Lesser-Known Code Provisions That Can Have A Big Impact on the Performance of Building Enclosures

34 • IIBEC Interface June 2021
Building enclosure consultants
are always seeking design and
construction practices that
improve the performance of
building enclosures. In my practice,
I have found that a few
lesser-known code provisions can be of great
benefit to the building enclosure. These code
provisions are related to fluid-applied flashing
in rough openings, window installation sealant
joints on the interior, and thoroughly insulated
slab-on-ground footings. In addition to
familiarizing yourself with the code provisions,
being a member of the International Code
Council (ICC) has its benefits as well. When
code questions come up, being a member of the
ICC entitles you to prompt support and clarification
of code language.
FLUID-APPLIED FLASHING
Use of fluid-applied flashing in rough openings
is not a new technology. The American
Architectural Manufacturers Association
(AAMA) first issued their “Voluntary
Specification for Liquid Applied Flashing
Used to Create a Water-Resistive Seal around
Exterior Wall Openings in Buildings” in 2011
(AAMA 714). IIBEC members were introduced
to the topic in the April 2013 issue of Interface,
which previewed the widespread commercialization
of fluid-applied flashing in the article,
“Genesis of a Waterproof Flashing System for a
Damp Climate.” By the February 2015 issue of
Interface, the authors documented that “Fluidapplied
‘paint-on flashing’ chemistries have
matured and are here to stay” in the article,
“Liquid-Applied Membranes.”
In the code, fluid-applied flashing was first
recognized (and reference was made to AAMA
714) in the 2015 International Residential
Code (IRC Section R703.4). For commercial
buildings, the ICC followed suit in the 2018
International Building Code (IBC Section
1404.4).
Although the most frequently specified system
for meeting the air-barrier code requirements
is mechanically fastened commercial
building wrap, the U.S. Department of Energy
refers to it as shown in Figure 1 concerning
air-barrier performance.
Figure 1. Characterization of mechanically fastened commercial building wrap on the U.S.
Department of Energy website.
Photo by Daniel McCullough on Unsplash
June 2021 IIBEC Interface • 35
Typically, mechanically fastened commercial
building wrap projects do not use the
blower-door test option for code compliance
of air-barrier requirements. However, fluid-applied
rough-opening flashing has developed a
reputation for facilitating successful airtightness
objectives and passing the blower-door
test option for code compliance of air-leakage
requirements (Fig. 2). For code compliance, the
air leakage during testing must be less than the
maximum leakage rate.
INTERIOR AIR AND WATER SEAL
FOR WINDOW INSTALLATION
AAMA first published instructions for sealing
the back or interior portion of the window
frame to the prepared rough opening in 2008.
In manufacturers’ instructions, this approach
was first shown in commercial product instructions
in 2010. The objective of this detailing
was to ensure that if a window leaks water into
a rough opening (some would say when rather
than if), the water cannot go into the wall
assembly or into the building. Instead, it flows
onto the treated rough opening and out onto the
water-resistive drainage plane of the sheathing
or CMU wall.
The recently issued 2021 IRC requires the
use of such an interior seal in Section R703.4.1:
“Air sealing shall be installed around all window
and door openings on the interior side
of the rough opening gap.” If interior sealing
follows the same acceptance path as fluid-applied
flashing (first appearing in AAMA and
then the IRC), it may be that the interior sealing
requirement will next appear in the 2024 IBC. If
building enclosure consultants want to specify
interior sealing on an IBC project in the interim,
the ICC has issued a code opinion confirming
that a code official may use provisions of a related code to apply a code lacking
anything specific on an issue. So, a basis exists for code officials to approve the
interior seals on current commercial projects.
Exterior sealant joints are not prohibited and may be used in conjunction
with the interior sealant joint. Some use exterior sealant joints due to historic
practice, to eliminate insect habitat, to provide still-air insulation, or for aesthetic
purposes. In this context, the external joint is sometimes referred to as
“belt-and-suspenders” or a “beauty bead.”
FROST-PROTECTED SHALLOW FOUNDATION
Figure 3 shows an example of conventional construction of slab-on-grade
footings. In this construction, the vertical concrete footing connects to the horizontal
concrete slab. The bottom of the footing must be below the frost line to avoid
frost heave, which may damage the footing and the slab. In Chicago, for example, the
footing must be at least 4-ft deep. This requires excavating a deep trench, laboriously
positioning concrete reinforcing steel, and filling the trench with a significant amount
of concrete.
Figure 2. Passive House performance values and criteria for Sehome High School.
Figure 3. An example of conventional
construction of slab-on-grade footings
(left) and a frost-protected shallow
foundation (right).
Figures 4A and 4B. These figures show insulation forms
used for frost-protected shallow foundation projects.
A
B
36 • IIBEC Interface June 2021
ASCE 32, DESIGN AND CONSTRUCTION OF FROST-PROTECTED SHALLOW
FOUNDATIONS, ANALYSIS
What follows are sequential quotations from the standard. They provide a summary of its provisions. In some instances, comments are
added in [brackets].
1. “Frost-Protected Shallow Foundation (FPSF): Foundations protected from frost heave by insulating in accordance with these provisions.
Insulation is provided to retard frost penetration below the foundation and to retard heat flow from beneath the foundation,
allowing shallower footing depths to be possible with no added risk of frost damage. Use of non-frost-susceptible soils is also included
in certain applications.” [Page 2.] 2. “Insulation placed below the floor slab shall not exceed a nominal R-value of 10 (hr • ft2 • °F/Btu) (1.76 m2 • °K/W).” [Page 5. For a
multifamily project in Erie, PA, 4 in. of EPS was used. At 4.17 per inch, this would be over R-10. However, the R-10 threshold applies
only to the ASCE 32 simplified calculation on Page 5. If the standard calculation is used, the limit is R-28. See Pages 6 and 7 discussed
in item 3.] 3. “Where the R-value of the entire slab exceeds 28, follow the design procedure for unheated buildings.” [This is when using the standard
non-simplified design method for heated buildings. See Pages 6 and 7.] 4. “For climates where F100 is less than 2250°F-days (30,000°C-hr), wing insulation along the footing is not required….” [Page 7. See
also Page 17, which provides F100 data for a sampling of various cities across the U.S. “TABLE A3. Estimates of the Mean Annual
Temperature (MAT) and the Design Air-Freezing Index (F100) at Select Locations.” A complete table of U.S. counties and their corresponding
Design Air-Freezing Index (F100) is in the 2021 IRC Table R403.3(2).] 5. [Figure 5 is located on ASCE 32 Page 10. There it is difficult both to read and understand. The markup below clarifies that the J-Form
system may be used with the addition of non-frost-susceptible soil above or below the slab insulation.] “COMMENTARY” [Commentaries are available for the building codes, and they can provide clarity for ambiguous provisions. The
ASCE 32 commentary has some useful information. For complete commentary, see pages 25-28.] 1. “Much of this introduction to the commentary is devoted to some fundamental background related to frost penetration, foundation
design, and frost-protected shallow foundations (FPSF). The remainder of the commentary gives additional background information,
data, references, and explanations in accordance with the content and organization of the Standard.” [Introduction.] 2. “The FPSF also works on unheated buildings or unheated parts of a building by use of a mat of insulation to conserve geothermal heat
supplied to and stored below ground. Figure C3 illustrates the heat exchange process in an FPSF, which results in a reduced frost depth
around the building. The insulation around the foundation perimeter conserves and redirects heat loss through the slab toward the soil
below the foundation. Geothermal heat from the underlying ground also helps raise the ground temperature underneath the building
and the frost depth around the building.” [Page 26.] 3. “Historically, foundations have been protected from frost by their extension below a locally prescribed design frost depth or by erecting
them upon solid rock.” [Page 27. ASCE 32 does not define “foundation.” At times, it appears to refer to the combined footing and slab in
“slab-on-ground” as the foundation, which is contrary to common terminology. This clarifies that the footing is the foundation.] Figure 5. Slab-on-grade foundation for unheated buildings.
Figure 3 also shows an example of a
frost-protected shallow foundation. Note that
the footing is hardly more than a thickening of
the slab perimeter. The footing was created by
placing the concrete into a form constructed of
rigid foam insulation, which remains in place.
The excavation required is measured in inches
rather than feet. Much less steel, concrete, and
labor are required with the frost-protected shallow
foundation.
The building codes have provided for use
of frost-protected insulated foundations since
1995. Amazingly, almost no one in the design
and construction industry is aware of the concept,
including code officials.
Maximum energy-efficient Passive House
construction requires all footings and slabs to
be completely insulated. Trying to insulate in
a deep trench is very difficult, so the frost-protected
shallow foundation approach is used. As
a result of the growing popularity of Passive
House construction, there is a growing awareness
and acceptance of frost-protected shallow
foundations for non-Passive House projects.
Figure 4 is a photo of an insulation form
marketed for Passive House and all other
frost-protected shallow foundation projects.
The manufacturer refers to this as a J-Form
because of its shape. There are also other similar
systems on the market.
One means of satisfying the code requirements
for frost-protected shallow foundations,
and the one that has been in the code the
longest, is to comply with Standard 32 of the
American Society of Civil Engineers’ Design
and Construction of Frost-Protected Shallow
Foundations (ASCE 32).
The J-Form system satisfies the heated
buildings requirements of ASCE 32 without
a horizontal perimeter wing outboard of the
slab-on-ground foundation footings except in
the Far North of the United States (such as
Minneapolis, Minnesota), where such a wing
is required. For vacation homes that may periodically
not be heated, ASCE 32 requires that a
layer of non-frost-susceptible soil be used over
or under slab insulation that extends out from
the footing similarly to wings needed for heated
buildings in northern climates. The J-Forms
and underslab insulation with wings satisfy
both unheated and heated building requirements.
Thicknesses for the J-Forms and the
underslab insulation boards are determined by
Engineers of Record based on the calculations
set out in ASCE 32.
Paul Grahovac holds
degrees in economics
and law. He has
been active in the
construction industry
for 30 years—first
as a construction
defects trial lawyer
and later as corporate
counsel and an
expert in air-barrier
technology and panelized
wall and window
assemblies. He
has practiced medical malpractice and hospital
negligence law, and he also spent four years
as an environmental lawyer and six years in
technology development and licensing at a U.S.
Department of Energy Radioactive Waste and
Research and Development Laboratory. He is
active in ASHRAE and well known in the Passive
House community. He is employed at two related
companies, PROSOCO and Build SMART,
where his responsibilities include codes and
standards. Build SMART prefabricates Passive
House-certified wall and window assemblies and
concrete insulation forms. PROSOCO is a provider
of fluid-applied air sealing products.
Paul Grahovac,
Esq., LEED AP
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