Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PRESSURIZING BUILDINGS TO IMPROVE DRYING
This invention is in the field of drying building interiors that have
excessive moisture
accumulated therein, and in particular with drying building interiors with a
pressurized
flow of dry air.
;ta,exnw- :.+HACKGROUND 4vtht3KClU1 ay
It is well lrnown that excessive moisture in buildings causes considerable
problems.
Drywall and flooring absorb moisture and are readily damaged if the excessive
moisture
condition persists for any length of time. Interior elements such as
insulation, studs, and
joists can eventually be affected as well. Furthermore, mold begins to form on
the damp
building materials, and can remain in the structure even after it has dried,
causing
breathing problems for persons occupying the building.
At the extreme, such excessive moisture conditions are exemplified by a
flooded
building. United States Patent Number 6,457,258 to Cressy et al., "Drying
Assembly
and Method of Drying for a Flooded Enclosed Space", discloses an apparatus for
drying
flooded buildings that overcomes problems in the prior art. Such prior art is
said to
require stripping wall and floor coverings and using portable dryers to
circulate air to dry
out the exposed floor boards, joists and studs. The methods were slow and
allowed mold
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to form on the interior framing, which could then go unnoticed and be covered
up and
then later present a health hazard to occupants.
The solution proposed by Cressy is to introduce very hot and dry air into the
building,
indicated as being at 125 F and 5% relative humidity, in order to dry the
building very
quickly to prevent mold growth and allow an early return to occupants. In the
apparatus
of Cressy et al., outside air is heated by a furnace and the dry heated air is
blown thraagh
a dry air duct into a location in the building. An input end of an exhaust
duct is
positioned in another part of the building such that the dry air moves out of
theridryyair
duct, picks up moisture from the building and then moves into the input end of-
t-he
exhaust vent and out of the building. In Cressy the warmer exhaust air is =
directed
through a heat exchanger such that heat therefrom is transferred to the cooler
ioutsidexair
prior to heating by the fumace, thereby increasing the efficiency of the
system.
Prior art systems for drying flooded buildings also include desiccant
dehumidifiers that
use a desiccant material with a high affinity to water to absorb water from
the air, and
refrigerant dehumidifiers that condense water out of the air by cooling it. In
both of these
systems, the water must be disposed of in some manner. The water absorbed by
the
desiccant material is removed by subsequently drying the material. The water
condensed
by the refrigerant system is collected in a reservoir that must be emptied
from time to
time or piped to a disposal area. Such systems are relatively costly to
manufacture and
operate, and are relatively slow to remove moisture from the subject building.
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United States Patent Number 6,647,639 to Storrer, "Moisture Removal System",
addresses the problem of extracting water from interior portions of a
structure such as
inside walls and from hardwood floors. Storrer discloses using a blower to
blow (or draw)
dry air through a hose and manifolds that can be directed through injectors
into the
interior of walls.
Similarly, United States Patent Numbers 5,960,556 to Jansen, "Method for
Drying
Sheathing in Structures", is directed to drying walls with warm, low humidity
air. United
States Patent Numbers 5,893, 216 to Smith et al., 5,555,643 to Guasch, and
5,408,759 to -
Bass disclose systems for drying walls by directing pressurized air into the
inside,of dye i-'lxriv v= ,:
wall.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a system for drying
buildings that
overcomes problems in the prior art.
Co-pending United States Patent Application 2005/0145109 of the present
inventors
Dancy et al. discloses a controlled system for maintaining a desired humidity
level in
buildings and for drying buildings. Portable heat exchanger units comprise a
temperature
adjusting element, illustrated for example as comprising a fluid coil and a
fan drawing air
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from an inlet through the coil and out an outlet. The coil is connected by
conduits to a
fluid heater or fluid cooler such that the air passing through the coil can be
either heated
or cooled. By drawing in outside air and heating it, the relative humidity of
the air is
reduced, and the drier air is directed into the building. A vent is provided,
typically
somewhere opposite the intake, so that the drier air moves through the
building and picks
up moisture from building and carries it out through the vents.
The relative humidity of the air is an indicator of how much water the air is
holding, and
thus how much more water it can hold. The amount of water air can hold
increases with r. x
the temperature of the air, and the relative humidity thus decreases as the
temperature . t y ~x
increases. By way of illustration, in a closed room with standing water on the
floor, the ~~ a y~ k rrrc~~7~ 4 r
relative humidity of the air in the room would approach 100% (i.e. the air
would become
saturated with water) and so no more water would evaporate off the floor.
Raising the air
temp 10 C will reduce the relative humidity by 50% to a 50% relative humidity,
resulting
in a moisture gradient between the water and the air, and thus more water will
evaporate
off the floor and the relative humidity will again rise to 100%, provided no
air moves in
or out of the room.
By bringing in a dry air stream at a first location in the room and opening an
exhaust
vent, such as a window, door, at a second location in the room, air entering
at the first
location pushes the air in the room toward the second location and out the
vent. As the
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dry air moves through the room it picks up moisture and takes the moisture out
through
the vent. Over time the water will eventually evaporate and be carried out of
the room.
A heat controller can be operated to supply heat at the propcr rate to achieve
a desired
relative humidity in the air stream, and thus in the enclosed space. On a wet
day for
example if the outside air has a relative humidity of 100%, raising the
temperature of the
outside air by 20 C will reduce the relative humidity of the air stream to
25%.
Alternatively raising the temperature of the outside air by 40 C will reduce
the relative
humidity of the air stream to about 6% and provide fast drying in a flooded
building,
where damage to sensitive materials is not an issue.
The present invention provides, in a first embodiment, a method of drying a
building. ++:g.~mer
The method comprises closing substantially all openings in the building such
that air r-r5
movement out of the building is restricted; drawing air from outside the
building, heating
the outside air, and directing a stream of the heated outside air into the
building through
at least one input duct at an input pressure; measuring a building air
pressure of air inside
the building; comparing the measured building air pressure to a desired
building air
pressure that is less than the input pressure; and where the measured building
air pressure
is greater than the desired building air pressure, allowing a substantially
controlled flow
of air to exit the building at an exhaust location and controlling the flow of
air from the
building to maintain the building air pressure substantially at the desired
air pressure.
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A significant proportion of buildings that require drying due to floods or
mishaps will be
fairly poorly sealed against the elements. For example in many areas,
especially those in
warmer climates, vapor barriers are not commonly installed. Thus it is
possible to
pressurize the interior of these buildings with heated dry air using a fan
similar to a
furnace fan, or like available fan, to a level of about 0.2 to 0.5 water
column inches
{"WC) and force air through the walls and ceilings of the building. The method
also
provides improved drying of buildings that are better sealed against air
movernetoam
For example, a portable heat exchanger unit comprising a fluid coil connected
to a fluid
heater and a fan drawing air from an inlet through the coil and out an outlet
can be used
to draw in outside air, heat it to reduce the relative humidity thereof, and
direct a stream
of the.dry heated outside air into the building through an input duct at an
input+pressure of
about 0.6 - 0.7 "WC. With all openings in the building closed, such as
windows, doors,
vents, or the like, air movement out of the building is restricted to the
extent possible.
When the air stream is directed into the closed building, the building air
pressure inside
the building will rise. As the building air pressure rises, air inside the
building will seek
to flow to the lower pressure ambient air outside the building, and will thus
flow out
through cracks and the like in the walls and ceiling. The dry air picks up
moisture from
inside the building, and from inside wall areas to a certain extent as well,
and carries it
out as it exits the building.
The input pressure developed by the fan is a pressure differential between the
air exiting
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the input duct and the ambient outside air. Where the doors and windows of the
building
are open a very low pressure will develop in most buildings, depending on the
number
and location of the doors and windows. The fan will thus be drawing air in and
blowing
it out against negligible pressure. The volume of air in the air stream for
any given fan at
those conditions will be known, and the fluid heater can be adjusted to
provide the
desired temperature rise to that volume of air flow.
When drying a building by directing a heated and dried air stream through the
building
the amount of time air remains in the building will depend on the volume of
the interior
of the building. For example where the air stream has a volume of 5000 cubic
feet of air
entering the building every minute (cfin), and the building has a volume of
25;000,oubio-
feet, the air inside the building will essentially change every five minutes.
AtWsrutetaÃaFrw
air movement, the amount of moisture carried out by the air stream will depend
on.thr, ca
degree of moisture in the building, and the relative humidity of the entering
air stream.
The lower the relative humidity of the air stream, the higher the moisture
gradient
between the air inside the building and the wet building surfaces, and the
faster moisture
will be absorbed by the air. When the air is in the building, it absorbs
moisture and the
relative humidity thereof rises. The longer the air remains in the building
then, the more
moisture it will absorb, and thus the longer the air remains in the building,
the lower the
rate of moisture absorption and drying.
Basically then, for any given relative humidity of the air stream, the faster
the air moves
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through the building the faster the building will be dried. The operator thus
is typically
attempting to push the air through the building as quickly as possible, and
thus opens
such windows and doors as are available in order to reduce the pressure inside
the
building to a minimum and maximize the volume of the air stream flowing
through the
building.
With the method of the present invention however, the operator will detennine
that at a
building air pressure of 0.25 "WC, where the inside pressure will be such that
the air will
try to force its way through wall openings, the fan will only create an air
stream volume
of perhaps 3500 cfm instead of the 5000 cfm available where building air
pressure is
negligible. The operator then will start the fan with all building openings
closed. As the
air stream enters the building, the building air pressure will rise, and the
operator will
monitor the building air pressure with a manometer or the like, with a view to
attaining IM
the desired building air pressure of 0.25 "WC, and input air volume of 3500
cfin.
With the doors, windows, and whatever other openings might be present closed,
the
building air pressure will rise to an equilibrium point where the amount of
air in the air
stream will equal the amount of air leaking out of the building through door
seals,
window seals, cracks and the like. Where the building is poorly sealed, the
building air
pressure at this equilibrium point may be less than the desired building air
pressure of
0.25 "WC. In this situation the operator may choose to simply allow the air to
flow
through the building at whatever the building air pressure is at equilibrium,
and then
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adjust the heat to raise the temp of the air stream to the desired level.
Where obvious
large air leakage is occurring the operator may attempt to seal these leaks.
Alternatively the operator may increase the volume of air flowing into the
building by
adding a second fan to boost air flow through the coil, or by adding a second
portable
heat exchanger unit, or by like means such that the building air pressure
rises above the
desired pressure of 0.25 "WC.
Where the building is relatively well sealed, the building air pressure will
rise, and could
approach the input pressure developed by the fan. At that state very little
air would be
moving into the building.
In any event, when the building air pressure exceeds the desired pressure of,
in the
present example, 0.25 "WC, the operator allows a substantially controlled flow
of air to
exit the building at an exhaust location and controls the flow of air from the
building to
maintain the desired air pressure. Typically the operator will accomplish this
end by
partially opening a door or window in the building at a location opposite the
input
location where the air stream is entering the building.
The operator will adjust the heat supplied by the fluid heater to a setting
where the fluid
coil will raise the temperature of the air stream by the desired amount.
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The invention further provides the opportunity to control the direction of the
flow of air
through the building by positioning the exhaust location. For example where
one room or
area is wetter than the rest of the building the exhaust location can be
positioned such that
the wetter area is between the input location and the exhaust location. Air
flow will be
greatest between the input and output location as the air stream seeks to exit
the building
to the lower pressure outside. Interior fans will typically be provided at
locations
throughout the building to agitate the air and circulate same along the"walls
to improve
drying, however by moving the air stream directly through the wetter areas of
the
building, drying times will typically be reduced. Where there are two wetter
areas in a
building, two exhaust locations could be provided to split the air flow and
direct a portion
of the air flow through each wetter area. Similarly where a plurality of air
streams are
available, the input locations could be positioned to direct the air flow as
desired as well.
It is also contemplated that pressurizing the building interior will improve
the circulation
of air through the building by pushing air into all corners and like areas
that are
somewhat removed from the main air flow path. It is also contemplated that the
pressurized air will also push against the wet surfaces improving moisture
transfer from
the surfaces to the air.
DESCRIPTION OF THE DRAWINGS:
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While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and where:
Fig. 1 is a schematic top view of a building interior showing all openings in
#hem
building closed such that the building air pressure rises and at least some
air exits
the building interior through the building structure;
Fig. 2 is a schematic top view of the building interior of Fig. 1 showing a
windowPl
opened to allow a controlled flow of air to exit the building interior,
Fig. 3 is a schematic top view of the building interior of Fig. 1 showing a
window
and a door opened to allow a controlled flow of air to exit the building
interior
through two locations;
Fig. 4 is a schematic top view of the building interior of Fig. 1 showing a
window
and a door opened to allow a controlled flow of air to exit the building
interior
through two locations, and showing an increased amount of air being drawn into
the building interior.
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DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS:
Figs. 1- 4 schematically illustrate a method of drying an interior I of a
building 3. The
method comprises closing substantially all openings in the building, such as
windows 5
and doors 7, such that air movement out of the building is restricted, as
illustrated in Eig.movernent our
1. Outside air is drawn from outside the building 1 and heated, and a stream 9
of the
heated outside air is directed into the building 1 through an input duct 11 at
an input
pressure.
While it is contemplated that other apparatuses could be used, in the
illustrated
embodiment, the air stream 9 is conveniently provided by a portable heat
exchanger unit
13 comprising a fan and a coil heating element. The air is heated by hot fluid
circulating
through the coil from a boiler 15, or like fluid heater. As the air stream is
forced into the
building through the input duct 17 at the input pressure developed by the fan,
the air
pressure in the building interior I rises, since the windows 5 and doors 7 a
have been
closed. The input duct 17 is substantially sealed to the building 3 to prevent
escape of air.
Using a manometer or like instrument, the building air pressure of the air
inside the
building 3 is measured, and compared to a desired building air pressure that
is less than
the input pressure. Typically the input pressure will be about 0.6 - 0.7 "WC
compared to
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the air pressure outside the building 3, and the desired building air pressure
in the interior
1 of the building 3 will be about 0.25 - 0.40 "WC, creating a pressure
gradient between
the building interior 1 and the air outside of the building 3 such that air
inside the
building will seek to pass through the structure to the lower pressure outside
the building.
At least some air will flow through cracks or the like in the walls and roof,
especially in
buildings with no vapor barrier, as indicated by arrows 9A showing portions of
the air *+ na+~~
stream 9 passing through the walls of the building 3. For example, air will
enter a crack
in the interior wall surface, and flow along the inside of the wall until it
comes to a crack
or the like in the outside wall surface through which the air will flow to the
lower
pressure outside. In this way, some air circulation will be developed inside
the walls that
will help to dry the inside of the wall.
Typically in a relatively sound building affter the fan has been running for a
period of time
and equilibrium has been reached, the measured building air pressure will be
greater than
the desired building air pressure. The operator will then select an exhaust
location,
typically an available window 5 or door 7, although an exhaust could be
provided of any
kind, and a substantially controlled flow of air will be allowed to exit the
building at the
exhaust location to maintain the desired air pressure. Typically the exhaust
will be
opened a small amount, and when equilibrium is reached the building air
pressure will be
measured again. If it is still above the desired pressure, the exhaust will be
opened
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further, and this process will be repeated until the desired building air
pressure is attained,
at which time the exhaust will be fixed in place, the amount of heat supplied
to the air
stream will be adjusted to provide the desired temperature rise, and drying
will proceed.
Fig. 2 illustrates the window 5A being used to provide the exhaust.
w,~*-4 Phe-method of the invention also provides for directing
the'frtlW"'ofqft air stream 9
through the building such that the air flow is increased through wetter areas
or other
desired areas of the building interior 1 by configuring the input location of
the input duct
17 and the exhaust location such that an air flow is ereated from the input
location
through a desired area of the building to the exhaust location. For example
Fig. 2
illustrates a desirable configuration of the input duct 17 and exhaust
location at window
5A where it is desired to increase airflow through the room 19 in the building
interior 1,
such as where the room 19 may be wetter than the rest of the building interior
3. Thus a
portion of the air stream 9A will continue to exit through the structure, and
a portion 9B
will exit through the window 5A. While circulation fans, not shown, will
typically be
used in the building interior 1 to circulate air in the building against the
walls, air flow
through the room 19 will be greater than through the balance of the building
interior 1.
Fig. 3 illustrates a configuration where a substantially controlled flow of
air is allowed to
exit the building interior 1 at two exhaust locations, the window 5A and door
7A, such
that in addition to the air flow 9A through the structure, a first air flow 9B
is created from
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the input duct 17 through a first desired area of the building, the room 19,
to the first
exhaust location at window 5A, and a second air flow 9C is created from the
input duct
17 through a second desired area 21 of the building to the second exhaust
location at door
7A. With the door 7A opened, the window 5A will be closed somewhat compared to
its
position in Fig. 2, since it will be desired to maintain about the same area
of opening that
was provided by the window 5A alone in Fig. 2 using the window 5A
andhl2~'~flcsoi'Mtitrb
Fig. 3.
Where the building interior 3 is about equally wet throughout, the
configuration of Fig. 3
allows the room 19 to experience sufficient air flow for drying that may not
be available
without an exhaust location in the room 19. -A. 4
In some less well sealed buildings, such as older or damaged buildings, the
air stream
provided by a single portable heat exchanger unit may not be sufficient to
raise the
building air pressure to the desired level because is leaking out as fast as
it is coming in.
It may be that the operator will choose to simply let the air flow out of the
building
through the structure, or he could draw an increased volume of outside air
into the
building interior 1 by adding a second portable heat exchanger unit 13A as
illustrated in
Fig. 4 directing a second air stream 9' into the building interior through a
second input
duct 17A. The steps set out above would typically be followed to maintain the
desired
building air pressure.
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The foregoing is considered as illustrative only of the principles of the
invention.
Further, since numerous changes and modifications will readily occur to those
skilled in
the art, it is not desired to limit the invention to the exact construction
and operation
shown and described, and accordingly, all such suitable changes or
modifications in structure or operation which may be resorted to are intended
to fall within thwtawpe~Wch mav w: r-f.:ta.,nrY,K=
the claimed invention.
