Key Strategies for Improving Indoor Air Quality in Homes
INDOOR AIR QUALITY IMPROVEMENT, KEY STEPS - CONTENTS: Key steps in improving indoor air quality - What are the Best Ways to Improve Indoor Air Quality ?Removing or keeping out indoor contaminants - Source Control Strategy to Reduce Indoor Contaminants. Whole-House Ventilation Strategy to Improve Indoor Air Quality. Spot Ventilation Strategy to Reduce Indoor Contaminant. Home ventilation strategies - Air Cleaning Strategy for Improving Indoor Air Quality: Minimum fresh air requirements & standards for buildings, and Best methods for cleaning & filtering indoor air
4. Air cleaning: Filter indoor contaminants out of the air using filters and air handling equipment
See AIR FILTERING STRATEGIES
Source Control Strategy to Reduce Indoor Contaminants
The most effective way to avoid a
household hazard is not to bring it into the house in the
first place. In the case of building materials, this typically
requires a material substitution.
For example, one of the
most common indoor air pollutants is formaldehyde,
widely used in wood composites such as particleboard,
hardwood plywood, and medium-density fiberboard
(MDF). If acceptable substitutions can be found at an
affordable price, the problem is solved. Another example
is fiberglass duct board, which releases small amounts of
fiberglass, a lung irritant, into the air stream. Use rigid
metal ducts or flexible metal-lined duct instead.
In cases where there is no acceptable alternative,
look for ways to seal the chemicals in. For example, medium-density fiberboard (MDF) that is sealed on all six
sides by plastic laminate, as is the case on some laminated
cabinets, emits only low levels of formaldehyde. In general,
a material that is impervious to water vapor can
effectively block formaldehyde emissions.
Combustion devices are another major source of both
gases and particulates. To keep emissions to a minimum,
avoid the use of fireplaces, woodstoves, and unvented
combustion appliances, including gas stoves and heaters.
If gas cooking is desired, select a unit with a pilot-less
ignition. Also, substitute sealed-combustion appliances
for atmospherically vented heating, ventilating, and air-
conditioning (HVAC) equipment. This eliminates the possibility
of flue-gas spillage and usually has higher efficiency
ratings as well.
Other steps that can have a big impact on indoor
air involve lifestyle changes that are decidedly low-tech,
including the following:
Close windows when outdoor air is full of pollen or
Remove footwear at the entry to prevent spreading
pesticides, lead, biological materials, and a wide range
of pollutants around the house.
Avoid bringing strong chemicals into the home for
cleaning or hobbies.
Keep smoking, pets, workshops, and other sources
of pollutants and allergens out of the main living
Minimize the use of dust-collecting surfaces such as
carpeting, open shelves, and upholstered furniture.
Vacuum frequently with an efficient vacuum cleaner.
If allergens are a concern, use a HEPA vacuum or a
central vacuum that vents to the exterior.
Spot Ventilation Strategy to Reduce Indoor Contaminants
Some pollutants are created by our
daily living patterns. It is far more effective to exhaust
these directly at the source than to try to remove them after
they are distributed throughout the household air.
The most common examples are kitchens and bathrooms.
Both produce large amounts of water vapor, not a
pollutant in itself, but a contributor to other problems.
Too much moisture in the air significantly increases
formaldehyde emissions and can lead to mold and mildew
An effective range hood also removes atomized
grease, particulates, and, in the case of gas ranges and
cooktops, combustion by-products. For details, see “Kitchen
and Bath Ventilation,” page 260.
Spot ventilation is also important for darkrooms and
other hobby areas that can produce high concentrations of
chemical fumes. Home offices with high-capacity laser
printers or photocopiers can also generate enough pollutants
to justify spot ventilation.
Whole-House Ventilation Strategy to Improve Indoor Air Quality
is designed to provide a low level of fresh air to all habitable
spaces, particularly bedrooms and main living areas, and to help flush out the low levels of pollutants generated
by occupants, pets, and building materials.
and pets produce moisture, carbon dioxide, and
odors. In addition, most homes have a certain amount of
chemical and biological pollutants from pets, cleaning,
and hobbies and from outgassing from paints, plastics,
pressed wood products, fabrics, and other household
Whole-house ventilation is not meant to take the place
of spot ventilation, which is still required to exhaust concentrated
pollutants from cooking, bathing, and hobby
Although not yet required in most current building
codes, whole-house ventilation is being incorporated
into more and more new homes, and is recommended by
model energy codes and standards organizations, such as
the American Society of Heating, Refrigerating, and Air-
Conditioning Engineers (ASHRAE) and the National Fire
Protection Association (NFPA).
Operating costs. It is important to note that mechanical
ventilation costs money both to operate the fans
and to heat or cool the incoming fresh air. To provide
the recommended ventilation levels, using an efficient
fan in either an exhaust or supply system, the annual
cost for a 1,500-square-foot house ranges from about
$150 to $200 per year, depending on climate and fuel
Heat-recovery ventilators (HRVs) have higher
electrical costs with dual fans but save money
through heat reclamation, so annual energy costs
New homes. Plan to run the ventilation system at high
speed for at least the first few months of occupancy,
since paints, plastics, pressed wood products, and
many other materials will outgas at their greatest rate
during this period. If the house still smells of fresh
paint or new carpet, volatile organic compound (VOC)
levels are still too high.
Air Cleaning Strategy for Improving Indoor Air Quality
Air cleaning is the least effective strategy
for maintaining a healthy indoor environment, but it can
play a role along with source control and ventilation. There
are many different types and sizes of air filters on the
market, both portable units and filters integrated into
the home’s HVAC system. Situations that may call for air
cleaning equipment are:
Where the outside air is polluted or full of pollen and
needs to be filtered before bringing the air into the
Homes with high pollutant sources, such as tobacco
smoke or certain hobbies.
Individuals with asthma, allergies, or chemical
Homes with high levels of indoor dust, for example pets shedding hair and dander, a building in a dusty environment, and where finding a new home for the pets or moving out of the dusty environment are not options.
Building Fresh Air Requirements - 15 cfm per person
The U.S. EPA recommends an outdoor fresh air supply of at least 15 cfm per person.
In occupied buildings, especially offices and other locations with multiple occupants, we like to take a look at the carbon dioxide level as one means to check for inadequate fresh air intake for the building.
See CARBON DIOXIDE - CO2.
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