2024 Fall Online Exclusive: Mysterious Moisture Marks: Assessment of Water Stains at Window Glazing

By Patrick St. Louis, LEED;
Krishna Sai Vutukuru, PhD
This paper was presented at the 2023 IIBEC
International Convention and Trade Show.
©2024 International Institute of Building Enclosure Consultants (IIBEC)
Mysterious Moisture Marks:
Assessment of Water Stains
at Window Glazing
Online exclusive
EVERY YEAR, APPROXIMATELY 1 in every
50 homeowners in the United States claims
water damage.1 During extreme weather
events such as hurricanes and tropical
storms, the claimed damage to the interior
contents due to wind driven rain can range
from 50% to 100% of the overall damage
claims.1 Moisture intrusion is a substantial
concern because biological growth may
potentially cause structural deterioration,
serviceability disruptions, and damage to the
interior contents. Even during normal weather
conditions, condensation deposits can affect
the performance of buildings by affecting the
overall heat, air, and moisture (HAM) transfer
phenomenon and energy consumption.2 There
are also life-safety concerns. Too much moisture
within the building enclosure can lead to forms
of biological growth that are detrimental to
human health. It is critical to mitigate moisture
through proper building management that
maintains acceptable indoor air quality.
When an anxious homeowner or other
stakeholder discovers staining around windows,
a qualified building investigator can assess the
situation and provide guidance. A thorough
assessment of the reported area of staining
should include evaluations of all likely causes of
moisture intrusion.
According to the US Environmental Protection
Agency (EPA), the only way to eliminate mold
and mold spores in an indoor environment is
by controlling the moisture entering into the
building.3 Mold and other types of organic
growth are often on the surfaces of a window
assembly (“sweating”) and affects the overall
HAM of the building. Compared with the rest of
the building enclosure, openings such as these
are the most susceptible to condensation, which
transfers excessive moisture to adjacent finishes.
There are multiple building codes and
standards available for wind-driven-rain testing
during extreme weather events (Table 1).4-14
In contrast, fewer codes and standards
address moisture intrusion under normal
weather conditions.
Building enclosure issues related to moisture
can be briefly classified into three categories,
design, construction, and maintenance.
• Design-related problems may include
improper specification of insulation or
improper window design. Examples of poor
design include an exterior sill with no slope or
improperly designed drainage mechanisms.
• During the construction phase, improper
installation of an air/vapor barrier, a lack of
rain penetration tests, and improper flashing
tend to lead construction defects and potential
water and moisture intrusion.
• Inadequate maintenance and a lack of
operational awareness can lead to premature
failures and reduced life-cycle performance for
building enclosure components and systems.
Failure to perform timely inspections,
deferred maintenance, and an insufficient
preventive maintenance plan all increase
the risks for an array of water and moisture
intrusion opportunities.
WINDOW TYPES
Windows are a critical part of a building
enclosure, but they are vulnerable to age- and
weather-related damage. Because water intrusion
within a building enclosure can cause aesthetic
and structural problems, the appearance of water
stains on the interior surfaces of the window
glazing system may raise alarms for the unit
owner or building stakeholders. However, not all
water stains are the same.
Interface articles may cite trade, brand,
or product names to specify or describe
adequately materials, experimental
procedures, and/or equipment. In no
case does such identification imply
recommendation or endorsement by
the International Institute of Building
Enclosure Consultants (IIBEC).
22 • IIBEC Interface Fall 2024
Table 1. Items to consider before implementing unconventional masonry wall repair strategies
Standard Type of load Specified load Specified number
of cycles Notes
ASTM
E2834 Static 299 Pa N/A
Laboratory test
Infiltration must be less than 0.06 CFM per square foot
of glazing and 0.09 CFM/ft2 of projected window.
ASTM
E3305 Static Design wind
pressure (DP) N/A
Laboratory test
Interstory drift and deflection must be within
serviceability limits for an applied 10-sec load.
No gasket disengagement or structural failures.
ASTM
E3316 Static Largest of 20% DP
or 718 Pa N/A
Laboratory test
When a rain spray rate of 3.4 L/m².min
(5.0 U.S. gal/ft².h) is used for 15 minutes,
no water infiltration must be observed.
ASTM
E1105-05(A)7 Static Largest of 20% DP
or 718 Pa N/A
Field test
When a rain spray rate of 3.4 L/m².min
(5.0 U.S. gal/ft².h) is used for 15 minutes,
no water infiltration must be observed.
ASTM
E1105-05(B)7 Cyclic static Largest of 20% DP
or 718 Pa Minimum of 3
Field test
When a rain spray rate of 3.4 L/m².min
(5.0 U.S. gal/ft².h) is used for 15 minutes,
no water infiltration must be observed.
ASTM
E547-008 Cyclic Static 137 Pa Unspecified
Laboratory test
When a rain spray rate of 3.4 L/m².min
(5.0 U.S. gal/ft².h) is used, no water infiltration
must be observed.
BS EN
121559 Static Depends on
rating pressure N/A
Laboratory test
When a rain spray rate of 2 L/m².min is used,
no water infiltration must be observed.
BS EN
1305010 Dynamic 37.5% of design
pressure Unspecified
Laboratory test
When a rain spray rate of 2 L/m².min is used,
no water infiltration must be observed.
BS EN
1305111 Static
No loads; Annex B
suggests the use of BS
EN 12155 loadings if
air pressure is required
N/A
Field test
When a rain spray rate of 5 L/m².min is used,
no water infiltration must be observed.
BS EN
1286512 Pulsating load Incremental steps
of 150 Pa As many as needed
Laboratory test (limit of watertightness)
When a runoff rate of 1.2 L/m².min and
a driving rain rate of 1.5 L/m².min are used,
no water infiltration must be observed.
AAMA
501.1-1713 Dynamic
300.0 Pa, 380.0 Pa,
480.0 Pa, 580.0 Pa,
and 720.0 Pa
One 15-min cycle at
a time
Laboratory test/ field test
When a rain rate of 3.4 L/m².min (5.0 U.S. gal/ft².h) is
used, no water infiltration must be observed.
CSA A44014 Static 150 Pa, 200 Pa,
or 250 Pa
Four cycles of 5 min,
each with air pressure,
and 1 min with
no pressure
Field test
When uniform water film on the
outside of the window is used, no water
infiltration must be observed.
Note: N/A: Not applicable, 1 L/m2 = 0.0245 US gal/ft2; 1 Pa = 0.000145 psi; 1 CFM = 1 ft3/min = 0.028 m3/min.
ASTM: American Society for Testing and Materials, AAMA: American Architectural Manufacturers Association, BS EN: British Standards European Norm, CSA: Canadian Standards Association
Fall 2024 IIBEC Interface • 23
When evaluating water staining, it is
important to begin with an understanding of
window types and performance expectations.
Each window type discussed herein serves a
distinctive purpose, and the distinct styles and
configurations require specific approaches
toward investigation and repair.
Single-Hung Windows
Typically, a single-hung system consists of two
glass panels (sashes). Single-hung windows
open vertically, with one window panel or
sash moving up and down and the other sash
remaining stationary. Thus, when you open
the window, the upper sash is covered on
the inside. How these sections move is the
major difference between single-hung and
double-hung windows. If the operable sash
of the window is impeded from functioning
properly, that could lead to gaps and seams
that allow water intrusion. Field consultants
who perform or oversee water penetration
field-testing procedures such as ASTM E3316
should be knowledgeable at the vulnerability of
each window type. ASTM E331 diagnostic water
intrusion testing or a field modified version
(based on site conditions), delivers water via
spray nozzles near perimeter openings such as
windows and doors. This growth may be related
to poor insulation practices, which lead to a
buildup of condensation within a grid pattern,
with the water uniformly sprayed and directed
at the vulnerable areas. Within properly
installed single – hung windows, vulnerable
areas likely include exposed fasteners, gaskets,
and the operable sash. There are many other
deleterious conditions at window bases that
impede watertightness (Fig. 1).
Double-Hung Windows
Like a single-hung window, a double-hung
window has two sashes; however, in a
double-hung system, both the lower sash and
the upper sash can move up and down, and
the sashes usually tilt out for easy cleaning
and maintenance. A double-hung system has
twice the moving parts of single-hung system,
and if one or both of the operable sashes of the
window are impeded from functioning properly,
that could lead to gaps and seams to allow water
intrusion. During ASTM E 331 testing,6 water is
applied to the exterior of the test window while
the pressure inside is lowered by means of an air
chamber built on the inside or opposite side of
the test window. The vulnerable areas should be
observed. If water intrudes within the vulnerable
areas, the test can be redirected, recalibrated,
and refocused to pinpoint the source of origin.
Within properly installed double-hung widows,
vulnerable areas likely include exposed
fasteners, gaskets, and one or both of the
operable sashes.
Casement Windows
Casement windows swing out to the side or up to
open. This mode of opening allows the window
to be constructed of solid glass; therefore,
compared with a single- or double-hung window,
a casement window offers a less-obstructed view
overall. Casement windows usually come with
one casement windowpane on the left and one
on the right. Defects at any screws, bolts, springs,
or hand crank could impede the casement from
functioning properly, creating gaps and seams
that allow water intrusion.
Since casement windows operate differently
than the sliding mechanisms of other window
types, they require a slightly different verification
testing method. When preforming ASTM E3316
testing, the investigators must ensure that the
hand crank or locking mechanism is completely
engaged during the time that the calibrated
spray apparatus is applying water and uniform
static pressure is simultaneously applied to
opposite sides of the test area.
Awning Windows
Awning windows are ideal for climates with
a lot of rain because the windows create
water-resistant awnings when opened. Awning
windows swing open on the outside by being
pushed outward with the latch or handle.
This design makes awning windows more
weatherproof, but they are not invulnerable.
If an awning window is left open, updrafts
or wind-driven rain could lead to moisture
accumulation within the interior space.
Sliding Windows
Sliding windows have a minimum of two
sections or sashes, and one of the sections
slides horizontally outside/inside of the other to
open or close. Similar to double-hung windows,
if one or both operable sashes of the window
are impeded from functioning properly, that
could lead to gaps and seams that allow water
intrusion. Debris, long-term wear, or distortion
of the track may impede the window from
closing or sealing properly. Water may drain
off the base of the track during rain events or
when other water accumulates from the outside
environment. Sliding windows and other
window types may have drainage systems or
weep holes to keep water out of the window,
but the following factors can impede any water
entrapment precautions:
• Improper installation: If the window frame,
track, or base is misaligned, that can prevent
water from flowing toward or out of drains.
• Impeded drainage: Debris on the lower track
can cause obstructions.
• Lack of coordination among trades: Paint
contractors, stucco installers, or other vendors
may unintentionally apply construction
materials that cover or obstruct the weep holes.
Fixed Windows
Fixed windows include arched, picture, and
geometric-shaped windows that do not open
Figure 1. Base of sliding window was previously blocked and allowed water accumulation.
24 • IIBEC Interface Fall 2024
or close. These types of window are often
installed above standard windows that provide
ventilation. Some fixed windows can open the
same way that a casement window does. They
can also be installed in a multiarch structure
with square or rectangle windowpanes on
the side and arched curved windows. Picture
windows are fixed windows that are inoperable,
but they are often paired with operable
windows. They are large window types that do
not have any breaks or visible frames. Fixed
windows have no operable sashes, panels, or
mechanisms with no potential for gaps, seams,
or misalignments that create ideal paths for
water intrusion. Therefore, if there is water
intrusion, attention should be focused on the
condition and construction of the window frame.
The condition of the window frame material
is a significant concern during the evaluation
of water intrusion, and forensic water testing
may be warranted. Deterioration or distortion
of the window frame can be the source of the
mysterious water stains.
In window frames made wood, deterioration
from rotting or warping is a commonplace culprit
in water intrusion. Absorbed moisture causes
wood rot and creates ideal conditions for further
rot, biological growth, and pest infestation.
Termites and other wood burrowing insects can
further damage the wood and create additional
pathways for water intrusion.
When the window frame is made of untreated
wood, moisture can become trapped and
long-term cycles of expansion and contraction
can lead to permanent bends in the frame that
distort the window’s appearance, making it look
crooked, twisted, cupped, or bowed. In addition
to the aesthetic effects, such distortion can
adversely affect the window system’s operation
or weathertightness.
PERFORMANCE EXPECTATIONS
The industry standard specification for
evaluating fenestration products is AAMA/
NWWDA 101/I.S. 2-08 Voluntary Specification for
Aluminum, Vinyl and Wood Windows and Glass
Doors.22 It establishes the following performance
requirements for a window assembly:
• Structural ability to resist wind loads or wind
pressure standards
• Resistance to air leakage
• Resistance to air infiltration
• Resistance to forced entry
Products that with the certification under
AAMA/NWWDA 101/I.S. 2-08 are designated
by a four-part code that denotes the type
of window, the performance class, and
performance grade. For example, the code
C-R15 indicates a casement window (C)
recommended for residential applications (R),
with a performance grade of 15. How well a
window performs when subjected to heavy
rains and high wind pressures reflects its
performance grade and design pressure. The
window design pressure (lb/ft2) is typically
provided based on the structural rating only.
However, a strong structural assembly prevents
the risks of component displacement and
further water intrusion. In addition to this design
pressure, the performance grade indicates that
a window has met the water resistance and air
infiltration standards for that grade.
The minimum recommended design
pressure for residential windows is 15 lb/ft2
(73.24 kg/m2). A design pressure of 15 lb/ft2
means a window has been tested to withstand
sustained wind pressures of 22.5 lb/ft2
(109.85 kg/m2), roughly equivalent to a 95 mph
(42.5 m/s) wind (depending on the pressure
coefficient), applied to either side of the
window, simulating either positive or negative
wind pressures. The test pressure is always
150% of the rated design pressure to provide
a safety factor. To earn a performance grade
of 15, a window must also pass a water
pressure test of 2.86 lb/ft2 (13.96 kg/m2), which
simulates rainfall of 8 in. (203 mm) per hour
with a wind speed of 34 mph (15.2 m/s).
In coastal areas or other areas prone
to intense rain events or hurricanes,
higher-performance-grade windows
exceeding minimum code requirements are
recommended. Window design pressure ratings
combine the window’s resistance to (a) water
leaks, (b) air leaks, and (c) actual structural
loading. Points are assigned for the window’s
ability to resist each type of force and then a
total window performance grade rating number
is calculated. Higher ratings indicate better
performance in preventing common causes of
water intrusion. Thus, a high rating describes
a window that is significantly more resistant
to water and air leaks than the threshold
performance criteria.
A consideration when setting performance
expectations and investigating window
conditions will be the perimeter conditions. All
window systems, regardless of their condition
at the time of assembly, are susceptible to
the passage of time and exposure. Sealants
that are vulnerable to age can dry and crack,
leaving passageways for water to enter the
wall structural enclosure (Fig. 2). Unpainted
areas of the exterior wood window frame
components will retain moisture, potentially
subjecting the frame to accelerated rot and
decay. Over time, framework for both wood
and aluminum windows can expand and
contract with temperature changes, thus
creating space at the perimeter of the window
system where water intrusion can occur.
Fluctuations between daytime and nighttime
temperatures cause repeated movement of
window glass that expands in warm weather
and contracts in cool weather. This movement
can cause glass to fracture to allow water
intrusions. In double-paned windows, flexing
motion can cause the seals between the panes
to fail, resulting in window condensation fog.
On rare occasions, windows assemblies
have defects due to their original manufacture.
For example, newly fabricated window frame
materials may exhibit cracks or splits either at the
manufacturer or after transport to the site.
Although defects may be difficult to observe
in an installed window system (Fig. 3),
exposed defects may be noted during a
visual inspection. Outside the wall, gaps and
Figure 2. Aged sealant conditions
around a window.
Figure 3. Improper assembly at the joining of
window systems.
Fall 2024 IIBEC Interface • 25
unsealed elements might be noted in the
exposed window joinery and miter joints.
Separation and other defects tend to occur
at the 90-degree angles of the corner miter
joints. The lack of a firm seal at mull bars or
at the joining of window assemblies may also
allow water intrusions.
Water stains may occur early if windows
are improperly installed and allow water
intrusion through gaps, voids, and
separations. When evaluating window
installations, investigators should assess
whether corrosion-resistant flashing and the
watertightness methodology are sufficient
to divert water away from the building
enclosure and prevent water intrusion within
the wall cavity and frame components of the
structure. The investigator should be familiar
with the window assembly and associated
building construction and be capable of
recognizing whether fasteners are missing,
components are misaligned, or waterproofing
is improperly installed.
Recent weather history at the site is also
an important influence on the assessment.
Different types of severe weather events
can affect window components in different
ways. Hail can cause physical damage to
not just window frames and glass but also
the surrounding exterior cladding. Hail can
break glass panes, allowing water intrusion
during and after a rain event. Impact
dents from hail on the window frames may
affect the way that the window operates,
thus compromising the watertightness.
The impact of windborne debris adjacent
to window openings can also create
openings for water to intrude through the
building enclosure.
TYPES OF STAINING
Water stains on windowsills and at the
perimeter of the openings can be a source of
anxiety for building owners and occupants.
The cause of a stain might be a simple drop
or splash from watering a nearby plant,
or the stain may be the tip of the iceberg,
indicating a larger structural issue. This is
why it is so important to determine whether
stains are the sign of a major leakage
problem or not.
Water Accumulation–Clear
The appearance of standing or pooling
water around or at the base of a window is
often reported as a leak. It is important to
investigate and figure out where the moisture
is coming from. If the window is open, you
should be able to close the window, mop up
the mess, and not worry much further. But
if a closed window allows water infiltration,
that suggests faulty installation or failure
of materials. Such situations warrant
further investigation.
Stains and Discoloration–Amber
Another sign of a window leak is the
appearance of stains or discoloration. The
area could be dry or wet, and the stains may
be copper, yellow, or brown residue. Growth
of the stain over time is a likely sign of a
leak. Reddish staining can also be a sign of
corrosion of metal fasteners or structural rebar
reinforcement (Fig. 4).
Biological Growth–Green or Black
Biological growth often occurs in areas of
excess moisture such as bathrooms, kitchens,
and basements. If it appears on or around
windows in an area without any plumbing
fixtures or any obvious sources of running
water, the cause is likely a leaky window.
Biological growth can look spotty and fuzzy
(Fig. 5). In addition to being an eyesore,
airborne spores can adversely affect health
and well-being or produce musty odors.
The odor often stems from areas where
moisture has been accumulating for long
periods. Interior finishes such as drywall are
absorbent when saturated with moisture, and
as low-air-circulation environments, they can
serves as petri dishes for biological growth and
detectable odors.
Finish Distortion–Fading
When drywall absorbs water, this can cause
paint to fade and wallpaper to lose adhesion.
Therefore, if the interior finishes adjacent to
the window assembly begin to distort and
peel away from the wall surfaces, leaks in the
window assembly should be suspected. Water
intrusion through the window assembly can
also lead to fading or flaking of the window
finishes. Distortions of the window frame
such as warping will also compromise the
window integrity (Fig. 6). Walls around the
windows may also exhibit signs of significant
separation gaps as the materials warp.
Soft spots and spongy materials will sag
because of the weight of entrapped water
and as building materials deteriorate. The
buildup of biological growth, wood rot, and
pest infestation can add mass beneath the
surface. Extensive warping could be the
result of structural damage. These conditions
merit additional review and are expensive to
investigate and repair.
Figure 4. Red stains reveal compromised conduit not window assembly.
26 • IIBEC Interface Fall 2024
Window Sweating
The fundamentals of window sweating are
simple. When the air within the building
enclosure forms a convection current cycle
against the cold surfaces of a window, the
colder air sinks and warm air replaces it.
As warm, moist air encounters the colder
interior glass surface, the air drops below
dew point, depositing moisture on the
glass. As the convection current process
continues over time, additional moisture
leaves deposits on the glass. Adjacent
surfaces may eventually become stained
as built-up condensation on the surface of
glass drips onto the windowsill and other
surfaces. If an individual is not present to
witness this process, the cause of staining
may be a mystery.
When investigating “sweating” windows
and related staining, it is important to keep
in mind that condensation on windows
within an enclosed occupied space may not
necessarily be a sign of water infiltration.
Human activities such as showering, cooking,
and simply breathing can affect the dew point
and convection current cycles, leading to
condensation on glass.
Understanding the types of window glass
installed in the building enclosure is important
to assess the appearance of water and its
significance. Single-paned windows are less
energy efficient and less insulated than
their double-paned counterparts. Therefore,
the use of single-pane glass can lead to
more condensation on the window surface,
increasing the risk for water staining of the
window trims, surrounding walls, and floor
surfaces below.
Condensation can be the result of poor
thermal bridging design. Thermal insulation
acts as barrier to regulate temperature as per
the design intent. When thermal insulation
is interrupted by a window, condensation can
build up, resulting to areas of water staining
and distortion.
The window assembly material may further
affect the risk for moisture condensation
buildup and staining. High-conductivity
materials such as aluminum have low thermal
resistance relative to insulated materials, which
means they allow heat to bypass the thermal
barrier. Investigators should understand
which window materials carry higher risks that
may factor in the assessment and mitigation
strategies going forward. Guidelines such as
Voluntary Test Method for Thermal Transmittance
and Condensation Resistance of Windows, Doors
and Glazed Wall Sections (AAMA 1503-09)23 can
be used to evaluate c Figure 6. Distortion at window. ertain window elements
Figure 5. Example of bio growth.
Fall 2024 IIBEC Interface • 27
and provide expectations for condensation
resistance. The AAMA condensation-resistance
factor (CRF)23 indicates the magnitude of the
temperature-driven vapor that can take the form
of condensation. That type of condensation can
potentially mislead an observer to conclude
that the window is defective. Determining
a window’s CFR and taking note of the
surrounding environment are key to a proper
assessment of the source of water stains.
FACADE ASSESSMENT
In addition to window condensation, other
causes of moisture stains can range from
steam from a teapot to more serious causes
such as an underperforming HVAC system.
Properly maintained and balanced mechanical
ventilation systems are needed to control the
moisture levels within the enclosure. Depending
on the airtightness of a design and the
performance of operable natural ventilation, the
rate of moisture may fluctuate dramatically and
result in dew point moisture accumulation and
staining of surfaces at the window area.
With recent advancements in technology,
several noninvasive methods have been
developed to gain insight to mysterious
moisture stains near the window. These
innovative methods can be employed to
analyze a variety of construction defects, wall
coating failures, and potential structural issues
that can be hidden behind moisture stains.
An investigator’s initial observations of
the exterior facade may involve the use of
long-range binoculars or a high-power camera
lens. These tools are beneficial when you
have a direct line of sight. However, there are
times when the target area of concern is in an
obscured location and costly mobilization of
equipment would be required to gain a clear
vantage point.
Commercial unmanned aerial vehicles
(drones) can be used to avoid the need for lift
booms and scaffolding as staging equipment.
When equipped with a high-quality camera
lens, a drone may help the investigator
visually note deviations in the facade (Fig. 7).
Deleterious facade conditions may correlate
with the moisture staining, water-related
distortion, or biological growth witnessed
within the building enclosure. The photographic
survey performed by the drone can document
from a variety of angles, positions, and
heights any threats of structural failure, loss
of facade elements, and other potential issues
responsible for the water stains.
As discussed earlier, failures of installed
window sealant (or other building
components) can take the form of distortions,
Figure 7. Example use of aerial drone.
Figure 8. IR facade survey via drone.
28 • IIBEC Interface Fall 2024
voids, and displacements that allow water
intrusion and lead to interior staining.
Sealant failures may be due to insufficient
sealant adhesion, incorrect sealant cure
times, or sealant joint discontinuities. In
some cases, inconsistent quality control
measures or improper product specifications
for the sealants may be the likely cause of
water stains. Visual inspection may narrow
the universe of potential causes to sealant
issues instead of window assembly defects.
If so, the costly and unnecessary endeavor
of building permitting and purchasing and
installing window assembly replacements
can be avoided.
Not all defects are visible to the seasoned
investigator’s naked eye or via the ocular
lens of a typical drone camera. It is
therefore fortunate that not all cameras
are the same. Specialized drones with
dedicated cameras with infrared (IR)
thermography capabilities are available.
The IR thermography can capture the
temperature distribution on surfaces and
relay that information on a visual spectrum.
The drone can be maneuvered across the
facade and over large areas in the search of
abnormalities. It can also focus on specific
areas that may correlate with locations
of reported interior water staining. IR
imagery may identify discontinuities of
the building enclosure’s facade that are
not visible by standard methods (Fig. 8).
The speed of the IR assessment via drones
allows the investigator to view “invisible”
conditions within inaccessible areas in an
expedited manner, thereby preventing
future water damage. Thermal modeling
of the facade while using fixed-measure
temperatures as point of calibration can be
ideal to understand, analyze, and provide
recommendations for mitigation.
CONCLUSION
When investigating mysterious moisture
stains, an effective strategy is to determine
the logical steps of the investigation based
on facts, reasonable expectations, and
precedents based on scientific research. The
investigation should include the following:
• Identifying the physical evidence around
the window system without first making
presumptions about the source or causality of
the staining
• Gathering and documenting the visual
information from both the interior space and
the exterior environment about the window
system and adjacent conditions
• Interviewing owners, tenants, and other
stakeholders about the installation, use, and
maintenance of the window system
• Reviewing past and present information about
neighboring window systems and similar
adjacent conditions
Often, the goal of a moisture distress
assessment is to determine whether the
concerns are justified, identify the sources of
identified problems, determine the causality,
and assess any life-safety risks. After the initial
assessment and observations, investigators
should communicate their findings, risks,
and recommendations to the stakeholders.
The assessment should be used to determine
whether interior staining indicates detrimental
water intrusion or superficial surface
condensation and then form an appropriate plan
of action to mitigate and address the sources
of water stains. The action plan may involve a
systematic approach of targeted water testing
as established in AAMA 51124 or ASTM E2128.25
Test protocols vary based on specific conditions
and components. An alternative approach to
water testing involves selective demolition to
investigate the water stain areas and repair
the issues discovered. These approaches vary
in terms of costs, durations, and interruptions,
which is why it is important to conduct a
preliminary assessment before choosing what
actions to take. Poor workmanship, failure of
window systems, and simple user error require
different approaches and resolutions. Simple
reasoning can shed light to the mysterious
appearance of moisture stains and provide
proper direction. Figure 9 provides an overview
of typical moisture stain assessment by a
building investigator and future steps.
Figure 9. The path of assessment.
Fall 2024 IIBEC Interface • 29
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ABOUT THE AUTHORS
Patrick St. Louis,
LEED Green
Associate, is a senior
project director
with Thornton
Tomasetti (TT) in
the Fort Lauderdale,
Florida, office, in the
Forensic, Renewal,
and Property Loss
practice. St Louis
has been with TT
for over nine years with a primary focus
on forensic and renewal architecture. He
has his bachelor’s degree from Florida
Atlantic University.
Dr. Krishna Sai
Vutukuru, PhD, is
a senior engineer at
Thornton Tomasetti
Inc. (TT) in Fort
Lauderdale, Florida.
Vutukuru has been
with TT for one year
and specializes in
built environment
vulnerability to
extreme wind
events such as hurricanes, wind-driven rain,
downbursts, and tornadoes. He has bachelor’s
and master’s degrees in civil engineering
from the Indian Institute of Technology,
Varanasi, as well as master’s and doctorate
degrees in civil engineering from Florida
International University.
PATRICK ST. LOUIS,
LEED
KRISHNA SAI
VUTUKURU, PHD
Please address reader comments to
chamaker@iibec.org, including
“Letter to Editor” in the subject line, or
IIBEC, IIBEC Interface,
434 Fayetteville St., Suite 2400,
Raleigh, NC 27601.
30 • IIBEC Interface Fall 2024