Setting the Standard for Indoor Air Quality

ASHRAE, the American Society of Heating, Refrigeration and Air Conditioning Engineers developed Standard 62.2, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings.  The standard, which is widely accepted by green builders, state and local around the counties, defines the roles of and minimum requirements for mechanical and natural ventilation systems and the building envelope in order to provide acceptable IAQ in low-rise residential buildings.

10 Steps to Ensure Good Indoor Air Quality

1. Vent bathrooms, kitchens, toilets and laundry rooms directly outdoors.  Use energy efficient and quiet fans.
2. Avoid locating furnaces, air conditioners and ductwork in garages or other spaces where they can inadvertently draw contaminants into the house.
3. Properly vent fireplaces, wood stoves, and other hearth products; use tight doors and outdoor air intakes when possible.
4. Vent cloths dryers and central vacuum cleaners directly outdoors.
5. Store toxic or volatile compounds such as paints, solvents, cleaners, and pesticides out of the occupiable space.
6. Minimize or avoid unvented combustion sources such as candles, cigarettes, indoor barbecues, decorative combustion appliances or vent free heaters.
7. Provide operable windows to accommodate unusual sources or high-polluting events, such as the use of home cleaning products, hobby activities, etc.
8. Use sealed-combustion, power-vented or condensing water heaters and furnaces.  When natural-draft applications must be used, they should be tested for proper venting and should be located outside the occupied space when possible.
9. Put a good particle filter or air cleaner in your air handling system to keep dirt out of the air and off your ductwork and heating and cooling components.
10. Distribute a minimum level of outdoor air throughout the home using whole-house mechanical ventilation.

Source: ASHRAE Standard 62.2 Ventilation and Acceptable Indoor Air Quality on Low-Rise Residential Buildings, and 2001 ASHRAE Handbook, Fundamentals, Chapter 26, Ventilation and Infiltration.

Identify and Remove Pollutant Sources

The relative importance of any single source depends on how much of a given pollutant it emits and how hazardous those emissions are.  Educate yourself on the different types of biological, gas, or particulate pollutants that can potentially affect your indoor air quality and takes steps to remove them.  To have a greater understanding of potential indoor pollutants read “Understanding Indoor Air Pollutants“.

Improve Air Ventilation

If too little outdoor air enters a home, pollutants can accumulate to levels that can pose health and comfort problems.  Most home heating and cooling systems, including forced air heating systems, do not mechanically bring fresh air into the house.  When weather permits open windows to increase ventilation.  If you are intending to filter the outside air consider improving your heating and cooling system by having it modified to draw filtered outside air

Improve Filtration

There are many types and sizes of air filters and air cleaners on the market.   As air is circulated through a forced air ventilation system debris is trapped within the furnace filter. Use furnace filters with a MERV rating between 7 to 11, and change the filter every 2 months that the filter is in use.  If a standalone filtration device is used, use a device that has a high-circulation rate and highly efficient filter.

Understanding Air Pathways

Air flow is created by pressure differentials.  Air flow always flows from higher relative pressure to lower relative pressure.  Air will flow through any available opening (pathway) in an attempt to equalize pressure.  Pathways include windows, doors, electrical outlets, floor drains, heating and cooling systems, and most importantly air ducts.

Air Pathways within a Home

A forced air system works by creating a difference in pressure between the area where the supply registers are located and the area where the returns are located.  As air moves from supply diffuser to return air grill, it is diverted or obstructed by partitions, creating pathways of air movement throughout the home.

How do Air Pathways affect a Home?

Pathways can change from one minute to the next – Opened windows, an exhaust fan, open/closed doors etc… Unintended pathways need to be acknowledged to have a comprehensive understanding of a homes airflow patterns.

Improving Air Pathways

Air ducts are the pathways for energy efficient homes.  With a couple of simple steps you can improve your air pathways.

• Seal the air ducts to prevent costly, conditioned air flow from being drawn from or escape into unknown, unspecified, or unintended areas of the home.
• Filter the air by changing the furnace or air conditioning air filter.
• Make sure that air ducts are not blocked by interior furnishings that prevent their designed use.
• Have the air ducts cleaned to prevent obstructions in air flow.
• Use bathroom exhaust fans when using the shower to exhaust moisture.
• Use kitchen exhaust fans when cooking to exhaust fumes from cooking.
• Have your HVAC technician inspect exhaust flues when they perform annual HVAC inspections to ensure carbon monoxide is properly exhausted.

Pressurization

Air flow is created by pressure differentials.  Air flow always flows from higher relative pressure to lower relative pressure.  If more air is supplied to a room than exhausted, the excess air leaks out of the space and the room is said to be under Positive Pressure.  If less air is supplied than exhausted, air is pulled into the space and the room is said to be under Negative Pressure.

Positive Pressure

If a home or building has too much positive air pressure, it will allow for conditioned air to escape the home causing costly energy concerns.

Negative Pressure

Negatively pressurized homes allow for unconditioned and unfiltered air to be drawn within the home or building.  Debris will enter through cracks and crevices, opened doors, windows, etc…

What’s the Ideal Air Pressurization?

It is ideal to achieve neutral to slightly positive air pressurization.  Though there is a slight loss of conditioned air, a slightly positive pressured home will provide comfort and prevent outdoor contaminants from entering the home or building.

ASHRAE Standard 62.1 “Ventilation for Acceptable Indoor Air Quality” requires proper ventilation and a slightly positive pressurization of buildings. Maintaining a small positive air pressure, relative to the outdoors, limits the entrance of outdoor moisture and is a very common strategy to prevent mold and mildew formation in a building.

How Can You Monitor or Control Air Pressurization?

Air pressure can be monitored through an energy auditor.  An energy auditor will use of a blower door & smoke test to determine the location of air leaks.  After the test is performed steps can be made to improve air pressurization.