Commercial Architecture February 2018 - 38
damper manufacturers may use R-values differently depending on the performance of a single component. For
example, an R-value may be promoted for the insulation
Chart 1: Leakage Classifications according to AMCA Standard 511
LEAKAGE, CFM/FT 2 (L/S/M 2 )
used in a damper blade but it does not account for the
thermal efficiency of other materials used in the blade or
Because R-value tells only part of the story, other mea-
surements have been developed by the Air Movement
and Control Association (AMCA, Arlington Heights,
EXTENDED RANGES (OPTIONAL)
IL, amca.org) to determine overall damper performance.
Two relevant AMCA standards are:
* AMCA Standard 511, Certified Ratings Program Prod-
is injected into the blade where it fills the cavity without
This is a feature to look for that further minimizes the
uct Rating Manual for Air Control Devices, details
gaps and extends down the edge. Polyurethane foam
transfer of cold or heat.
procedures for participation in the AMCA Certified
has an inherently high R-value and enables a very low
Ratings Program (CRP). Manufacturers having their
heat transfer that contributes to a high thermal efficien-
cy ratio (E).
Although the design features just described are crucial
products tested in an AMCA-accredited laboratory,
with the test results verified by the AMCA staff and
* Blade seals: A bulb blade seal is particularly effective
to improving overall thermal efficiency, it's important to
then having obtained the proper license from AMCA,
in helping block heat transfer through the blade seal.
consider some additional factors that improve damper
can offer products bearing AMCA's Certified Ratings
That's because a bulb seal creates an air pocket, which
durability and thereby ensure thermal efficiency over the
Seal for Air Leakage.
is a thermal insulator in itself. As a result, a double-in-
life of the damper.
AMCA 511 also introduces damper air leakage
classes. The maximum-allowable leakage rates defined
by AMCA are shown in Chart 1 (above).
sulation effect is created from the rubber blade material
and the air block.
To withstand more extreme environments, aluminum
damper construction transfers less heat and provides su-
* Blade jamb seals: Jamb seals should be made from sil-
perior corrosion resistance, compared with steel, thus pro-
One item to note is that air leakage, not light leak-
icone or similar durable and non-conductive material.
tecting against pitting that can compromise sealing and
age, is the critical factor. It's a common misperception
Ruskin Co. (Grandview, MO, ruskin.com), for exam-
service life. This is especially important in high-condensa-
that light leakage indicates damper blades are not tight-
ple, uses a proprietary material (Ruskiprene) that pro-
tion environments, such as pools, or high-corrosion and
ly sealed. Damper seals can eliminate a path for airflow,
tects against condensation and heat transfer better than
critical environments, such as spark-proof laboratories.
but light may still find a transmission route.
stainless steel. Stainless-steel side seals are not ideal in
For application flexibility, components can be com-
* AMCA Standard 500-D-12, Laboratory Methods of
cold-weather environments because steel readily con-
pletely customized, including:
Testing Dampers for Rating, establishes uniform labo-
ducts heat. Moreover, metallic surfaces allow conden-
* blade materials and jamb seals for corrosion resistance
ratory test methods for dampers including factors such
sate to form and travel. In contrast, Ruskiprene seals
as air leakage, pressure drop, dynamic closure, and op-
employ a fingerling pattern along the side of the blade
erational torque. It also provides methods used to cal-
to ensure tight compression. Ruskiprene and silicone
culate a damper's thermal efficiency ratio (E), which is
also have the advantage in humid applications by pre-
the amount of energy lost by conduction of heat
venting condensation from sliding through.
in a given temperature range
* additional anodized finishes for extra protection in corrosive or wet environments
* stainless-steel axles, bearings, and linkages in place of
through the damper's blades and frame. Thermal effi-
* Thermally broken blade: A thermally efficient damp-
The potential for increased energy savings makes it
ciency testing compares a complete AMCA standard
er blade requires isolation between the warm and cold
worthwhile to specify thermally efficient dampers.
reference damper assembly-including blades and jamb
sides of a damper even if the blade is insulated. Look for
However, when evaluating damper choices, be sure to
seals-with the damper being evaluated or specified. A
a thermal break that is strategically placed between
consider more than just the R-value. It's important to look
damper with the same thermal efficiency ratio (E) as
twin-blade edge seals. Twin seals create a neutral zone
at the overall damper efficiency as well as the durability
the reference damper would have an E of 0%. A damp-
that ensures there is no thermal path. These features
factors that ensure efficiency over a longer life span. CA
er that is three times as efficient as the reference damp-
eliminate thermal transfer and reduce condensation
er would have an E of 300%.
Rachel "Ray" Larimore works for Ruskin Co., Grandview,
* Thermally broken frame: Just as with blades, a ther-
MO, as a sales application engineer and has a degree in
IMPROVE THERMAL EFFICIENCY
mally broken frame isolates the high delta-T sections
nuclear engineering from the Missouri Univ. of Science
To maximize thermal efficiency, manufacturers enhance
across the damper to improve thermal performance.
and Technology, Rolla, MO.
several key damper components. In specifying a thermally efficient damper, it's imperative to evaluate the design
of the airfoil blades, the blade seals, and the jamb seals
to ensure that the assembly offers a high overall damper
Want more information?
To download the information listed below, visit commercialarchitecturemagazine.com/1802ruskin.
* Blade insulation: In thermally insulated damper
blades, the interior of an airfoil-shaped blade should be
filled with high-density polyurethane foam. The foam
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