Ways to Find Those Mystery Leaks

Analyzing water and air leakage
issues in effective and practical
ways is something with
which many building envelope
professionals have struggled.
Searching for the hidden deficiencies
in the constructed condition to find
the mystery leaks resulting in air and moisture
infiltration can sometimes stump even
the most experienced. Typically, the call
comes to the building envelope consultant
only after the owner has exhausted his or
her patience with contractors, has applied
many tubes of sealant to every visible crease
and crack, and has resigned to the fact that
scientific analysis may be required.
For many years, energy efficiency professionals
in both Canada and the U.S. have
tested building envelopes for air leakage and
performed calculations on how much natural
ventilation or air changes per hour (ACH)
are present in a building envelope. This
natural ventilation has typically been as a
result of air leakage through the building
envelope and has other uses in the energy
efficiency arena that are not applicable here.
What is very applicable, however, is
the method of detection of the air leakage
through the building envelope—either via
infiltration or exfiltration, helping us as
building envelope professionals to solve leak
diagnosis mysteries for building owners.
CREATING THE CONDITIONS
Intermittent leakage issues are usually
due to various weather-related factors coming
together to cause the problem, often a
result of wind-driven rain. The goal, therefore,
is to combine various known testing
methods to recreate the circumstance(s)
that caused the leakage to occur. One
method used to detect hidden deficiencies
in the building envelope is to create negative
air pressure conditions on the inside
of the building envelope (or a portion of
it). This reduction in the interior pressures
creates airflow through a building envelope,
imitating wind pushing against the exterior
of the building envelope. Typical induced
pressure differential to provide sufficient
airflow is over 50 Pa—theoretically equivalent
to 50-km/h (30-mph) winds hitting
the envelope from all sides simultaneously.
Once these conditions are created inside
the space, infrared cameras can be used
to look at the building envelope as a whole
and each detail and penetration. With as
little as 5°C of temperature gradient from
inside to outside temperature, it is possible
to generate very visible results of where the
building envelope is of concern and potentially
leaking.
Similar test methods involve water
spray while inducing negative pressures
typical for testing window assemblies. Water
spray testing is typically limited to warmerweather
conditions, lower elevations on
high-rise buildings, easy-access buildings,
etc. The test described in this article
requires no exterior access and requires
only a temperature differential from interior
to exterior conditions and the ability to
induce a pressure differential from the interior
to the exterior of the building envelope.
THE RELEVANCE
Why is this method of testing beneficial?
Where there is airflow that can be generated
through an exterior wall system, there is
also a path for water to infiltrate under the
right weather conditions. We have all faced
situations where we see the result of the
leak (water stains, etc.), but water testing
has proven nothing. The method of testing
discussed herein provides the building
envelope consultant with another opportunity
to discover the mystery leak and
pictorially demonstrate his or her findings
to the client.
EXAMPLES OF FINDINGS
Site #1
The first site location is of a bank
branch where the client was encountering
performance and comfort issues with the
office spaces around the perimeter of this
~465-m2 (5,000-sq.-ft.) building, suspected
to be from poor insulation and air barrier
and vapor retarder continuity. Exterior walls
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felt “drafty” from air convection. Exterior
conditions during the test were -14°C (7°F)
with no precipitation.
The test involved depressurizing the
entire building by 50 Pa, the equivalent of
a 50-km/h (30-mph) wind hitting the building’s
exterior walls and roof. Thermographic
images of the wall were taken with an
infrared camera while the building was
pressurized to identify conditions behind
the gypsum finishes. Figure 1 shows the
location in question; no evidence of interior
damage or deficiencies is visible. Figure
2 is the thermographic image of the same
column under depressurized conditions.
The darker-colored streaks outline the path
of air infiltration concentrated around the
window frame; the bright yellow
area is directly below
a forced-air heating diffuser.
Figure 3 shows a typical
exterior wall-to-floor junction
in a corner of the building.
Figure 4 identifies the same corner under
pressure, displaying significant amounts
of heat transfer due to air infiltration and
thermal bridging at the base of the walls
and surrounding the exterior steel column.
As you can see from these images, it
becomes very clear where the issues are.
As building envelope consultants, you can
effectively demonstrate to a
building owner the deficiencies.
If repair work is initiated
by the owner, this testing can be a confirmation
of the repair’s effectiveness.
These images also serve to show that an
experienced building envelope professional
could have assisted in detailing the building
design and reviewing the construction
efforts of the contractor to construct a more
efficient and reliable building.
Figure 1 – Visual image of column and window
interface at Site 1.
Figure 2 – Infared (IR) image of Figure
1. Note the streaks of dark color by
the arrow showing air leakage.
Figure 4 – IR image of Figure 3.
Dark streaks on walls and floor
indicate air leakage into building.
Figure 3 – Visual image of
wall with floor interface in
corner office at Site 1.
Site #2
Another situation tested with depressurization
of the interior environment was utilized
to detect exterior wall moisture infiltration
in a ten-story masonry-clad apartment
building. The leaks were reported to occur
when there was a driving rainstorm condition,
predominantly from easterly winds.
Detection of these leaks is nearly impossible
if not at the leak location during the rainstorm;
without the specific conditions, the
leakage will never be observed. The owner
had employed contractors for over five years
to repair exterior details, install throughwall
metal and membrane flashings, and to
install multiple layers of sealant, etc.
The test was performed on several units
located on the seventh and eighth floors.
Each individual unit was depressurized to
50 kPa (50 km/h or 30 mph) in an attempt
to identify sources of air infiltration through
the building exterior, the theory being the air
infiltration would bring the moisture with it
that was damaging the interior drywall and
flooring finishes. The test was performed
with an outside temperature of 7.5°C (45°F),
zero wind, and no precipitation.
Figure 5 shows an infrared
image of the inside face
of the exterior fenestration-
to-wall interface prior to
pressurization, showing thermal
transfer from the window
frame to the gypsum finish,
but no air infiltration. Figures
6 and 7 are images taken
during pressurization; each
image demonstrates significant
air infiltration occurring
around the windows.
After these images were
taken, a destructive test of
the window detail revealed
deficiencies in the original
construction. Termination of the air barrier
up to the window frame was allowing significant
amounts of air to enter the building,
bringing with it the moisture experienced
through driving rain.
Visual probes with a boroscope around
this window were performed, and no other
areas or evidence of moisture infiltration
could be detected within the wall cavity.
EQU IPMENT
The equipment varies from application
to application, depending on how large the
building or test area is. Generally, typical
commercial-grade blower door equipment
can be used. Segregation of areas within
a building may be required to limit air
leakage, utilizing polypropylene sheets and
tape. Additionally, a high-resolution infrared
camera that is capable of capturing
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Figure 5 – IR image of fenestration. Wall interface prior to
depressurization.
small temperature
differentials
will allow
the professional
to capture minute
deficiencies.
In the author’s
particular
case, a
Min n e a p o l i s
Blower Door
from The Energy
Conservatory
was used,
equipped with a
digital manometer
and capabilities
for multiple
fans to generate airflow volumes of up
to 14,000 cfm (~6,600 liters/second). The
authors also use a FLIR T640 thermographic
camera for this kind of testing work.
Utilization of this test procedure provides
insight to building construction deficiencies
and enables building envelope consultants
to help clients discover the sources
of many “mystery leaks.”
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Figure 7 – IR image showing significant air leakage
(streaking) between fenestration and wall system.
Figure 6 – IR image of fenestration system under
depressurization. Note streaks indicating air leakage.
Marc Schwerzmann, PEng, CEM, is a professional engineer
working with IRC Building Sciences Group Inc. He has 17
years of consulting experience and 29 years in the commercial
construction field. Much of his career has been dedicated
to retrofit work on existing building inventory with a focus
on improving building performance and energy efficiency. He
is a certified energy manager (CEM) with the Association of
Energy Engineers.
Marc Schwerzmann, PEng, CEM