Do I Need An Air Exchanger?
a startling fact.
70,000 Americans die each year from Dirty Air... Millions more are
hospitalized or sickened...
Indoor Air Quality is often worse than polluted outside air...
According to the EPA; concentrations of toxic pollutants can be up to ten
times greater inside a home than outside, even in our smoggiest cities. And
today's homes, while more energy efficient, can trap contaminants like
formaldehyde, radon, and household chemicals inside.
Invisible pollutants produced by common household substances, plus dust and
excess humidity that get trapped in today's houses, can increase your risk
of chronic respiratory illness and your home's risk of serious structural
Today's well-insulated homes often lack the ability to "breathe" freely.
Trapped, stale air and excess humidity can lead to mould build-up,
unpleasant odours, condensation on windows, and even structural damage to
More than 50% of all homes show signs of high basement humidity.*
*Source: Canada Mortgage and Housing Corporation (CMHC)
Dust, Chemicals, Aerosols and Other Common Pollutants
Pervasive irritants such as dust, dust mites, cigarette smoke and other
pollutants commonly found in household air may increase the risk of chronic
respiratory illness, allergies, sinusitis, frequent headaches, coughing and
The rate of asthma has increased by 160% over the last 15 years.*
Primary Sources of Indoor Air Pollution
The word pollution is often associated with large clouds of smoke emerging
from factory smoke stacks, automobiles, etc. In fact, the majority of people
blame poor indoor air quality on outdoor air pollution. But this is not
true! Outdoor air pollution only counts for a fraction of indoor air
These Are The Main Sources Of Indoor Air Pollution:
Asbestos, Insulation, Fiberglas, Dust
& Dust Mites
Humidity Levels, Unpleasant Odours, Mould, Carbon
Monoxide (CO), Fireplace/Smoke, Firewood, Radon,
Solvents, Woodstove, Dust & Dust, Mites, Combustion
System, Paints & Chemicals, Household Cleaners
Humidity, Personal Hygiene, Products (Aerosols, Sprays,
Etc.), Mould Spores
Carpet, Dust & Dust Mites, Pet Hair and Dander,
Carbon Dioxide (CO2)
Photocopiers: Ozone, Volatile Organic Compounds (VOC),
Melamine Furniture (Harmful Vapours, VOC, And
Monoxide (CO), Gas, Pesticides/Herbicides, Solvents,
Dust, Paints & Chemicals, Cleaning
Fireplace, Dust & Dust Mites, Allergens, Second-Hand
Smoke, Humidifiers, Pet Hair and Dander
Odours, Bacteria, Cooking Pollutants
Six Essential Steps To Healthy Indoor Air
The Soup Concept
Indoor air is like a soup with a variety of pollutants in it. Most of these
indoor air contaminants are known to cause or contribute to a long list of
health and each of these pollutants requires its own strategic solution in
order to eliminate them from the air you inhale.
It is difficult to write this article knowing that so many of the points
mentioned below could be elaborated on in much greater detail, nonetheless
this short article should serve as a general guide for understanding the
basic steps to cleaner indoor air.
There are six steps in total that must be followed; miss one and you
compromise your indoor air quality and your health. Use the acronym "EFVOID",
to outline these strategic steps:
E = Elimination
Eliminate or reduce as many obvious indoor air pollutant sources as is
reasonably possible. These would include but are not limited to the
following: Un-maintained or very old carpet, especially if laid over
concrete, dust accumulation in air ducts, all visible mould growth no matter
the amount, indoor pesticides, perfumes, hair sprays, animal dander, cat
boxes, unsealed paint cans, indoor smoking of tobacco products, metabolic
sewer gasses from unused plumbing fixtures, candle burning, unencapsulated
man-made building materials, and plug-in, spray, or standing deodorizers
that emit man-made chemicals. Laundry and cleaning products, personal care
products, etc. that you can purchase without chemical fragrances will be
most advantageous to reduce exposure and indoor related health problems.
Many of the indoor air pollutant sources mentioned above are common sense
when given a thought, yet the cumulative affect is often overlooked.
Eliminate as many as you reasonably can. In some cases a professional air
quality inspection may be in your best interest to assure you are not
missing indoor air pollutant sources such as sewer gas entry, small
combustible gas leaks, areas of hidden mould, negative air pressure
problems, or ventilation/heating/cooling failures or inadequacies. This is
especially important for those homes where occupants have already begun
experiencing any of the indoor air quality symptoms listed at
F = Filtration
Use good air filtration. This entails the use and maintenance of quality
furnace, the possible use of high efficiency particulate air filters (HEPA)
in rooms, particularly if you do not have a ducted air handling system, and
lastly, a high quality vacuum cleaner which does not allow ultra-fine
particles to re-circulate back into the air. Reducing airborne particles
with the use of good filtration techniques will improve indoor air quality
by making indoor air less dense of particle pollutants and consequently
easier to inhale. This will also reduce physical irritation that causes
allergy and asthma symptoms. It is additionally important to never feather
dust your home or sweep hardwood flooring. Sweeping and feather dusting
launch massive amounts of particles back into the air. Dust these areas with
damp cloths or mops, or vacuum with a quality vacuum cleaner to prevent
V = Ventilation
The first thing ventilation entails is circulating your indoor air by using
your ducted air handling system (if you have one),
even if you are not air conditioning or heating. Air should be circulated
continuously, or at minimum, at critical times of each day during high
activity when significant amounts of airborne particles are being created
(when people are changing clothes or during high activity periods indoors).
Circulating indoor air helps to scrub airborne particles from your air
(provided you are using quality air filters in your air handling system)
and helps to prevent dead air space and micro climates were mould can take
hold. Circulating your indoor air also helps true air purification systems
to work more efficiently by mixing the air in your indoor environment.
Secondly, ventilation includes opening windows frequently to allow
replenishing of indoor oxygen levels. This is essential because there is
nothing in indoor environments that "makes" oxygen for you. Maintaining good
oxygen levels will help reduce headaches, tiredness and fatigue while
increasing mental alertness and improving overall health. Opening windows
should be done whenever needed, all year long. If the weather is extremely
hot or cold, the indoor air exchange process will be expedited by default.
This is due to the differences in outdoor and indoor air temperatures.
During extreme temperature differences windows can be closed again very soon
after opening them.
Third, ventilation includes the use of exhaust fans to remove bathroom
odours, moisture from showering and cooking, and to reduce exposure to
chemicals in hair spray or other aerosol products.
O = Ozonation
Ozone, also known as "activated oxygen", is one of natures
ingredients for purifying outdoor air and is absolutely essential in the
elimination of indoor pollutants. Indoor ozone levels should be constantly
maintained to the same levels as those found naturally over the entire
planet. Ozone oxidizes chemical gasses and eliminates virtually all odours.
Ozone also helps control viruses, bacteria and mould growth. Ozone is the
primary reason we always go OUT for fresh air and is the sole reason for the
fresh air smell outdoors. Proper indoor ozone replacement can only be
accomplished by using a true air purifier with adjustable ozone output.
I = Ionization
Ions are the second ingredient that nature uses for cleaning the outdoor air
of particulate (physical matter floating in air) and are another essential
for indoor air quality. Indoor ions must be maintained in the right amount,
and in the right ratio of positive ions to negative ions, just like nature
produces outdoors. Ions are effective for indoor particle reduction even if
no filtration is used, albeit you should still use filters if you can. Ions
also work on particles that are so small they would pass through virtually
any man-made filter media and vacuum bags. Furthermore, ions inadvertently
help eliminate odours by reducing odor carrying particles from sources such
as mould spores and airborne fecal and urine matter. Ion replacement is
accomplished by using a true air purifier with constant ion output.
D = Dehumidification
Maintaining indoor humidity levels at or below 50% is absolutely essential
to help protect your indoor air from bio-contaminants such as mould,
bacteria, insects, mites and their related metabolic gasses and excrement.
Most indoor environments today require dehumidification. A humidity gauge is
the only way to know if your humidity is within safe parameters year round.
Follow the six steps above and your indoor air quality will be as good as it
can be. Miss just one of these steps and your air quality will certainly be
degraded or compromised.
Air Exchanger Basics
With the emphasis on energy conservation and efficiency, new home
construction can create a problem of indoor air pollution. Vapour barriers,
thermal windows, weather-stripping and caulk have reduced or stopped fresh
air from infiltrating and replacing stale air. Entering and exiting the
house through doors isn't always enough air changes. Cooking, aerosol
sprays, cleaning agents, paints, and in some cases excess humidity if the
house is sealed too tightly can create an undesirable environment. Keeping
windows or doors open does not conserve energy. A device known as an
air-to-air exchanger is used to recover heating or cooling and improve air
Heat-recovery air exchangers capture heat from stale moist air and transfer
that heat to the fresh air intake so that your heating system will not have
to work so hard to condition that air.
Air-to Air Exchangers
By Building Inspector and Indoor Air Specialist, Dan Schilling
© Copyright 2002 Residential Inspections LLC, All Rights Reserved
Air-to-air exchangers (top left), sometimes called heat recovery ventilators,
may go by different brand names, but they all have the same primary function
of introducing fresh air from the outdoors into the interiors of homes. The
reason they are sometimes called heat recovery ventilators is because they
temper the cold incoming air by extracting heat from the stale air being
simultaneously exhausted. These devices are being heavily promoted and sold
by some HVAC contractors and, in some states, they are an option to fulfill
new construction code requirements designed to improve indoor air
Provided that these devices are diligently maintained, and I repeat
"diligently" maintained, they can be an advantageous appliance to have
installed in a home or office building. On the other hand, air-to-air
exchangers should never be considered a viable solution to the indoor air
contamination problems causing such a wide array of health concerns.
Furthermore, if not consistently maintained, these devices can become
seriously detrimental, increasing the contamination of indoor air.
Allow me to share a list of what I regard as the advantages and disadvantages
of these air-to-air exchangers/heat recovery ventilators.
Air-to-air exchangers bring in small amounts of oxygenated air into a home
on a varying basis, depending on how the system is installed. This influx of
oxygenated air is typically introduced directly into the interior of the air
duct system and then distributed through the ducts. When considering that
each human in a home breathes about 2,500 gallons of air every day, one
begins to understand the benefit of replacing oxygenated air indoors.
Replacing oxygenated air to the indoor environment can help us feel more
energetic, mentally alert, and reduce symptoms associated with high levels
of carbon dioxide (CO2). While carbon dioxide should not be confused with
highly poisonous carbon monoxide (CO), high levels of carbon dioxide can
also cause poor health affects, such as headaches, dizziness, drowsiness,
shortness of breath and eye irritation.
Air-to-air exchangers assist in the removal of indoor moisture which could
lead to mould and bacterial contamination of indoor air. The amount of
moisture actually being eliminated from the indoor environment may be
nominal in comparison to the amount of moisture created within a home,
however, even small amounts of moisture removal are a step in the right
direction. This is particularly true for newly constructed homes and homes
that have otherwise been made more energy efficient.
Rancid indoor air is a serious problem in virtually all indoor environments.
Adding a small percentage of oxygenated air to an indoor environment does
not solve the indoor pollution problems we have today. It is very misleading
to presume that these devices are an answer to indoor air quality.
Contamination sources and elimination methods are very complex and often
require a variety of measures to correct and improve indoor air quality. As
I have said many times before, there is no silver bullet.
Air-to-air exchangers typically will not remove enough moisture from the
indoor air to eliminate moisture related problems, hence, all other methods
of indoor moisture control must still be considered. High levels of moisture
are known to be the leading cause of biological contamination found in
Similar to the evaporator media used in built-in humidifiers and the fins of
the air conditioner evaporator coil (both hidden from view inside duct
work), the media inside of a typical air-to-air exchanger also secretly
collects dust particles. These particles can promote hidden mould growth and
can potentially circulate the mould spores into the breathable air. As an
air quality inspector, I never recommend any unnecessary media that can
promote hidden bio-growth within the air circulation system.
Electrical ions, richly present in the air outdoors and vital to cleaning
ultra-fine particles from the air, are not brought in through air-to-air
exchangers. It is unlikely that the beneficial ions would make it past the
outdoor intake vent, much less through the ducts of the system. Ions lose
their electrical charge the moment they touch something, such as the
interior of ducts or filter media. Therefore, air-to-air exchangers are an
inadequate solution for the removal of particulate pollutants that cause
many ill health affects.
Naturally "activated" oxygen, also called "ozone" (not to be confused with
manmade pollution levels), is also present in the air outdoors and is
necessary for eliminating foul odours and chemical gasses through a process
called oxidation. Ozone is what leaves that fresh, clean smell in the air
outdoors. Air-to-air exchangers may bring in small amounts of activated
oxygen, but not nearly enough to maintain natural outdoor levels for proper
indoor air purification. This is particularly true in new or remodeled homes
where the rate of off-gassing chemicals from building materials is
excessive. Due to the half-life of ozone, one would have to leave all house
windows wide open 24 hours a day in order to maintain the outdoor
purification levels of ozone. This is highly impractical for most of us.
Many are now turning to residential air purifiers as a practical way to
replace the missing ozone. (Note: Air purifiers that produce ozone indoors
should have complete adjustability of ozone output.)
Air-to-air exchangers require regular maintenance, which is almost never
performed by homeowners, and likely to be overlooked by contractors during
service calls. In fact, at the time of this article, I have yet to see one
of these air-to-air exchangers properly maintained while conducting building
inspections. Internal motors do not get oiled, allowing them to dry up, heat
up and seize. The interior filters are not cleaned and, perhaps worst of
all, the air intakes from the exterior are quite frequently clogged with
dirt. Often they are so clogged that an ant couldn't get through, much less
a supply of fresh air. If outdoor air cannot enter, there is no benefit
When the air intake vents (middle left) get clogged (bottom left), these
systems which were intended to improve indoor air quality can become a
detrimental health hazard. When clogged, air-to-air exchangers can make the
indoor air significantly worse than it would be without the system installed
at all. This point should be further emphasized by saying that clogging is a
matter of when, not if. The reason for this has to do with indoor air
pressures: When the intake vent gets clogged and the system can no longer
bring in air from outdoors, it will still continue to exhaust air from the
indoors. This creates "negative air pressure" within the home, which in turn
can cause serious air quality issues due to a process called
"back-drafting". In essence, back-drafting causes critically important
exhaust vents in the home to function poorly, or operate in reverse.
Consequences of negative indoor air pressure and back-drafting are: A)
prevents kitchen and bathroom exhaust fans from operating properly, which
can over tax and burn out their motors faster, B) causes excessive indoor
moisture levels which in turn causes health problems related to moulds and
dust mite populations, C) causes exhaust vents from furnaces, water heaters,
gas ranges and fireplaces to function poorly, or in reverse, thus spilling
poisonous carbon monoxide gasses and other combustion pollutants into
breathable air, D) increases the infiltration rate of radioactive radon gas
through the basement area of a home which increases the risk of lung cancer
for the occupants of the home.
If the interior filter, designed to protect the heat transfer portion of the
system, becomes clogged with house dust, the system can no longer exhaust
the stale indoor air properly. If the system still has the ability to pull
outdoor air into the home without the ability to exhaust an equal amount of
air, the indoor air pressure can become "positive". This positive indoor air
pressure can cause "exfiltration" which pushes moisture-laden indoor air
into the walls of the house, through electrical outlets, switches, light
fixtures, box sills, and floor boards. Consequences of moisture exfiltration
are: A) moisture can accumulate in wall cavities where it can begin rotting
the structural frame of a home, B) the moisture rusts metal plate fasteners
of floor and truss members which can lead to collapse, C) the moisture can
cause the walls and floors to change shape, D) moisture attracts
wood-destroying insects into wall cavities, E) cause paint to peel on
exterior walls, F) moisture can wet and damage insulation causing energy
Note: As you can see, positive indoor air pressure can adversely affect the
structure of your home while negative air pressure adversely affects the
health and safety of the occupants. Ideally, indoor air pressure should be
as close to neutral as possible.
The installed price of an air-to-air exchanger can be $1,500.00 to $3,000.00 each.
In summary, if you bought a home that did not have an air-to-air exchanger, I
would recommend you do not purchase one. For the benefit of a little oxygen,
you could open your windows on occasion, save the maintenance hassles and
use the money for more important air quality improvements. If you bought a
home that already had an air-to-air exchanger, keep it scrupulously
maintained or disconnect it.
Three Better Solutions
In addition to proper cleaning and elimination of obvious sources of indoor
air contaminants, I recommend that homeowners use a combination of the three
proven methods of air quality control listed below. These methods will
significantly improve indoor air quality at a fraction of the cost of an
Efficient Furnace Filters
Good furnace filtration, such as the high-efficiency pleated type or good
quality electrostatic filters will provide:
- A significant reduction of particles in the breathable air,
- Keep the entire house cleaner,
- Help protect mechanical equipment,
- Help prevent mould and bacterial growth in air conditioner coils and,
- Help prevent AC condensate drip pans and drain lines from becoming
clogged and damaging the furnace.
Electronic Air Purifiers
Air purifiers (not to be confused with HEPA room filters or electronic
furnace filters) replace the natural levels of electrical ions and ozone
that are missing from indoor air. These portable systems eliminate house
odours, including those from pets, smoke, mould and building materials, as
well as, help cleanse the air of airborne particles. They require no
installation, and just one machine will purify the air in an average size
Make-up Air Vents
The installation of a make-up air vent will bring small amounts of fresh
oxygenated air into the home while helping to maintain neutral air pressures
indoors. They require virtually no maintenance and use no electricity.