Panasonic Brochure

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stale air and provide fresh air on a slow,
continuous basis. A well-designed airtight
home can generally use low volume
continuous ventilation.
Intermittent Ventilation
Sometimes referred to as spot, local
or secondary ventilation, intermittent
ventilation is used to capture and remove
pollutants quickly at the source. Pockets
of excessive moisture and pollutants
can build up in the bathroom, kitchen,
utility room, garage and home office. This
secondary process serves to exhaust
these problem areas quickly, before bad
air can spread throughout the house. Just
as important as continuous ventilation,
intermittent ventilation complements the
effort to improve indoor air quality.
Both systems exhaust pollutants from
the air, but intermittent ventilation is more
effective in concentrated areas.
Sizing Information and Instructions
Properly sized ventilation in airtight homes
helps to ensure healthy indoor air quality.
Both intermittent (spot) and continuous
(whole house) ventilation should be
considered. Intermittent ventilation is
used to exhaust sources of moisture
and odors, while continuous ventilation
is used to remove accumulated indoor
air pollutants.
Airtight Homes
The first step when sizing for a ventilating
fan is to determine the application. Decide
whether you are sizing for intermittent
or continuous ventilation (see pages 6
and 7). If intermittent, determine which
application, (i.e. bathroom, kitchen
or other). Use the following industry
recommendations to determine Air
Changes per Hour (ACH) for your specific
application.
Intermittent (spot) ventilation:
The Home Ventilating Institute (HVI)
recommends the following Air Changes
per Hour (ACH). (See HVI on page 43)
I. Bathrooms - 8 ACH or 1 CFM/sq ft
II. Kitchens - 15 ACH or 2 CFM/sq ft
III. Other Rooms - 6 ACH or .75 CFM/sq ft
Continuous (whole house)
ventilation:
Most building codes have adopted
the American Society of Heating,
Refrigerating, and Air Conditioning
Engineers (ASHRAE) Standard 62. The
most current version, ASHRAE 62.2-2010,
calls for continuous mechanical ventilation
as shown below.
I. House or apartment - 7.5 CFM per
person plus 1 CFM per 100 square feet
The second step is to calculate the area
being ventilated. Calculate square feet
or cubic feet depending on which sizing
method you choose.
The third step is to calculate the
Equivalent Duct Length of the planned
duct run. This requires a basic
understanding of static pressure caused
by a duct run design and its components.
Static Pressure and Duct Run: A
ventilating fan must overcome resistance
when pulling air through the grille and
pushing it through the duct and cap to
the outside of the building. This resistance
is known as static pressure. The amount
of static pressure depends on the duct
length, type of duct, elbows and the roof
jack or wall cap.
Why is ventilation
necessary?
Ideally, an airtight home designed with both continuous and intermittent ventilation will
contribute to a healthy and comfortable living environment for the entire family.
Today’s homes are designed and built
to improve energy efficiency. However,
these airtight homes may actually cause
health problems due to the build-up
of pollutants and uncirculated stale
air. What do they need? Mechanical
ventilation!
Airtight Homes
Homes designed and built in recent years
are more airtight and energy efficient than
in the past. To obtain this airtight design,
house wraps, newly designed windows
and doors, sealing caulks and other
insulating materials are used to create
better energy efficiency. The resulting
benefit is fewer drafts, which lowers the
cost to heat and air-condition a home.
But pollutants retained in airtight buildings
can be hazardous to their occupants
and can jeopardize structural integrity.
That’s why Panasonic stresses a “build
tight and ventilate right” platform. Proper
mechanical ventilation design can address
poor indoor air quality, while retaining
energy efficiency.
Biological Pollutants
Biological pollutants, to some degree, are
found in all homes. These include mold,
mildew, pollen, dust mites, pet dander,
viruses and bacteria. Accumulation of these
biological pollutants can result in hazardous
health effects for the occupants, as well as
structural damage to the building.
Volatile Organic Compounds (VOCs)
Volatile Organic Compounds are carbon-
based compounds that easily evaporate.
Formaldehyde and these types of gases
are released from building materials,
carpets, furniture and many other
solid household items as part of aging,
decomposition or curing, all of which are
natural processes known as off-gassing.
Some other household items that emit
VOCs include hair sprays, paints, lacquers,
finishes, oven cleaners and other cleaning
solvents, pesticides, etc. Often colorless
and odorless, VOCs can ultimately
sensitize certain people to react to them.
Ways to improve indoor air quality
The first step to improve indoor air quality
should be to reduce or remove the
source of the pollutants.
Unfortunately, indoor pollutants are
virtually impossible to eliminate completely,
creating the need for a second step to
improve indoor air quality—mechanical
ventilation. Mechanical ventilation is used
to remove stale, moist, polluted air and
replace it with fresh outside air. Two widely
used methods in today’s building industry
are continuous and intermittent ventilation.
Continuous Ventilation
Sometimes referred to as general, central,
whole-house or primary ventilation,
continuous ventilation is used to remove
Bad
Pollutants such as smoke, formaldehyde,
dust, humidity and VOCs accumulate in a
poorly vented building.
Good
Ventilation fans help to maintain
indoor air flow and air quality.