Masonry Design | 47
and water leakage resistance. As an
example, the USACE standards required to
design to ASHRAE 189.1 rather than 90.1 which
not only required inspection and commissioning
of the building but set forth requirements for air
leakage that really inspired efforts to improve air
and water barriers and allowed contractors to
build better buildings knowing that the building’s
performance would be tested. We learned as
an industry how to install air and water barriers
better and the magnitude of energy savings when
we focused more on air and water barriers. The
success led to tightening the requirements of the
standard by 50%.
As extreme weather puts the spotlight on
durability, manufacturers are developing air and
water barriers that can withstand long exposure
to UV light and adhere faster in a wet
environment. Manufacturers are also looking
at new ways to apply chemistries. We’re seeing
more acrylics changing to silicones or Silyl
Terminated Polymers (STPs), and asphaltic
materials though they have a long history of
strong performance, are losing some of their
popularity due to concerns about fire and
compatibility. The tight labor market is driving
companies to develop air and water barriers that
do not require the same level of expertise and
knowledge to install compared to earlier
products. And of course, innovations that can
keep products affordable without compromising
performance are always a priority for the industry.
MASONRY DESIGN: How have air and water
barriers been integrated into LEED?
Tiffany Coppock: As an actual building code
requirement, air and water barriers were
relatively new a decade ago and initially, LEED
did not require air and water barriers based on
the ASHRAE version referenced but you could
use air barriers to possibly achieve points for
building commissioning or energy efficiency.
Since then, much attention has focused on air
filtration and removing VOCs to support indoor
air quality and there have been two versions of
air and water barrier requirements for LEED.
ASHRAE now requires an air and water
barrier be included in the design of buildings.
We’re seeing a more holistic approach to building
commissioning and various tests such as
blower door testing to assess air leakage and
whole building testing after the building is
complete.
Because air and water barriers help manage the
flow of air and vapor into and out of the building,
we can better support the building’s mechanical
performance, such as specifying properly sized
and more efficient air handler units. Collectively,
these improvements allow the building to
consume less energy, whether electricity, solar or
wind.
MASONRY DESIGN: Occupant wellness is a
growing subject of interest. How do air, vapor,
and water barriers help protect against
contaminants such as mold in the enclosure?
Tiffany Coppock: Keeping the building
environment dry and ensuring the building has
the ability to “dry out” following exposure to any
moisture is critical. While vapor barriers are not a
holistic solution to protecting against mold, they
are one tool in the toolkit. Prior to the
development of air barriers, there were weather
barriers designed to prevent liquid water leakage
above grade and waterproofing barriers to help
manage below grade moisture where
hydrostatic pressure was present. The
introduction of air barriers restricted the
movement of air and liquid moisture throughout
the building, but not necessarily the flow of vapor.
Today, there are products that stop air, liquid, and
vapor and they can be installed in one location
within the wall or in multiple locations- i.e. the air,
water and vapor barrier may be a single
membrane on the exterior sheathing or an air and
water barrier may be installed on the sheathing
and the vapor barrier is a separate product
installed on the interior behind the gypsum
drywall.
The location of the vapor barrier in the building
is very important and relates to the physics of
moisture and condensation in the enclosure. In a
hot, humid environment, moisture driven into the
building can create condensation on the interior
wall as the temperature of the living space drops
and support conditions favorable to mold. A vapor
barrier positioned on the outside of the building