An easy way to stay informed and earn PDUs
NCARB’s latest initiative to inform and educate can be found in our new “MiniMonograph” articles, which will appear in
each issue of Direct Connection. These articles will take an in-depth look at topics of
interest to architects, and provide NCARB
Record holders with an efficient and economical way to earn one or two professional
development (PDU) or continuing education
(CEU) health, safety and welfare (HSW) credits through an on-line quiz.
You’ll find our first Mini-Monograph, “The
Hidden Risk of Green Building: Avoiding
Moisture & Mold Problems,” in this issue.
After reading the article, Record holders can
earn one PDU by taking the online quiz for a
fee of $35.
To take the quiz, go to www.ncarb.org, log
onto My NCARB Record, and then click on
Mini-Monograph Quiz. You’ll be prompted to
fill out the payment information. An online
access code will be automatically e-mailed
to you, which you can use to take the quiz at
anytime. You’ll receive your results instantly,
and if you pass the quiz you can immediately
print your certificate of completion, and
NCARB will report your continuing education
credit to the AIA. Your payment covers the
cost of administering the quiz and scoring.
You even receive one free re-test should you
not pass the first time.
We hope you find our first Mini-Monograph
that follows to be informative, provocative,
and educational. If you’d like to learn more
about mold and moisture, order a copy of
NCARB’s monograph entitled, Mold and
Moisture Prevention, or one of the other 20
titles from our monographs series. A complete list of NCARB monograph titles is available on the back cover or by visiting the
NCARB web site. DC
NCARB Introduces Mini-Monographs:
THE HIDDEN RISKS
OF GREEN BUILDINGS:
AVOIDING MOISTURE & MOLD PROBLEMS
J. David Odom, ASHRAE,
Richard Scott, AIA/NCARB/LEED® AP
& George H. DuBose, CGC
Liberty Building Forensics Group, LLC
“Most new products are experiments and most experiments fail.”
Quote from “How Buildings Learn: What Happens After They’re Built”
by Stewart Brand (1994)
Stewart Brand’s caution in 1994 about using
new products is engaging and even quite controversial, since progress can only be made through
the use of new products and innovative
approaches. Yet Brand’s caution echoes what
forensic building consultants and building scientists have seen for decades; anything that departs
from the “tried and true method” often fails.
This finding is not surprising, since even traditional building materials experience some percentage of catastrophic failures from moisture
and mold problems.
Brand’s caution seems particularly appropriate
today with the proliferation of new products,
many intended for LEED (Leadership in Energy
and Environmental Design) certification.
Although many of these products have been
developed within the last five years they are
intended for use in buildings that should last for
50+ years. Even a casual review of the literature
indicates that some of these products appear to
have minimal in-situ testing or performance verification. Additionally, many of these products
have not been marketed in a manner suggesting
caution about regional or climatic restrictions in
their use. Finally, we suspect that there has been
even less testing of the complex, interrelated
assemblies in which these products will be asked
to co-exist for the next half century or more.
Yesterday’s seal of approval for new products was
“It was developed by NASA.” Today the seal of
approval is: it’s “organically produced,” LEED
certified, “earth friendly,” or some variation of
the above. Just as “NASA-developed” was no
guarantee of success, neither is LEED-certified
any assurance of no problems, especially those
problems related to moisture accumulation.
Although some indicators of a building’s performance (such as occupant comfort, energy
usage, and odors) can be ignored, you can’t easily
ignore water pouring through a wall assembly.
We don’t believe that anyone would deem a
structure “sustainable” if it cannot survive the
first five years without a major renovation
because of moisture problems.
The opinions, beliefs, and viewpoints
expressed by the authors do not necessarily
reflect the opinions, beliefs, and viewpoints of
NCARB or serve as official policy of NCARB.
After reviewing the designs of hundreds of new buildings over
the past 20 years and observing the failures in an equal number of structures the authors have found the following consistent truths:
Building Commissioning—The current industry
approach to building commissioning (even the LEED
Enhanced Commissioning version EA Credit 3) is
unlikely to prevent moisture and similar building
failures in almost any climate, except for the most
New Materials—The use of many new building products often have the unintended consequence of performing in unexpected ways, sometimes encouraging
significant moisture accumulation and mold growth.
Since wall and roof assemblies have historically been
high risk areas, it should be no surprise that the
increased use of new products in these areas can dramatically increase the overall potential of moisture problems
within the envelope.
Increased Building Ventilation—The positive benefits of
increased outside air ventilation for the occupant’s
health and comfort can oftentimes be outweighed by the
increased potential for moisture problems, some of
which have caused catastrophic failures in the past.
Forensic engineers have strong evidence that buildings
can perform in unexpected and damaging ways when
additional air is moved through them.
Through our evaluation of various LEED credit opportunities for designers, we hope to establish the fact that a sustainable building must be equally designed to prevent likely
moisture and mold problems. We believe that a building
Use the following learning objectives to focus your study while reading the semi-annual Direct Connection/ Professional Development
(PDU) and AIA Continuing Education (CU) HSW credit article. To
1. Go to the NCARB web site at
2. Click on monographs
3. Fill out the registration form and
4. Take the quiz using your online access
attaining LEED certification is not necessarily a building
with a low potential for failure due to moisture intrusion.
However, it is our belief that it is possible to combine LEED
certification with the best practices for moisture and mold
problem avoidance – but it will require extra effort from both
architects and mechanical engineers.
An important aspect to avoiding moisture problems in green
buildings is the inclusion of the best practices from the waterproofing/HVAC (heating, ventilating, and air-conditioning)
disciplines in combination with the LEED certification principles. It is unwise to assume that LEED certification has
automatically incorporated those best practices. Green building practices must always be subservient to best design practices in areas such as exterior waterproofing, good humidity
control, and proper due diligence in selecting new construction materials.
In order to facilitate the dual vision of an environmentallysensitive building with a highly durable, well performing,
moisture resistant building, we have compressed a significant
amount of data into the following discussion. This discussion
moves from an overview of LEED® certification points with
potential moisture issues (shown in a table) to a more
detailed analysis of several specific LEED credits that we view
as examples of high risk. These are credits that align with the
consistent truths we listed above concerning building commissioning, new materials, and ventilation issues.
The concerns raised in the following pages are not climatically or regionally specific, but are universal concerns for all
but the most forgiving climates. Forgiving climates would
include those areas with very low rainfall, year-round moderate temperatures, and minimal humidity levels. Even in those
climates specific building types could be expected to exhibit
problems if best practices are not followed.
After reading this article, you should be able to:
1. Comprehend how standard good practices for building design
require additional diligence due to the enhanced likelihood of
moisture intrusion connected to building commissioning protocol, ventilation, design, and novel building products.
2. Identify the specific LEED credits that increase the potential
for moisture intrusion problems during sustainable
3. Understand the contributions that good building envelope and
mechanical design play in planning a sustainable building
resistant to moisture problems.
It’s our belief that the moisture integrity of a building is one of
the best report cards on the performance of its design and construction process and the correct use of materials.
OVERVIEW OF LEED CREDITS THAT HAVE INCREASED
POTENTIAL FOR MOISTURE & MOLD PROBLEMS
The following is a summary of LEED Credits that, if not carefully considered, designed, and constructed, have the potential for creating moisture and
mold problems. This summary also includes LEED Credits that can be enhanced to minimize the potential for moisture and mold problems:
Overview of LEED Credits That Have Increased Potential for Moisture & Mold Problems
Sustainable Sites (SS)
Heat Island Effect:
Option of installing a vegetated roof for at least
50 percent of roof area.
Vegetated roofs have more moisture due to irrigation and constant hydrostatic head of water than
typical roofs, making it difficult to prevent water
intrusion and condensation problems. Moisture
migration & concentration between impermeable
membranes is a possibility.
Energy & Atmosphere
(EA) Prerequisite 1
and EA Credit 3
Commissioning of the
Enhanced commissioning addresses only the
most forgiving climates.
1. The typical commissioning design review is not
likely to predict the potential for future moisture and mold problems.
2. The reviews normally do not incorporate an
analysis of the building envelope performance.
EA Prerequisite 2 and
EA Credit 1
Increases in energy performance can reduce
moisture control in buildings.
1. Increased thermal insulation changes wall system performance (dew point location) with possible condensation in wrong location.
2. Modifying heating, ventilating, and air-conditioning (HVAC) control schemes alters equipment run times and impacts moisture control.
EA Credit 5:
Sacrificing adequate relative humidity control to
reduce energy usage.
Any good energy management plan must be
subservient to adequate moisture control.
Credits 1.1 and 1.2
Maintain 75 percent
to 95 percent of
Existing Walls, Floors,
Moisture control performance of existing building envelope components re-used under this
1. Quality and performance of existing components
such as flashing, rainwater barriers, air barriers,
need to be investigated and possibly tested.
2. Model both new and re-used component to
identify how each component will act towards
good moisture control — this includes interaction with the HVAC system.
MR Credits 1.3, 2.1,
2.2, 3.1, and 3.2
Inadvertent reuse of previously water damaged
and/or mold contaminated materials presents
an increased risk. Construction workers at risk
of handing mold contaminated materials.
1. Mold contamination is not often visible in the
occupied side of materials and is not generally
found by air testing in a construction environment. Destructive testing and evaluation may
2. Construction waste management plan may need
to include section on handling moldy materials.
MR Credit 6
Use of rapidly renewable natural building materials and products without understanding their
properties related to water (permeance, absorption, etc.).
The mixture of synthetic materials with natural
materials in the building envelope can create
increased potential for moisture condensation
EQ Credit 1, and
EQ Credit 2
Minimum Indoor Air
Outdoor Air Delivery
Ventilation in many parts of the United States
must to be carefully designed to avoid moisture
Increased ventilation air should never be added
without an overriding control of both pressurization and dehumidification.
EQ Credit 3.1
Typical construction sequencing does not always
allow for meeting credit objectives for protection
of materials from water damage.
Construction sequencing needs to be reviewed
and material protection measures understood
EQ Credit 3.2 (and
Pre-occupancy flush out.
Introducing required air for this credit in many
geographic areas can result in indoor moisture
EQ Credit 5
Indoor Chemical &
Requires significant exhaust rates for source
Local exhaust can result in local depressurization
and introduction of humid outside air into building envelope. It can also result in inadvertent pollutant movement within a building.
EQ Credit 6.2
Providing operable windows can allow untreated
humid air or rainwater to enter building.
If operable windows are installed, consider sensors and automatic overrides.
Innovation in Design
(ID) Credits 1.1-1.4
Innovation in Design
Recognizing the inherent increased risk of using
new products that have less in-field experience.
1. Probably unrealistic for the design and construction team to understand the performance characteristics and limitation of new products and
the additional risks that their use might carry.
2. Particular concern about the introduction of
new products into the highest moisture risk
areas of the building (i.e., the envelope and the
HVAC system) since in these areas there is
FUNDAMENTAL COMMISSIONING (EA PREREQUISITE 1)
AND ENHANCED COMMISSIONING (EA CREDIT 3)
Intent of EA 1: Verify that the building’s energy related systems are installed and calibrated, and perform
according to the owner’s project requirements, basis of design, and construction documents.
Intent of EA 3: Begin the commissioning process early during the design process and execute additional activities after systems performance verification is completed.
Building commissioning (even the enhanced version of commissioning in LEED EA Credit 3) is not likely to prevent catastrophic moisture and mold problems. Traditional
commissioning fails to accomplish two primary requirements
in avoiding moisture problems:
The design review is not likely to be a “standard of care”
technical peer review, but is more often a review
intended to determine if the constructed building, once
built, can be commissioned and if the design meets the
Owner’s intent. In our experience the typical design
review will not predict the potential for moisture and
mold problems. Without this prediction it cannot offer
specific solutions to avoid them.
These reviews are not required to incorporate an analysis
of the building envelope’s performance—the acknowledged component that fails the most frequently and usually the most dramatically.
What the building science industry has known for some time
is that moisture and mold problems are often very predictable, even in the early design stage. However, for this
analysis to be successful the review team must be very savvy
about what combination of design choices create a high risk
of causing problems and what other choices are lower risks.
Figure 3.1 shows an example of the predictability of moisture
and mold problems in a hotel type building.
Some concepts that should be included in building commissioning to reduce the possibility of moisture and mold problems include the following:
During the design phase a technical peer review of the
document should identify issues which will likely be
major cause of moisture and mold problems in the operating building. This review may need to be accomplished by someone other than the traditional
commissioning agent since they may not have the requisite skill set to conduct this type of analysis. It’s our
opinion that this review needs to specifically identify
which building components and systems have a high
potential for moisture problems and offer alternative
solutions to the design team.
Continuous Toilet Exhaust
FIGURE 3.1: Prediction
chart of the probability of
moisture and mold in a
hotel-type building with a
series of HVAC system
choices and an unforgiving wall system—i.e., a
misplaced vapor retarder
in conjunction with moisture sources. Other combinations of decisions can
increase or decrease the
risk. (Note: This example
makes numerous assumptions such as there are no
significant rainwater leaks.
This prediction chart also
assumes that the outside
moisture conditions are
conducive to mold
No Conditioned Make-Up Air
Conditioned Make-Up Air
Not Ducted to
Ducted to Each Room
Probable in Wall
Probable in Wall
PTAC (Packaged Terminal Air Conditioning Unit) FCU (Fan Coil Unit)
FIGURE 3.2 (left):
Qualitative water testing
of window and stud wall
assembly after installation
of membrane water
proofing. Note spray rack
(red arrows) above and
to the side of window
that washes the wall
while the cavity side of
sheathing is checked
The commissioning process needs to consider the interrelationship of the building envelope and the HVAC
system. This area is often overlooked because it involves
the dynamic interaction between two separate technology areas.
The building envelope needs to be commissioned in a
manner that would avoid rainwater leaks, excessive air
leakage, and condensation problems. In cases where the
envelope is commissioned, both individual envelope
components (like windows) should be tested as well as
assemblies of multiple adjacent components. Testing
individual components does not address the connection
points and intersections between various envelope components where most of the failures occur. Assembly testing can include a mix of qualitative (Figure 3.2) and
quantitative testing, such as ASTM tests.
Construction phase commissioning of envelope components may require adjustment of installation methods
based on test results. Checklists should be developed
that allow for certification that such adjustments are
implemented (Figure 3.3).
FIGURE 3.3 (right):
Checklists for commissioning of sliding glass
doors. These checklists
are completed by the
contractor. The checklists
may be modified after
installation and quantitative testing of the first
MATERIALS & RESOURCES AND OTHER CREDITS: USE OF
NEW MATERIALS IN HIGH RISK LOCATIONS
Intent of these 14 Materials & Resources Credits: Reuse of existing building components, the management
of construction waste, materials reuse, amount of recycled content, the use of regional materials, the use of rapidly renewable materials, and the use of certified wood.
New green materials can often meet requirements in several
LEED credits. For example, organic-based insulation materials can satisfy LEED Material & Resource Credit 6 as a rapidly renewable material, Energy & Atmosphere Prerequisite 2
and Credit 1 for energy performance, and Indoor
Environmental Quality Credit 4.1 for low emitting materials.
Many new materials and concepts can also fall under the
Innovation & Design Process credit requirements for developing new solutions, employing new technologies, or realizing exemplary performance.
We believe that it is reasonable to assume that if we are relatively unfamiliar with a new material’s individual performance then we probably know even less about the material’s
interaction with other adjacent components. Our ignorance
about the performance of new materials should not be disregarded because the manufacturer of these materials assures us
that the product is appropriate for LEED-certified buildings.
The recognition of additional risk in the use of innovative
products (especially in the envelope and HVAC systems) by
the development team should demand a higher degree of
rigor in the evaluation of these products.
As previously mentioned, the interaction between the HVAC
system and the envelope creates an unusually high risk area.
The impact of this condition is that any deficiency in either
system can cause dramatic building-wide moisture problems.
It may be only a slight overstatement to state that there is no
wall system which a creative architect can envision that a
poor HVAC system cannot destroy. Conversely, a very well
performing HVAC system can often compensate for a marginally designed (or constructed) building envelope to the
point where many moisture problems may never be noticed.
However, there is a point where even an exceptionally well
performing HVAC system cannot compensate for a poorly
designed wall system, especially a wall that allows rainwater
intrusion or is excessively leaky to air movement.
FIGURE 3.4: Example of
the amount of water
absorbed by a wall insulation product. This experiment demonstrates that
many products intended
for wall and roof assemblies can absorb huge
amounts of water in spite
of their data sheets
attesting to the opposite.
This type of evaluation may be beyond the scope and
expertise of the design team — but it should nevertheless
be implemented. In Figure 3.4 above, a new insulation
material (marketed for “green” buildings) was able to
hold a considerable amount of water despite a data sheet
that indicated it was a non-absorptive product. The use
of this material in wall cavities could create massive mold
problems if there is water leakage through the water resistive barrier since the normal wet-dry cycling will not
A simplification of the above concept can be stated as:
Bad Envelope Design + Bad HVAC Design =
Guaranteed Moisture Problems
Good Envelope Design + Bad HVAC Design =
Likely Moisture Problems
Bad Envelope Design + Good HVAC Design =
Likely Moisture Problems
Good Envelope Design + Good HVAC Design =
(Note: The term “Good Envelope Design” refers to the
correct design and construction of the air barrier, vapor
retarder, and thermal barrier. It does not refer to rainwater
intrusion issues since even minor rainwater entry past the
water resistive barrier can be problematic. “Good HVAC
Design” refers to the proper building pressurization for
the specific climate, proper dehumidification, and proper
air distribution within a building)
Although new wall system products are often intended to
provide better thermal insulation, reduce air movement
through the walls, or allow enhanced drying of the wall
assembly (via vapor diffusion) they can also perform in unanticipated ways. These new products can dramatically change
the way moisture flows through wall and roof systems and
the potential for condensation within these cavities. The use
of these new products mandate that the designer implement
several additional steps to avoid problems:
Better understand the performance characteristics of
these new products. This may require a more rigorous
evaluation of these materials than is required with traditional products. As with any product —but more so with
new products—the performance answers may not be
found in the product data sheets, but may require experiments and mockups to determine their performance.
Analyze the vapor retarder, air barrier, and bulk water
retention properties to better understand where the
material should be placed, if at all, within the wall system.
Model the wall systems for performance during the early
design stages to predict the potential for water vapor
transmission through the wall assemblies and potential for
condensation to occur. Minimally, this modeling should
predict the dew point location and the vapor transmission
profile during the most extreme season for the location.
Perform a three-dimensional analysis of rainwater barrier
geometry, especially at complex joints and changes in
All other standard good practices for wall system design
should continue to be followed whether new or traditional
products are used including:
The use of water resistive barriers as the first line of
Designing drainage planes to channel water down and
out of the envelope,
Installing secondary barriers for redundancy
Designing proper flashing and sealant joints.
INCREASED VENTILATION (EQ CREDIT 2)
Intent: Provide additional outdoor air ventilation to improve air quality for improved occupant comfort, well
being and productivity.
What is known about ventilation air is that in regions with
ambient high dew point conditions and elevated relative
humidity levels (which include much of the entire eastern half
of the country during portions of the year) there is a direct
correlation between the number of moisture problems and
increased rates of mechanical building ventilation. This can
occur for obvious reasons, such as the additional moisture load
that is introduced into the building along with the outside air.
However, more obscure reasons can also increase the risk of
adding outside air to a building. Unbalanced (or partially
depressurized) buildings can be the result of moving large
amounts of air around a building. When this condition occurs
moisture problems become more prevalent. These unbalanced
conditions happen when air is trying to flow from the supply
side of the air handler equipment to the return side but is
restricted by structural or architectural barriers.
Florida Solar Energy Center (FSEC) of Cocoa, Florida called
this condition the “Smart Air Syndrome” concept—that air is
supposed to be smart enough to get from one place to
another in spite of barriers. Additional ventilation air should
always be designed in conjunction with considering the
impact of the distribution of the ventilation air. This requires
identifying parts of the building that could become depressurized with respect to outside conditions, thus potentially
drawing humid outside air into the envelope cavity or occupied spaces. (Note: Even in less humid climates an unbalanced HVAC system can inadvertently transfer odors and
airborne pollutants in unintended ways through a building.)
This increased risk of moisture problems caused by greater air
volumes (and thus unbalanced areas of the building) is
depicted in the FSEC graphic below (Figure 3.6).
FIGURE 3.5: Martin
Stuart, Florida. The HVAC
design produced high
rates of outside air ventilation but poor temperature and humidity control
which contributed to
mold and moisture problems, resulting in over
$10 million in renovation
costs for a 3-year old
Complex Buildings + Strong HVAC Drivers = “High Risk” Buildings
Source: 1996 Florida Solar
Energy Center (FSEC)
FIGURE 3.6: FSEC
graphic on risk of building
failures related to building
complexity and intensity
of HVAC drivers (air volumes and pressures).
For decades there have been competing arguments within the
mechanical design community on whether to increase or
decrease the amount of outside air that is introduced into
commercial and institutional buildings. Although there are
sound arguments on both sides of the debate, today’s emphasis on increased building ventilation to achieve LEED credits
has given an added incentive to increase the amount of outside air to buildings. The experience of many forensic building experts (especially in the eastern half of the country) do
not necessarily support the theory that adding more outside
air creates a better performing, more sustainable building—
sometimes quite the opposite (Figure 3.5).
Source: 1996 Florida Solar
Energy Center (FSEC) Study.
FSEC’s research has demonstrated the relationship between
building complexity (architectural and structural complexity),
the intensity of the HVAC drivers (air volumes and pressures), and the risk of building failures. The solution is not to
build simpler, less ventilated buildings but it is to insure that
the ventilation air is effectively delivered to the space. This
means that ventilation must be distributed so that it not only
reaches the desired breathing zone but does so in a manner
that does not adversely affect the building.
The HVAC system that introduces ventilation air must also
do so in a manner that properly dehumidifies the air. The
“golden rule” of moisture control is that under no circumstances should adequate dehumidification be sacrificed for
increased ventilation. In many regions of the country during
summertime conditions the moisture load contributed by the
outside air can exceed the amount of moisture that the airconditioning system can effectively remove.
The solution is to address these risk factors in several ways:
Insure the correct distribution of air flows within buildings (to avoid pressure imbalances). This can usually be
accurately predicted during design.
Increase the verification of HVAC system performance
by adding additional elements to the building startup
and commissioning programs. This post-construction
verification includes detailed pressure mapping of the
building to confirm proper air distribution and using
temperature and relative humidity (RH) data-loggers to
confirm conditions during the first year’s operation. This
pressure mapping and data logging needs to also include
the building cavities—areas that are often ignored.
Many of these elements are frequently absent in today’s
standard HVAC system startup and building commissioning programs.
What experience demonstrates is that increased amounts of
outside air can be safely added to a building if the known
causes of increased risk (such as proper air distribution) are
addressed during design and verified after construction.
CONSTRUCTION IAQ MANAGEMENT PLAN DURING
CONSTRUCTION AND BEFORE OCCUPANCY
(EQ CREDITS 3.1 AND 3.2)
Intent: Reduce indoor air quality (IAQ) problems resulting from the construction/renovation process in order
to help sustain the comfort and well-being of construction workers and building occupants.
During construction there can be increased pollutant load in
a building because of various factors: heavy particulate load
and the off gassing of formaldehyde and volatile organic compounds (VOC’s) from newly installed products. There are
various methods of controlling this additional pollutant load
such as additional air filtration, the use of temporary air handlers for heating and cooling, and flushing out the building
with additional amounts of outside air.
As proposed by LEED Credit 3.2 building flush out can occur
either late in the construction phase or after the building is
occupied. While the use of outside air to flush out the building may reduce the concentration of off gassing it can also
inadvertently cause moisture problems. Although the moisture
problems may be short term (decreasing after the flush out is
finished) the resultant mold problems could be long lasting.
The EQ Credits related to the Construction IAQ
Management Plan allow for two separate approaches to building flush out, one during construction and an alternative plan
after occupancy. Both approaches involve a substantial
amount of outside air volume—14,000 cubic feet (cfm) per
square foot (SF) of floor area. Whether this flush out occurs
rapidly over a several week period (during the late stages of
construction) or more slowly over several months (during
post construction) moisture problems are likely to result in
many parts of the country during the summertime.
Increased building ventilation over the design amounts can
create a range of problems such as inadequate sizing of the air
filters and an inability of the air conditioning equipment to
handle the increased moisture (or latent) load. While the
LEED credit mandates a 60 percent RH maximum level during this flush out period this requirement may not be feasible
with the building’s equipment. Since final building finishes
should be in place prior to flush out (otherwise there are no
materials to off gas) it makes the entire building susceptible
to mold growth problems. If building flush out occurs after
occupancy then even the furnishings are susceptible to
In a typical 100,000 square foot building the amount of outdoor air required to meet the flush out portion of this credit
is 1,400,000,000 cubic feet. This amount of air volume in
the eastern portion of the country during the humid summer
months can be equivalent to over 200,000 gallons of additional moisture introduced into the building. This moisture is
in addition to the normal moisture load from construction
activities, cleaning liquids, or construction-related moisture
from curing concrete, paint drying, etc.
One of the additional risks with conducting building flush
out (especially in an occupied building) is that it is usually
done in the evening when the heat load (sensible) is the lowest and the moisture load (latent) is the highest. This can
result in even greater relative humidity levels in the building
because the unfavorable ratio of sensible to latent load can
either cause overcooling of the building (resulting in flash
condensation). The additional likelihood that the HVAC system might still be unbalanced at the time of the flush out
increases the potential for moisture problems as the result of
INDOOR CHEMICAL & POLLUTANT SOURCE
CONTROL (EQ CREDIT 5)
Depending on the climate where the building is located it
may be important to utilize different types of ventilation
approaches to control indoor air quality degradation and
indoor chemical and pollutant source control. In climates
with outdoor air conditions that carry large summer moisture
loads (which includes much of the eastern portion of the
country), ventilation approaches should include a combination of exhaust and make up air to achieve the pressure differentials required by the credit.
This credit requires a pressure differential of 5 Pascal’s (Pa)
between the area with the chemical or pollutant source and
adjacent areas. The recommended approach is to exhaust the
space with the chemical or pollutant source to a point that is
at least 5 Pa negative when compared to adjacent areas and a
minimum of .50 cfm per SF. If this recommendation is incorrectly applied its result can create depressurization of the
entire building (or portions of the building).
It increases the importance of a very accurate test and
balance process to insure that adjacent building areas are
not accidentally depressurized (including wall and ceiling cavities).
The suggested pressure differentials (5 Pa) are significantly more precise than the average test and balance
firm can measure, likely leading to errors.
Since the suggested exhaust rates and pressure differentials are minimum figures there might be a tendency for
some practitioners to vastly exceed these amounts (under
the concept that “more is better”) which could result in
an even increased potential for uncontrolled air flows
and moisture problems.
It has been the experience of many practitioners in the field
of forensic building science that achieving negative pressure
conditions in parts of a building, while maintaining overall
positive building pressures elsewhere is an extremely delicate
balance to achieve.
The inherent risks associated with increased building exhaust
as recommended in this LEED credit are numerous:
The green design movement is transforming the design and
construction marketplace like no other innovation in the lifetime of most designers. Green design has brought to the
forefront of the design and construction community a holistic
view of how to design, build, and operate higher performing
buildings. As such, the noble goals espoused by sustainable
development and green buildings are certainly worth aggressively pursuing — but it must be done with significant care,
especially in the areas of high risk for moisture and mold
problems. It seems that some of the “best practices” and
“lessons learned” in other fields are not being applied in a
precise enough manner when it involves green construction,
at least as that applies to moisture control.
To summarize our recommendations we believe that the following should occur in an effort to enhance green designs:
A technical peer review of the design should be implemented that attempts to predict the building performance with the new materials and products. At a
minimum this review would focus on the HVAC and
building envelope systems that are most exposed to
moisture-related failures. This should provide a more
climatologically and regionally accurate green design.
The design team must be confident that they have
incorporated the institutional knowledge already known
in the fields of humidity control, waterproofing and
building envelope performance. Processes that have
already lost favor in the indoor environment field, such
as “building flush out,” should not now be incorporated
into green construction as “best practices.” These
processes have historically shown little benefit and have
demonstrated high cost, high risk, or both.
The acceptance of new products with specific “green”
benefits should be especially scrutinized. Our experience
is that gaining performance in one area often means sacrificing performance in another area. If the area where
performance is sacrificed is a critical parameter (such as
the water absorption qualities of wall insulation) then
the risk may be too great, no matter what the benefit is.
We are not sure if it’s realistic for a design team to make
all of these required assessments, but without it building
failure seems more probable.
As Fortune magazine once stated:
“If mind-boggling change is the only constant, focusing on the
avoidance of major blunders yields better results than the singleminded pursuit of the big win.”
Liberty Building Forensics Group is a firm that specializes in
forensic building investigations and repairs of building failures,
moisture & mold investigations and repairs, water
intrusion/building envelope assessments and repairs, expert witness/ litigation support, and building commissioning/HVAC performance evaluations. Their staff led the investigations and
litigation support of some of the largest building failures in the
country including the $60 million moisture problems at a luxury
resort in Honolulu, HI, and the $20 million Martin County
Courthouse in Stuart, FL. They have performed technical peer
reviews on over $2 billion in new construction since 1995. They
can be reached at www.libertybuilding.com or at 407-703-1300
in Orlando, FL.
Intent: Minimize exposure of the building occupants to potentially hazardous particulates and chemical pollutants.
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