communicate the general category of efficiency performance. This is the minimum efficiency reporting value (MERV) that is derived by combining the average efficiencies in each of three particle size fields. The MERV value is not intended to replace the minimum efficiency curve as the primary data product of the MOT. However, it provides marketers and specifiers an easy handle to specify the general range of efficiency required for specific tasks. Compliance to specifications and final selection or comparison should be based on the actual minimum efficiency performance curve.
Testing and standards Since effective filtration plays a significant role in maintaining a high-efficiency HVAC system, it’s important to regularly test systems to ensure maximum performance in relation to green building standards. One way to test filtration efficiency is by using ASHRAE Standard 52.2, Method of Testing General Ventilation Air Cleaning Devices for Removal Efficiency by Particle Size, and ASHRAE is also developing Standard 145P,
• The method of test (MOT) employs a controlled laboratory generated aerosol (Potassium Chloride salt)—this enables accuracy and reproducibility from test to test and laboratory to laboratory. • The MOT provides the minimum efficiency curves of filters over a particle size range of 12 size bands, from 0.3 to 10 micrometers in size—this allows the selection of the desired filtration efficiency against a known particle size of concern. • The MOT documents the minimum efficiency curves of filters through six stages of loading – this avoids the fiction of “averaging” and provides the “worst case” experience over the entire loading cycle. • The MOT summarizes the above data into a single combined curve as the primary data product that typifies the minimum efficiency of a filter—this enables the simple reporting of the efficiency performance. As stated in its position paper on IAQ, ASHRAE is committed to the goals of design, operation and maintenance of systems that provide comfortable and healthful indoor environments in buildings consistent with most effective energy use. The Society’s accomplishments in improving IAQ depend upon the assistance and participation of practitioners from around the world. ASHRAE invites active participation in the Society’s activities – research, standards and conferences – to share knowledge and to further advance the arts and sciences in this important area.
•
About the author Terry E. Townsend, P.E., Fellow ASHRAE, is 2006-07 president of ASHRAE. Professionally, he is president, Townsend Engineering Inc., Chattanooga, Tennessee, and Panama City, Florida. He oversees design of heating, ventilation and air-conditioning, plumbing and sprinkler systems, energy studies and construction management for commercial, institutional and industrial buildings.
31/01/2007 09:17:22
Featurestory Cover
Filtration+Separation January/February 2007
Indoor air quality:
Clean, green HVAC machine S
o much depends on the air we breathe – our happiness, comfort and our health. Terry Townsend from ASHRAE says that not only does filtration play an important role in keeping air clean and creating a healthy indoor environment, but it also plays an important role in sustainable design.
Indoor air quality affects our quality of life – and our bank accounts – so it’s no wonder that building owners and occupants pay attention to the quality of air in our buildings, as a building’s air quality can have a huge impact on its occupants, especially in the workplace. It’s so important that several years ago, a World Health Organization working group concluded that “under the principle of the human right to health, everyone has the right to breathe healthy indoor air.”
related to the temperature, draft, humidity and odours in a building. Some of the most common building-related health complaints include eye, nose and throat irritation; upper respiratory symptoms; and skin irritations and rashes. Such symptoms together comprise what is commonly referred to as “sick building syndrome.” Improving indoor air quality can be a complicated task, given that so many
components are involved in its creation. As recognized in ANSI/ASHRAE Standards 62.1, Ventilation for Acceptable Indoor Air Quality, and 55, Thermal Environmental Conditions for Human Occupancy, IAQ depends on HVAC systems; properly selected, positioned and installed vapour retarders in building envelopes; pollutant source control; building occupants and
The good… So what is good indoor air quality? It’s difficult to precisely quantify but the environmental result is obvious. When a building has good IAQ, its occupants are able to work efficiently and comfortably in an environment that is comfortable and free of pollutants. A building is said to have good indoor air quality when it has no known contaminants at harmful concentrations and when 80 percent of occupants express satisfaction with the air. Sources of indoor air pollutants can include building materials, cleaning products, office equipment such as copy machines, HVAC equipment, and people themselves and the personal care products they use. Microbial growth, pathogens and mould can also contribute to a building’s ill effects when there is no proper ventilation in place.
…the bad… Bad indoor air quality’s effect on occupants isn’t superficial – it can cause many tangible symptoms. Discomfort complaints are commonly
fs4401_pg24_27.indd 24
Incoming outdoor air must be cleansed of pollutants in order to maintain a high indoor air quality at all times.
31/01/2007 09:17:02
Cover Feature story
Filtration+Separation January/February 2007
other building systems and components that provide routes of pollutant exposure and migrations. IAQ is even affected by the building’s site and access to sunlight, greenery and noise levels. In light of the given complexity, IAQ improvement will typically involve a combination of controls and measures involving several of these factors and will often include preventative control and remedial practices.
…and the remedy? Ideally, conversations about good indoor air quality would happen at all stages of a building’s life, from design to destruction, and would involve every party responsible for the building’s environment, including designers, builders, engineers, facility managers and building occupants. One good resource is the ASHRAE Guideline 0-2005, The Commissioning Process, which details the process for documentations and sets the foundation for communication about IAQ. However, even when such communication hasn’t taken place from a building’s foundation, there are still many remedial steps that building owners and operators can take to improve indoor air quality in the work place.
Source Control Pollutant source control measures are one of the most effective ways to improve indoor air quality. One easy way to begin is to isolate or consolidate contamination sources such as office equipment. By locating them all in one area, the contaminants can be more easily contained and ventilated. Other indoor air contaminants, such as outgassing, can be controlled simply by avoiding use of highemitting construction and furnishing materials such as particleboard and some carpeting and wall coverings. Although some products, such as carpet made from recycled tire products and insulation made from recycled cellulose, might be labelled as “green,” be aware that they can often have very high outgassing output and can be a large contributor to bad indoor air quality. • Be cognisant of occupant activities, and designate certain well-ventilated rooms for activities that may have a negative impact on indoor air quality. • Outdoor air can also act as a pollutant source, so use high-efficiency particulate and gas-phasing air cleaning. • Avoid cross-contamination from building exhaust into the building’s air intake.
HVAC System A building’s HVAC system is absolutely critical to its indoor air quality. After all, the purpose of an HVAC system is to provide for the occupants’ comfort and
fs4401_pg24_27.indd 25
health, which is the aim of good indoor air quality. An HVAC system must be properly designed, installed, commissioned, operated and maintained to produce maximum results and to prevent sick building syndrome from occurring. Ventilation is naturally a large part of an HVAC system and also of creating a healthy indoor environment. ASHRAE Standard 62 serves as the basis for almost all of the ventilation requirements contained in North American building codes. “While ventilation is not the only determinant of IAQ, occupants’ perception of air quality and health outcomes typically improve as ventilation rates increase,” says H.E. “Barney” Burroughs, a filtration expert and former ASHRAE president. At the very least, minimum ventilation rates as recommended in ASHRAE Standard 62.1 need to be maintained, but establish minimum ventilation rates based on the building’s needs and not by design occupancy, Burroughs recommends. • Consider the activities in the office to determine of rates above the minimums required by 62.1 need to be enacted. • Do not over-ventilate the office environment in the name of being “green.”
25
To ensure maximum efficiency, there should be continuous monitoring of the ventilation and humidity control systems as well as vigilant water and moisture control. HVAC system efficiency will also benefit from semiannual monitoring, testing, adjusting and rebalancing. Prior to any construction or remodelling, systems should also be flushed out, and construction should be isolated from buildings occupants by space, time or barriers to minimize infiltration of pollutants into the workspace. Remember that temperature control in offices is extremely important as well. If an office environment is either too hot or too cold, workers will be uncomfortable, and productivity will then suffer. ASHRAE recommends that office temperatures be set between 68-74°F in the winter and between 73-79°F in the summer to satisfy the majority of people in the workplace.
Keeping HVAC clean and green Air filtration first came to prominence in 1943 with creation of the HEPA. According to Burroughs, air filters’ original purpose was to protect HVAC systems’ heating elements from heat damage and flames caused by
• Monitor carbon dioxide levels and employ demand control to increase ventilation when needed and only for the actual occupancy of the building.
Operations and Maintenance Maintenance is extremely important to IAQ, and the lack of it can be quite costly. The costs associated with ill health and productivity loss can be far greater than the savings created from not performing needed maintenance. Instead of performing reactive maintenance, implementing a preventative maintenance system can greatly contribute to a building’s IAQ. Even in a building’s planning and design stages, building operators should consider the location of the HVAC system to allow for easy accessibility for cleaning and maintenance.
A company’s air filtration strategy must look at the needs of the staff as well as the technical possibilities.
31/01/2007 09:17:13
26
Featurestory Cover
Filtration+Separation January/February 2007
Test Methods for Gas-Phase Air Cleaning Equipment. Standard 52.2 establishes minimum efficiencies for filters and provides information on the performance of specific filters, allowing designers and operators to choose filters based on the contaminants found in a building. The standard also addresses the filter’s resistance to airflow. The standard uses mandatory language, which enables it to be referenced by other documents that are to be codified, such as Standard 62 and can be used to more accurately compare filtration products, predict their performance and select an air filter based on its efficiency for a specific situation. Other features include:
A selection of filter media used in indoor air applications.
the accumulation of lint, hair and other particulate matter. As air conditioning systems became more popular, the air filter took on the additional role of protecting cooling coils and the system in general to improve efficiency and increase equipment longevity while decreasing maintenance costs. Filtration and gaseous air cleaning within HVAC systems can strongly influence indoor pollutant levels. Anyone who has worked in an office during the ‘flu season’ knows the importance of filtration to keep virus and bacteria levels at a minimum and other tasks relating to IAQ. Filtration can be a local substitute of sorts for ventilation, as it allows local source control and enables contaminant control by occupants at lower cost than dilution because of the energy savings. Not only should incoming outdoor air be cleansed of pollutants, but exhausted air should be filtered as well to prevent cross contamination of air uptake. ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality, should be followe d at a minimum. Be sure to take the following steps in the workplace: • Use medium-efficiency particulate filters to protect heat exchange and distribution systems and to avoid feeding biological growth. This will also cut down on maintenance costs. • Use high-efficiency particulate filters to control disease-bearing organisms and inhalable particulate matter. • Use high-efficiency gaseous filters to control organic and inorganic compounds. In the best filtration plans, everything should be documented to help in analyzing trends and possible contaminant sources within the office.
fs4401_pg24_27.indd 26
Green buildings for clean air Filtration has a definite role in green building criteria. ASHRAE’s definition of a green building notes that a green building should have maximum indoor environmental quality, and filtration contributes to such. In rating systems such as the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED), credits are available for use of (at least) MERV 8 filters during construction and MERV 13 filters during normal operation. To simplify the general screening and selection process for users, the committee that wrote the standard derived a shortcut “handle” to communicate the general category of efficiency performance. This is the minimum efficiency reporting value (MERV) that is derived by combining the average efficiencies in each of three particle size fields. The MERV value is not intended to replace the minimum efficiency curve as the primary data product of the MOT. However, it provides marketers and specifiers an easy handle to specify the general range of efficiency required for specific tasks. Compliance to specifications and final selection or comparison should be based on the actual minimum efficiency performance curve.
Testing and standards Since effective filtration plays a significant role in maintaining a high-efficiency HVAC system, it’s important to regularly test systems to ensure maximum performance in relation to green building standards. One way to test filtration efficiency is by using ASHRAE Standard 52.2, Method of Testing General Ventilation Air Cleaning Devices for Removal Efficiency by Particle Size, and ASHRAE is also developing Standard 145P,
• The method of test (MOT) employs a controlled laboratory generated aerosol (Potassium Chloride salt)—this enables accuracy and reproducibility from test to test and laboratory to laboratory. • The MOT provides the minimum efficiency curves of filters over a particle size range of 12 size bands, from 0.3 to 10 micrometers in size—this allows the selection of the desired filtration efficiency against a known particle size of concern. • The MOT documents the minimum efficiency curves of filters through six stages of loading – this avoids the fiction of “averaging” and provides the “worst case” experience over the entire loading cycle. • The MOT summarizes the above data into a single combined curve as the primary data product that typifies the minimum efficiency of a filter—this enables the simple reporting of the efficiency performance. As stated in its position paper on IAQ, ASHRAE is committed to the goals of design, operation and maintenance of systems that provide comfortable and healthful indoor environments in buildings consistent with most effective energy use. The Society’s accomplishments in improving IAQ depend upon the assistance and participation of practitioners from around the world. ASHRAE invites active participation in the Society’s activities – research, standards and conferences – to share knowledge and to further advance the arts and sciences in this important area.
•
About the author Terry E. Townsend, P.E., Fellow ASHRAE, is 2006-07 president of ASHRAE. Professionally, he is president, Townsend Engineering Inc., Chattanooga, Tennessee, and Panama City, Florida. He oversees design of heating, ventilation and air-conditioning, plumbing and sprinkler systems, energy studies and construction management for commercial, institutional and industrial buildings.
31/01/2007 09:17:22