Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
METHOD FOR REDUCING STACK EFFECT IN A HOUSE
FIELD OF THE INVENTION
The present invention relates to Heating, Ventilation and Air Conditioning
(HVAC)
technologies. In particular, the present invention relates to a method of
reducing the
phenomenon known as the 'stack effect' in a house with or without a combustion
appliance.
BACKGROUND OF THE INVENTION
Often, a wood stove or the like having a chimney stack is installed in a
dwelling as an auxiliary
source of heat. A common frustration with such devices is that the fuel does
not always burn
to complete combustion. As a result of the stack effect, the house may
experience air being
drawn out by outside wind forces causing the flames in the wood stove to not
bum the fuel to
complete combustion. Accordingly, this impedes air flow into the wood stove,
and
subsequently, impacts the efficiency of combustion of the fuel.
Stack effect is the movement of air into and out of buildings, chimneys, flue
gas stacks, or other
containers, resulting from air buoyancy. Buoyancy occurs due to a difference
in
indoor-to-outdoor air density resulting from temperature and moisture
differences. The result
is either a positive or negative buoyancy force. The greater the theimal
difference and the height
of the structure, the greater the buoyancy force, and thus the stack effect.
The stack effect is also
referred to as the "chimney effect", and it helps drive natural ventilation
and infiltration.
Since buildings are not totally sealed (at the very minimum, there is always a
ground level
entrance), the stack effect will cause air infiltration. During the heating
season, the warmer
indoor air rises up through the building and escapes at the top either through
open windows,
ventilation openings, or unintentional holes in ceilings, like ceiling fans
and recessed lights. The
rising warm air reduces the pressure in the base of the building, drawing cold
air in through
either open doors, windows, or other openings and leakage. During the cooling
season, the stack
effect is reversed, but is typically weaker due to lower temperature
differences.
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Generally, a house is heated in cold climates by way of a furnace, a wood
burning stove, or the
like, in which a combustible product, such as, for example, natural gas, oil
or wood/coal is
combusted in a combustion chamber and the heat produced is moved throughout
the house in
a number of different ways. The combustion byproducts escape from the
combustion chamber
and outside of the home by way of an exhaust pipe connected to a flue or a
chimney or the like.
The tendency of the warmer house air to rise results in air pressure
differences at various levels
in the house. The stack effect in a house can make a considerable difference
in the venting and
performance of combustion appliances, such as a furnace or water heater.
Prior art methods and devices have been developed to address this issue.
United States Patent No. 4,633,768, issued January 6, 1987 (Benson) discloses
a device that
comprises a supplemental ventilation apparatus. In one of the embodiments, the
invention
discloses the ventilation system for a gas burner furnace comprising the
conventional central
flue for combustion gases release and an inlet air tube which introduces
outside air into the
furnace.
Canadian Patent No. 1,175,721, issued October 10, 1984 (Newell) discloses a
method for
increasing the efficiency of a heating system that comprises a furnace, an
exhaust pipe to
remove the combustion gases extending from the combustion chamber of the
furnace to the
exterior of the building and an auxiliary duct intersecting the exhaust pipe
to permit air to flow
from the interior of the building to the exhaust pipe. The flow through the
auxiliary duct is
controlled in part by a damper and additionally, shut-off valves.
United States Patent No. 4,920,866, issued May 1, 1990 (Hoban) discloses an
improved
combustion arrangement meant to prevent the back draft in a flue due to the
negative pressure
in the house. The invention deals with the back draft by adding an additional
duct connected to
the flue through a nozzle arranged to inject air into the flue in forward
direction. Before being
injected into the flue, the air is heated and then forced into the flue by a
fan.
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Canadian Patent No. 681,043, issued February 25, 1964 (Field) discloses a
furnace system
utilizing separate flue pipes for introducing combustion air and exhausting
smoke at the exterior
of a building. Field also discloses a cap structure for used at the exterior
ends of the flue pipes.
United States Patent No. 4,262,608, issued April 21, 1981 (Jackson) discloses
an assembly of
powered exhaust flue and preheated combustion air supply for use in
association with a heating
furnace so that the flue gases are exhausted to the outside while a balanced
combustion air
supply is pulled inside. The exhaust pipe is concentrically positioned within
the outside air
intake pipe. Both the exhaust and the air intake pipes are controlled by
dampers. The flow of
exhaust gases and fresh intake air is controlled by means of fans installed
inside the two pipes.
Canadian Patent Application No. 2,708,756, published June 30, 2010 (Melanson)
discloses a
method for equalizing air pressures within a house, the method comprising the
steps of affixing
an auxiliary air supply means to an existing exhaust stack of an existing
combustion device
located in an area with an air pressure that is lower than an atmospheric air
pressure and
supplying the auxiliary air supply means with air via an aperture located in
an area with an air
pressure that is equal or higher than the atmospheric air pressure.
SUMMARY OF THE INVENTION
The present invention provides a method of reducing the effects of the stack
effect in a house
with or without a combustion applicance. The present invention also provides
kit to perform the
method.
As an aspect of the present invention, there is provided a method for reducing
the effects of the
stack effect in a house without a combustion appliance, the house having an
attic space and a
lower portion, the method comprising the steps of: creating a substantially
air tight space in the
lower portion of the house by sealing at least one of cracks, leaks and
openings in the lower
portion of house; improving airflow in the attic space of the house by at
least one of installing
soffits around the roof line, increasing a total number of soffits, and
cleaning/clearing debris
blocking airflow through pre-existing soffits; and creating at least one
airflow path, direct or
indirect, from the lower portion of the house to the attic space.
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As another aspect of the present invention, there is provided a method for
reducing the effects
of the stack effect in a house with a combustion appliance, the house having
an attic space, a
lower portion, and a chimney stack, the method comprising the steps of:
creating a substantially
air tight space in the lower portion of the house by sealing at least one of
cracks, leaks and
openings in the lower portion of house; improving airflow in the attic space
of the house by at
least one of installing soffits around the roof line, increasing a total
number of soffits, and
cleaning/clearing debris blocking airflow through pre-existing soffits;
creating at least one
airflow path, direct or indirect, from the lower portion of the house to the
attic space; and
creating a combustion airflow path between the chimney stack and the attic
space.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will be further described, by way of
example, with
reference to the accompanying drawings, in which:
Figure 1 depicts a house having a combustion appliance, a chimney stack, and
having air
leakage;
Figure 2 depicts the house of Figure 1 having modifications according to an
embodiment of the
present invention;
Figures 3a and 3b are perspective views of a standard natural gas fueled
furnace and water
heater tank;
Figure 4 depicts a house affected by the stack effect; and
Figure 5 depicts a house using the method and/or kit according to an
embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A better understanding of the present invention and its objccts and advantages
will become
apparent to those skilled in this art from the following detailed description,
wherein there is
described only the preferred embodiment of the invention, simply by way of
illustration of the
best mode contemplated for carrying out the invention.
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An aspect of the present invention is purposed to reduce or possibly eliminate
the phenomenon
known as the stack effect, and approach equalizing air pressure in a house or
building with or
without a combustion appliance.
Figure 1 depicts a house (10) having an attic space (11) and a lower portion
(12), the lower
portion (12) being any portion of the house (10) below the attic space (11),
including all levels
of a multi-story house and may include the basement. The house (10) also has a
combustion
appliance (13) and a chimney stack (14). The combustion appliance (13) may be
installed at any
level or location in the lower portion (12).
An optional first step according to an embodiment of the invention is to
attempt to make the
interior of the lower portion (12) of the building an air tight space. For
example, this would
include sealing all cracks, leaks and/or openings (15) in the lower portion of
house (12), for
example, cracks in the foundation in and around the basement, floor joists,
doors, windows, etc.
Additionally, for further sealing of cracks and leaks and/or openings (15),
weather stripping,
caulking, foam insulation or the like may be applied.
According to another embodiment, a further step in the method of the present
invention is to
improve airflow in the attic space (11) of the house. Airflow may be improved
by installing
soffits (16) around the roof line, increasing the total number of soffits
(16), and/or
cleaning/clearing debris that may be blocking airflow through pre-existing
soffits (16).
Additionally, airflow may be further improved by installing at least one roof
vent (17) or
replacing an existing roof vent (17) with a larger roof vent. Alternatively or
in conjunction with
roof vents (17), airflow may be improved by installing one or more stack vents
(18) in the roof.
The one or more stack vents should be fitted with a rain cap (19). Preferably,
the one or more
vent stacks (18) are six inches in diameter and four feet long. The number of
soffits (16), roof
vents (17) and/or stack vents (18) that need to be installed is dependent upon
a number of
factors, such as the size of the attic space (11), and can be determined when
the air pressure of
the attic space (11) is approaching equivalency with the external pressure.
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The result of carrying out the previous steps somewhat normalizes air pressure
in the attic space
(11) with the external air pressure, which may typically provide a negative
pressure zone in the
attic space (11).
According to an embodiment, an additional step in the method of the present
invention is to
create at least one airflow path (20), direct or indirect, from the lower
portion of the house (12)
to the attic space (11). The airflow path (20) may be a hole, a vent stack, a
vent or the like, that
enables the air of the attic space (11) to communicate with the lower portion
of the house (12).
If the lower portion of the house (12) comprises multiple floors, then it is
contemplated that at
least one airflow path (20) could be installed between floors. The number of
required airflow
paths (20) will vary, and is dependent upon, inter alia, the square footage of
the building.
Location of the at least one airflow path (20) within the building can be
strategically selected
in order to maximize efficiency of pressure equalization.
When pressure differences exist between the attic space (11) and the lower
portion of the house
(12), the airflow path (20) allows for an exchange of air that serves to
equalize the pressures.
Ultimately, the air pressure inside the house (10) will approach or equal the
air pressure outside
the house (10), thereby minimizing or eliminating the stack effect in a house
(10) that does not
have a combustion appliance installed.
According to a further embodiment, an additional step of the method includes
creating a
combustion airflow path (21) between the chimney stack (14) and the attic
space (11). The
combustion airflow path (21) may be a hole in the chimney stack (14) at a
point located in the
attic space (11), installing a "T" junction in the chimney stack (14) in the
attic space (11), or
some other method known to one skilled in the art, which allows the attic
space (11) to
communicate with the chimney stack (14).
Introducing the combustion airflow path (21) reduces and/or eliminates the
stack effect in the
house (10), and in particular, within the combustion appliance, thereby
contributing to increased
combustion of fuel within the combustion appliance.
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Figure 2 depicts the house (10) of Figure 1 having implemented the method of
the present
invention, where it exhibits many of the modifications as outlined to reduce
and/or eliminate
the stack effect.
A kit is also provided for performing the method as described herein. The kit
may broadly
comprise adequate soffits, vents, roof vents, rain caps, and/or ducts. At
least some relevant
construction materials as would be understood by one of skill in the art, such
as tools, fasteners
(nails, screws etc.), may also be included in the kit.
Another embodiment of the present invention will now be described.
Figures 3a and 3b show a standard natural gas fueled furnace (1) and water
heater tank (2).
Typically, a furnace (I ) has a return register (3), a supply register (4), a
gas supply line (5), an
exhaust stack (6), and a secondary air flow (7). The gas supply line (5)
provides fuel for the
furnace (1), the fuel combusts in the combustion chamber (not shown) of the
furnace (1) and
heats the air in a heat exchanger (not shown) that is sucked in from the
return register (3), the
heated air is then blown out of the supply register to provide heat to rest of
the house.
Combustion by products, such as, for example, carbon monoxide, escape from the
combustion
chamber via the exhaust stack (6).
Similarly, a water heater tank (2) has a cold water inlet (8), a hot water
outlet (9), a gas supply
line (5), an exhaust stack (6), and a secondary air flow (7). The gas supply
line (5) provides fuel
for the water heater tank (2), the fuel combusts and heats the water in the
water tank (3), the
heated water is then available to be used throughout the house. Combustion by
products escapes
via the exhaust stack (6).
Now referring to Figures 4 and 5. The exhaust stack (6) is connected to a
chimney stack (14)
which allows combustion byproducts from the furnace (1) or water heater tank
(2) to be released
through an exterior wall and out of the house. Generally, combustion in the
furnace (1) or water
heater tank (2) is sufficient to generate an updraft through the chimney stack
(14) so that the
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combustion gases are drawn away from the furnace (1) or water heater tank (2)
to sustain
combustion and to ensure that no combustion byproducts remain in the house.
Figure 4 depicts a house (22) having a combustion appliance (13) that is
affected by the stack
effect. The arrows denote warm inside air rising in the house (22) and the
pressure gauges
denote relative air pressures in the house (22) and outside the house (22), a
clockwise movement
of the needle represents a higher relative air pressure and a counter-
clockwise movement of the
needle represents a lower relative air pressure. As can be seen in figure 4
the upper area of the
house (22) has a relative air pressure that is higher than the outside
atmospheric pressure and
the lower area of the house (22) has a relative air pressure that is lower
than the outside
atmospheric pressure. At a point between the higher air pressure and the lower
air pressure the
air pressure inside the house (22) is equal to the outside atmospheric air
pressure, i.e. the neutral
pressure plane.
Figure 5 depicts a house (23) having a combustion appliance (13) that is using
the method
and/or kit according to the present invention to reduce the stack effect. As
can be seen in figure
5, the air from areas of higher relative pressure (above the neutral pressure
plane) is being drawn
down into the auxiliary air supply means (24) via an aperture (25) into the
areas of lower
relative pressure (below the neutral pressure plane). Accordingly, if the air
is drawn from upper
areas of the house (23), the air pressure in the upper areas of the house (23)
is lowered and the
air pressure in the lower areas of the house (23) is increased, thus the air
pressures in the house
(23) are more closely equalized to that of the outside atmospheric pressure
and the stack effect
is reduced. If the air is drawn from outside the house (23), the air pressure
in the lower areas of
the house (23) is increased, thus the air pressures in the house (23) are more
closely equalized
and the stack effect is reduced.
The method according to the present invention provides for an auxiliary air
supply located
inside the house and/or outside the house to reduce the effects of the air
pressure variation, i.e.
the stack effect, and prevent back drafting. The method broadly comprises the
steps of 1)
affixing an auxiliary air supply means (24) to an existing exhaust stack (6)
of an existing
combustion device located in an area of lower relative air pressure (below the
neutral pressure
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plane), 2) supplying the auxiliary air supply means with air from an aperture
(25) located in an
area of higher relative air pressure (above the neutral pressure plane). Since
air located in a
higher relative air pressure area will flow freely to an area of lower
relative air pressure this will
create an escape for the air in the higher relative air pressure are and
balance the two different
air pressures.
The method according to the present invention may further comprise the step of
controlling the
air flow through the auxiliary air supply by way of a damping means. This
ensures that the air
can only flow out of the house in one direction and not into the house.
An embodiment of the present invention was installed and tested in a house.
Two 6" aluminum
round ducts were connected to the exhaust pipes of a furnace and a water
heater tank and sealed
with aluminum duct tape, the two aluminum round ducts are connected together
with a 6"
aluminum T round duct, the duct was then ran through the house to the uppers
levels of the
house and into the attic. In general, the attic of a house is vented to the
outside and thus will
have the same air pressure. The duct was held in place in the ceiling with a
duct thimble.
Temperature tests were conducted at various spots on the duct. The outside air
temperature was
at -15 C. At a point 18" below the ceiling the temperature was measured to be -
12 C and at the
point where the auxiliary air supply is affixed to the exhaust pipe the
temperature was measure
to be -0.2 C. This means that the cold air flowing down the auxiliary air
supply is warmed up
approximately 15 C before it reached the connection point. This shows that air
is indeed being
drawn down into the lower air pressure areas and is equalizing the air
pressure in the house as
a result of the fresh air originating from the attic.
A kit is also provided for performing the method as described herein. The kit
may broadly
comprise adequate duct to reach from an existing exhaust stack to a desired
area of higher air
pressure, duct tape for sealing the duct, duct insulation, flexible duct, a
duct thimble, a vent or
a directional vent, and a damper.
Optionally the air that is flowing from the area of higher relative air
pressure to the area of lower
relative air pressure may be outputted into the area of lower relative air
pressure. Optionally the
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air that is flowing from the area of higher relative air pressure to the area
of lower relative air
pressure may be vented outside the house via the exhaust stack (6), the
chimney stack (14) or
outside the house directly.
