Note: Descriptions are shown in the official language in which they were submitted.
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A MOISTURE MONITORING SYSTEM FOR BIJILDINGS
The present invention relates to a system for monitoring structures for
the presence and accumulation of moisture. It has particular application to
monitoring residential and commercial buildings for undesired water ingress.
BACKGROUND OF THE INVENTION
Advances in building requirements and technologies emphasizing
energy conservation have resulted in insulateci and sealed buildings. As a
result,
moisture related structural integrity and the indoor air quality (IAQ)
management of
these types of buildings have become a major concern. In recent years,
considerable effort has been made to improve the performance of building
envelopes. While this effort has brought about considerable improvements in
building performance, water related problems still persist.
What is crucial is having knowleclge of the severity and extent of any
water intrusion. A critical parameter is the ability of the building materials
to store
and then disperse excess moisture. When not overwhelmed, buildings can absorb
and manage a quantity of moisture. It is only vvhen moisture levels accumulate
to a
critical level over a measured period of time that issues causing moisture
related
mould and damage arise.
Early detection and location of building envelope penetration will allow
a builder or owner to identify developing problems and to carry out minor
repairs.
Homeowners, builders, and insurance companies can avoid high costs that are
incurred from extensive structural damage, health problems, insurance claims
and
potential litigation.
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Water can collect in a building envelope as a result of infiltration or
exfiltration and condensation. Rain storms and condensation can result in
small
amounts of water leaking into a limited number of locations in the wall and
roof
assemblies. The building is able to absorb and eliminate limited amounts of
moisture. This wetting and drying process is within the normal performance
parameters of the building enclosure and should not result in a threshold
alarm.
Warning of excess moisture levels shoulci be issued only when moisture
accumulates and grows in area over an extended period of time.
In assessing the moisture perforrnance of a building envelope several
important variables must be measured, assessed and combined to derive an
estimate of the risk and corrective action needed. Key parameters include
moisture
level, duration of moisture event, number of simultaneous events and surface
area
involved.
Several moisture monitoring syste:ms are described in the literature but
all share the common limitation of setting a moi',sture alarm threshold and a
relatively
small number of monitored points. This can lead to misinterpretation of the
building
envelope performance and result in unnecessary and costly opening and repair
of
otherwise well performing wall and roof assemblies.
There are several types of moisture detection sensors available for
detecting water leaks.
In United States patent 6,175,":110 (Gott) issued January 16, 2001
there is disclosed an arrangement which uses exposed conductors on a tape of a
hygroscopic material where the current across the conductors is detected to
detect
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moisture enveloping the tape.
In United States patent 6,377,181 (Kroll) issued April 23, 2002 there is
disclosed an arrangement which uses probes which are each connected to a
conductor pair communicating with a central rnonitor which issues an alarm
when
moisture above a threshold is detected.
In United States patent 6,144,209 (Raymond) issued November 7,
2000 there is provided an arrangement which describes a location method using
a
combination of specially designed insulated and detection conductors cabled
together in a form helix. This design while useful for detection and location
of water
on floor like surfaces can not be placed between the roof deck and waterproof
membrane because of the large overall dimensions and the susceptibility of the
cable design to crushing and shorting.
US Patent 4,502,044 (Farris) issued Feb 26th 1985 discloses a plurality
of sensor elements defined by side by side pairs of conductors which are
adapted to
be mounted in two walls of a building and which connect to a central control
unit.
The control unit uses a transistor which acts to detect when voltage across a
resistor
reaches a value sufficient to turn on the transistor to emit an alarm signal.
British Patent Application 2,235,535 (Stewart) published 1991
discloses a plurality of sensor elements defined by tapes 3 which are mounted
in
walls of a building and connect to a central control unit in the form of a
leak detection
US Patent 5,081,422 (Shih) issued Jan 14Ih 1992 discloses in general
a plurality of moisture sensor elements each defined by a side by side pairs
of
conductors which have a resistance characteristic which varies in relation to
a
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moisture content. Shih also discloses the use of probes which are connected to
the
wires and are driven into the material on which the wires are attached.
The present Applicants also disclose arrangements in Published PCT
Application WO/05/10837 published February 3, 2005, which corresponds to
Canadian Application 2,513,387. These arrangements use detection tapes and
probes are suited for detecting water intrusion in selected areas of a
building
structure. The disclosure of the above application of the present Applicant
may be
reviewed for further details not disclosed herein.
Also in Canadian application Serial No: 2,520,202, filed September 19,
2005, entitled "A MOISTURE DETECTION SENSOR TAPE WITH LEAK LOCATE",
is disclosed an improved tape using four conductors which allow a location
process
to be used to locate the position of the leak along the tape. The disclosure
of the
above application of the present Applicant may be reviewed for further details
not
disclosed herein.
Also in Canadian application Serial No: 2,583,006, filed February 27,
2007, entitled "A MOISTURE DETECTION SENSOR TAPE AND PROBES TO
DETERMINE SURFACE MOISTURE AND NIATERIAL MOISTURE LEVELS", is
disclosed a moisture detection sensor is used in a building structure to
detect
moisture penetration. The sensor is a flat adhesive tape of a substrate of
dielectric,
hydrophobic material. Three or four elongate, parallel, conductors are secured
to
the top surface and a protective layer of non-hygroscopic, water pervious
material is
secured over two of the conductors so that they are exposed to surface
moisture.
One or two of the conductors are covered by an insulating layer to prevent
moisture
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access. Pairs of moisture probes along the length of the tape penetrate the
insulating layer, the respective conductors and the substrate and to extend
into a
building component to which the substrate has been adhered. A diode guide
arrangement allows a monitoring unit to monitor the exposed conductors for
surface
5 moisture and the penetrated conductors for moisture in the component by
reversing
polarity of the voltage across the conductors. The disclosure of the above
application of the present applicant may be reviewed for further details not
disclosed
herein.
In published US Patent Application 2006/0092031A1 published May ,4tn
2006 and entitled Building Monitoring System by Vokey is disclosed a building
monitoring system which monitors selected zones in a building structure for
the
presence of moisture. The system uses multiple moisture detectors, each
installed
in the structure at a location to be monitored. A remote sensor unit is
associated
with each zone to be monitored and is coupled to the detectors in the
associated
zone. The sensor unit generates an alarm signal having a characteristic
uniquely
representing the sensor unit and any wet detector to pinpoint any leakage
problem.
A monitoring unit receives alarm signals from the sensor units, decodes the
alarm
signals and generates an alarm report reporting the existence and location of
any
leakage.
SUMMARY OF THE INVENTION
The present invention proposes a system whereby moisture detectors
can be integrated extensively into a building structure to monitor for water
ingress,
where the sensors are monitored for moisture levels on the surface of and
interior to
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building components such as sheathing.
According to the present invention, there is provided a method of
monitoring moisture in a building comprising:
providing a plurality of moisture! detectors, each having a detector
parameter with a range of values ranging from a dry value in the absence of
moisture and different wet values in the presence of moisture depending on the
quantity of moisture;
dividing the building into a plurality of zones;
providing a plurality of sensor units each associated with a respective
one of said zones;
locating the moisture detectors such that each zone contains at least
one of the moisture detectors;
connecting each sensor unit to said at least one of the moisture
detector in the respective zone;
providing a common monitoring unit for cooperation with a plurality of
the sensor units;
causing the common monitoring unit to periodically poll each of the
sensor units to obtain the value of the detector parameter of said at least
one
moisture detector connected thereto;
and performing a risk assessment calculation of potential damage for
at least a part of the building using the values from the moisture detectors
for the
zones in said at least a part;
wherein the risk assessment calculation is calculated using the
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following formula:
m n
REL= ~n E TLRk() (1)
k=1 i=1
where REL is the potential average accumulated over all zones in an
elevation, m is the number days, n is the total number of zones in the
evaluation,
and LRk(i), which is derived from building science modeling for mold and/or
timber
decay fungi growth, is the potential for the growth of mold and/or timber
decay fungi
on the ith day in the kth zone as a function of the average moisture content
obtained
from the values of the moisture detectors and temperature during the day.
Preferably the building is divided into a plurality of separate parts to be
included in a separate risk assessment calculation and wherein each part
includes a
plurality of zones each having a plurality of moisture detectors.
The risk assessment calculation uses modeling to determine a risk
factor for growth of mold. For example the modeling may be taken from
Sedibauer,
K Krus M, Zilli, W et al 2001 Mold growth prediction by Computational
Simulation.
ASHRAE-Konferenz IAQ 201 San Francisco, or from Smith, SL and Hill ST 1982
Influence of Temperature and Water activity on Germination and Growth of
Aspergillus Restrictus and Aspergillus Versicoir Trans Br Mycol Soc 79 (3) pp
558 to
560, to which reference may be made.
Alternatively the risk assessment calculation can use modeling to
determine a risk factor for growth of timber decay fungi. For example the
modeling
may be taken from Winandy JE and Morell JJ 1992 Relationship between Incipient
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Decay, Strength and Chemical Composition of Douglas Fir Heartwood Wood Fiber
Science Vol 25 (3) pp 278 to 288 to 560, to which reference may be made.
As described in the above Canadian Application 2,513,387 and
Canadian Application 2,583,006, preferably the moisture detectors comprise a
tape
having at least two, three or four parallel spaced conductors thereon and a
plurality
of probes inserted through the conductors at spaced positions therealong. In
this
case, the moisture level calculation input into the above algorithm takes into
account
the number of probes on the tape.
Preferably the moisture level calculation used as input data for the
above algorithm uses moisture-resistance curves selected in relation to the
particular material on which the tape is applied.
In one example the tape is located at the floor plate of a wall in the
zone. Alternatively or additionally the tape may be located under penetrations
such
as a window of a wall in the zone.
In one preferred arrangement each sensor unit is operable when polled
to respond to a coded signal having a characteristic uniquely representing the
sensor unit.
Preferably the tape includes two conductors through which the probes
are inserted.
In particular the tape may include two conductors for surface moisture
and two conductors through which the probes are inserted for material
moisture.
Thus the sensor unit associated with each said zone is coupled to one
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or more of the detectors in the associated zone, the sensor unit being
operable to
respond to a coded signal having a characteristic uniquely representing the
sensor
unit.
Upon receiving said coded signal it will measure the response of the
detectors to which it is coupled and relay th4: measured response to the
central
computer receiving unit.
The currently preferred embodiments of the invention include a
monitoring circuit connecting the remote senscirs for delivering power and
actuation
signals to the sensors and delivering moisture measurement signals from the
sensor
units to the monitoring unit. It is also possible to provide wireless
communication
between the sensor units and the monitoring uriit, but an alternative sensor
powering
system would be required.
Thus the monitoring unit or a centrally located monitoring center which
receives sensor information from a plurality of monitoring units, performs a
risk
assessment calculation using the moisture level reading for each sensor zone,
the
number of sensor zones that are responding with higher than normal moisture
levels, and the number of consecutive time periods that the sensor zone has
reported high moisture levels.
This system and risk assessment method allows the identification of
the presence of critical moisture exposure at any area in the building where a
detector is located, allowing maintenance personnel to identify and ameliorate
leakage before it becomes a problem while avoiding the problem of overreaction
that
results from threshold based moisture alarm systems.
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It is preferred to configure the sensors to report so that areas of
concern are mapped out on the building plan elevations.
The detectors which are fully described in the above applications of the
present Applicants include tapes constructed with a pair of copper conductors
laid
5 parallel on a dielectric -substrate. In a dry state the detection tape
appears as an
open circuit. Water bridging the space between the conductors will produce a
conductive path between the conductors having a resistance in the order of a
few
thousand ohms or less, the detector parameter is in this case electrical
resistance,
although other parameters, particularly electrical parameters may be used
10 depending on the design of the detectors. As described in the earlier
patent
applications, the detectors may also include substrate penetrating probes for
detecting absorbed moisture in structural components. The detectors, sensor
units
and monitoring circuit are installed in the building structure at the time of
construction and remain in place for the life of the structure.
Each sensor unit is assigned to a particular building area, with the
associated detector tapes located at respective critical zones where water
problems
may occur within that area.
In the currently preferred embodiments of the system, the sensor units
are connected in series in the monitoring circuit. When polled, each senor
unit
transmits several signals representing respectively the moisture levels of the
detectors connected to the input ports. In the currently preferred
embodiments, up
to one hundred sensor units can be placed on a single monitoring circuit, thus
enabling the monitoring of a large number of zones in various building areas,
each
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with a unique digital code.
The computer-controlled monitoring unit applies a low voltage
powering DC across the monitoring circuit to energize the sensor units. The
same
circuit is used to receive the coded signals from the sensor units and to test
for
continuity and functionality of the circuit.
Once polled, a sensor unit applies a measuring voltage to the
moisture-detection conductors. The resistarice of the conductive path in each
detector connected to the sensor is measured and the value transmitted back to
the
monitoring unit. The zone code is unique and is linked to a database
preprogrammed into the monitoring unit to correlate moisture levels, the zone
codes
and the monitored zones. A risk assessment is then calculated and a report is
then
generated by the monitoring unit detailing thie exact location of any area in
the
building requiring attention.
The present invention preferably uses as detectors the moistu~e
detection tape and probes of the above mentioned patent applications. Each
tape is
connected to a sensing input of a remote zone> sensor that assigns a digitally
coded
address to the zone to be monitored. The remote zone sensor reports over a
pair of
monitoring conductors to a computer-based monitoring system. The monitoring
system energizes the monitoring conductors and checks for moisture levels at
regular intervals.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described in conjunction
with the accompanying drawings, wherein the showings are for the purposes of
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illustrating the preferred embodiment of the invention only and not for
purposes of
limiting same, in which:
Figure 1 is an illustration of the rrionitoring system as typically installed
in a building.
Figure 2 is an illustration of the functional design of the sensor unit.
Figure 3 is a diagram of the logic flow during the calculation of the REL
value for a selected building assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, tlhe overall arrangement of the subject
moisture detection system can best be seen with reference to Figure 1. The
building
installed components include the computer based building monitoring unit 1, a
plurality of sensor units 2 each having a plurality of inputs 4 for connection
to
individual moisture detectors 5, and a communication and sensor powering bus
3.
The building monitoring unit 1 is linked to the rrionitoring center 6 via the
internet 7 or
other suitable network link. At preprogrammeci intervals, the building
monitoring unit
1 polls the sensor units 2 which then initiate a measurement sequence
measuring
the individual moisture detectors 5. The sensor units 2 then transmit the
measured
value along with the input identification code back to the monitoring unit 1.
This
sequence is repeated until all the sensors ori the bus 3 have been queried.
The
measured values from the moisture detector zones are then forwarded to the
monitoring center 6. The monitoring center computer 6 calculates the REL level
and
reports the results.
Typically the building is divided iinto separate areas defined by the four
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separate elevations of the building since these are responsive to different
weather
effects.
Referring to Figure 2, the detailed operation of the sensor unit 2 is
illustrated. Individual moisture detectors 5 are connected to one of the
sensor input
ports 4. The input ports 4 are terminated on an input selector switch 10. The
control and A/D circuits 11 select the input port 4 to be tested and apply a
measuring voltage to the se(ected port. The measured analog value is converted
to
a digital value by the A/D converter 11 and forwarded to the transceiver 12.
The
transceiver relays the data to the building monitoring unit for processing and
storage.
The described communication and control between the monitoring
center, building monitoring unit and sensor units can be accomplished using
wireless networks. In particular, the communication between the building
monitoring
unit and sensor unit can be implemented using a wireless mesh network which
would provide a robust link between the units.
Referring to Figure 3, the flow chart details the double numerical
integration method used to calculate the REL value. The monitoring center
collects
the data from all the monitored detection zones in every monitored building.
The
collected data from individual buildings is processed to evaluate the REL
level. The
number of zones (n) of the building and number of days (m) to be included in
the
calculation are inputted into the initial conditions and the analysis
initiated 13.
Counter k is set to 1 by at step 15. Counter i is set to 1 at step 18.
Based on the moisture level and mold growth rate constants the LRk for the ith
. _ ~.
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detection zone is calculated 19 and added to the running summation 20.
Although
not shown, the process is then directed back to step 16 where i is tested for
a value
of n and then passed onto steps 18 to 20 until i reaches the value of n. When
i
reaches the value of n, i is reset to a value of 0 at step 17 and the process
is
directed to step 14 where k is tested for a value of m and the incremented by
a
value of 1 at step 15. These process loops continue until k=m at which time
the
REL for the building zones is calculated at step 21.
A report of the results is then generated for review. Typically the
report containing the REL is generated monthly. Typically a period over which
it is
necessary for the moisture to be present is at least 7 days bearing in mind
that the
probability of damage or the REL is low when only a single time period or a
small
number of such time periods of moisture penetration is involved.
The present arrangement provides a system for a more effective
prediction of damage to the building thus replacing the conventional mere
threshold
driven techniques of the prior art where a single penetration leads to an
alarm
condition regardless of the likelihood of actual damage occurring requiring
remedial
work to overcome the problem
Other mathematical computation methods may be used to generate a
value for REL. The method given above is a step wise numerical integration
technique.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the claims without department from such spirit
and
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scope, it is intended that all matter contained in the accompanying
specification
shall be interpreted as illustrative only and not in a limiting sense.
