HVACR416 - Design

Introduction to IAQ

What is Indoor Air Quality

• Indoor air quality (IAQ) is a term used to describe the indoor climate of a building.

• The main concern of this climate is the impact on the occupants health and comfort.

What is indoor air quality

• Indoor air quality includes the following:

o Humidityo Temperatureo Purityo Speed (drafts)

• Thus, indoor air quality speaks to the air in the building compared with the air outside.

Indoor Environmental Quality

• Indoor environmental quality takes the thought of IAQ a step further and speaks to additional issues which affect occupant comfort and health.

• Environmental issues include:o Lightingo Noiseo Ergonomic Stressorso Overcrowding (also an IAQ issue)o Psychosocial stress

Why is everyone so concerned?

• Over the years there has become a greater awareness of Indoor Air Quality (IAQ) this is due to a number of issues such as:

o People spending more time indoorso Tighter building constructiono Greater awareness

Media Litigation

o More indoor pollutants Office equipment in both homes and work More synthetic material

What affects the indoor environment?

• The indoor environment in any building is a result of the interaction between:

o The site

o The climate

o The building (as a system)

o Construction techniques and quality

What affects the indoor environment?

• Sources of contaminationo Building materialso Furnishingso Moistureo Activities and processes in the buildingo Building occupants

IAQ Problems

• All IAQ problems are broken down into four elements:

o Source – there must be a source of all contamination or discomfort indoors, outdoors, or within the mechanical systems of a building.

o HVAC – the HVAC system is not able to control existing air contaminants and ensure thermal comfort (temperature and humidity conditions that are comfortable for most occupants).

IAQ Problems

• Pathways – One or more pollutant pathways connect the pollutant source to the occupants and a driving force exists to move the pollutants along the pathway(s).

• Occupants – Building occupants are present. The pollutants have to affect someone or something.

• To understand IAQ issues you must understand the role each of these plays in the contamination and complaint.

Sources of Contaminants

• Indoor air contaminants can originate within the building or be drawn in from outdoors

• If contaminant sources are not controlled, IAQ problems can arise even if the HVAC system is properly designed and well maintained.

Sources of Contaminants

• Outside Sources

o Contaminated outside air such as pollen, dust, fungal spores, industrial pollutants, general vehicle exhaust.

o Emissions from nearby sources such as cares on nearby roads, parking garages, loading docks.

o Odors from dumpsters, exhaust from the building itself or from neighboring buildings.

o Poorly placed outdoor air intakes.

Sources of Contamination

• Outdoor Sources Continued

o Soil gasses such as radon, leakage from underground fuel tanks, contaminants from prior uses of the site.

o Pesticides

o Landfills

o Moisture or standing water around or on a building (rooftop after rain) that promote microbial growth.

Sources of Contamination

• HVAC System

o Dust or dirt in ductwork and filterso Dirty coils in air streamo Microbiological growth (like mold) in drip pans,

humidifiers, ductwork, coils.o Improper use of biocides, sealants, and cleaning

compoundso Improper venting of combustion productso Refrigerant leakage

Sources of Contamination

• Non-HVAC Equipmento Emissions from office equipment (VOC’s or volatile

organic compounds).o Emissions from office supplies (toner, solvents,

cleaning supplies)o Elevator motors and other mechanical equipment

Sources of Contamination

• Human Activitieso Personal activities such as smoking, cooking, or body

odoro Cosmetic odors

o Housekeeping activities such as cleaning materials and procedures.

o Emissions from stored cleaning supplies

o Maintenance activities such as airborne dust or dirt, painting, pesticides (both in use and stored)

Sources of Contaminants

• Building components and furnitureo Locations that produce dust and fiber such as couches,

carpets, and curtains.o Old furniture

o Unsanitary conditions and water damageo Dry-traps that allow the passage of sewer gasses.

o Chemicals released from building components or furniture (VOC’s)

Sources of Contaminants

• Other sources:

o Accidental events such as spills of water or other liquids.o Microbiological growth due to flooding or leaks from the roof or

pipes.o PCB’s from electrical equipment that has been damaged.

o Special use areas such as smoking areas, laboratories, print shops, art rooms, auto shops, exercise rooms, beauty salons, and food preparation areas.

o Remodels (VOC’s)

Sources of Contaminants

• It is important to remember that indoor air often contains contaminants that are well below the standards or guidelines for occupational exposure.

• We also, at this time, lack the scientific knowledge on the results of this low level pollutant exposure.

• It is important to document and be honest in your discovery of any pollutants and not scare the occupants into doing repair or remediation work.

The HVAC System

• The HVAC system includes:

• All heating, cooling, and ventilation equipment servicing the building:

• Boilers• Furnaces• Chillers• Exhaust fans• Ductwork• Filters• Water and steam piping

The HVAC System

• The HVAC system could be a central system or a series of stand-alone components.

The HVAC System

• A properly designed HVAC system:

• Provides thermal comfort

• Distributes adequate amounts of outdoor air to meet the ventilation needs of all building occupants

• Isolates or removes odors and contaminants through pressure control, filtration, and exhaust fans.

What is thermal comfort?

• There are a number of variables that determine if people are comfortable with the temperature of the indoor air. It is possible that no two people in a building will have the same comfort levels.

• The activity level, age, and physiology of each person affects the thermal comfort levels.

• The American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHREA) standards 55-1981 describes the temperature and humidity ranges of people engaged in largely sedentary activities.

What is thermal comfort?

• The ASHREA guidelines assumes “normal” indoor clothing. Additional layers of clothing reduces the rate of heat loss.

• Uniformity of temperature is important to comfort.

• Large rooms controlled by a single thermostat may have various temperatures in the room.

• Airflow directly from ducts and registers may create drafts.

What is thermal comfort

• Radiant heat transfer may cause people located near very hot or very cold surfaces to be uncomfortable even though the thermostat setting and the measured air temperature are within the comfort range.

• Humidity is a factor in thermal comfort. Raising relative humidity reduces the ability to loose heat due to perspiration and evaporation so that the effect is similar to raising the temperature.

What is thermal comfort

• Humidity extremes can cause other problems as well.

• Excessively high or low humidity can cause discomfort.

• Excessively high humidity can promote the growth of mold and mildew.

What is thermal comfort?