Conference PaperPDF Available

Architectural Insulation Modules: Thermal and Structural Performance for Use in Curtainwall Construction

Authors:
  • Dow Corning Corporation, Midland Michigan USA

Abstract and Figures

Increasing pressure to upgrade curtainwall thermal performance is occurring globally. The high vision areas and aluminium framing of typical commercial curtainwalls at a thermal disadvantage compared to other construction types. This has resulted in the engineering and design of highly insulating spandrel sections of the curtainwalls to improve on the overall U value of façade while maximizing the architectural desire for large glazing areas. Architectural Insulation Modules are designed to be highly insulating spandrel sections that replace double glaze and triple glaze assemblies within the curtainwall framing. The modules contain Fumed Silica Vacuum Insulation Panels within the air space between two rigid structural panels such as glass or metal. The separation between the rigid plates is maintained with warm edge insulating glass technology that utilizes primary seals of polyisobutylene, secondary seal technology of structural silicone and moisture absorbing desiccant. Architectural finishes can be placed on the exterior or interior of the assembly to keep the design freedom associated with commercial curtainwall construction.
Content may be subject to copyright.
ICBEST 2014
June 09-12, 2014, Aachen, Germany
Architectural Insulation Modules: Thermal and Structural Performance for Use
in Curtainwall Construction
Lawrence D. Carbary1, Stanley Yee1, Nick Bagatelos2
1Dow Corning Corporation, Midland, Michigan, USA
2BISEM-USA, Sacramento, California, USA
Corresponding author: Lawrence D. Carbary l.carbary@dowcorning.com
Abstract
Increasing pressure to upgrade curtainwall thermal performance is occurring globally. The high vision
areas and aluminium framing of typical commercial curtainwalls at a thermal disadvantage compared
to other construction types. This has resulted in the engineering and design of highly insulating
spandrel sections of the curtainwalls to improve on the overall U value of façade while maximizing the
architectural desire for large glazing areas.
Architectural Insulation Modules are designed to be highly insulating spandrel sections that replace
double glaze and triple glaze assemblies within the curtainwall framing. The modules contain Fumed
Silica Vacuum Insulation Panels within the air space between two rigid structural panels such as glass
or metal. The separation between the rigid plates is maintained with warm edge insulating glass
technology that utilizes primary seals of polyisobutylene, secondary seal technology of structural
silicone and moisture absorbing desiccant. Architectural finishes can be placed on the exterior or
interior of the assembly to keep the design freedom associated with commercial curtainwall
construction.
Thermal performance of 1500mm x 1500mm modules is modelled in both two dimensional and
three dimensional models. In addition, the modelling is validated with hot box testing of the modules
according to ASTM C1363. Architectural Insulation modules 1500 mm x 1500mm x 50 mm have
been shown to achieve total U values of 0.30 (W/m2K)in hot box testing. This can then be further
modelled to be placed into curtainwall spandrel areas to achieve a total spandrel U value of 0.39
(W/m2K) including framing. A comparison is made with the 3 dimensional models of typical existing
spandrel curtainwall construction in North America, showing reductions in heat flow up to 68% are
possible using the architectural insulation modules without extreme changes in design, materials, or
engineering.
The architectural insulation modules were then placed into a full size curtainwall and tested. Air
Infiltration as tested to ASTM E283 conducted at 300 Pa positive static air pressure difference.
Static Pressure Water Resistance was tested to ASTM E331 at 720 Pa positive static air pressure
difference for a 15 minute duration. Water was applied to the mock-up at a minimum rate of 3.4 L/m2
min.
Dynamic Pressure Water Resistance was tested to AAMA 501.1 was conducted with a dynamic
pressure equivalent of 720 Pa for a 15 minute duration. Water was applied to the mock-up at a
minimum rate of 3.4 L/m2 min.
Structural Performance was tested to ASTM E 330, at positive and negative 2.4 kPa and 150%
proofload of 3.6 kPa.
Interstory Lateral and Vertical Differential Movement was tested to AAMA 501.4/ 501.7,
respectively. Three complete cycles were performed in the horizontal and vertical direction at the
floor simulation. Testing was conducted at movements up to 47mm.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 2/18
Seismic Movement was tested to AAMA 501.4-09. Testing was conducted at 89mm of interstory
drift.
The study concludes that higher performing curtainwalls can be achieved without sacrificing the
existing structural, seismic, air infiltration, water infiltration, and aesthetic performance, while meeting
increased thermal performance.
1 Introduction
Curtainwalls on high rise buildings are the art and aesthetics associated with modern architecture
especially in the iconic buildings in a major city center. The architect has a vision of the building that
typically uses a large amount of transparency. This transparency from both the interior and exterior is
what gives the building its most recognizable attributes. The façade must be able to look good while
maintaining structural integrity of ever increasing windloads, thermal loads, and other performance
metrics required by code bodies to ensure the public safety and energy performance of the building.
Building codes keep getting more stringent with regards to energy performance and window to wall
ratio (WWR) to meet prescriptive requirements.
ASHRAE 90.1-2007 for Climate Zone 5 (Chicago, Detroit, Cleveland, Boston) prescribes a
commercial building to have a maximum WWR of 40% and requires that the glazing portion must
have an assembly maximum U value of 14.5 W/m²K. The opaque steel framed wall section is
prescribed to have an assembly maximum U value of 2.1 W/m²K. When calculating the overall U
value of the wall using the area weighting method, it would be (0.4 x 14.5) + (0.6 x 2.1) or U façade =
7.1 W/m²K. This can also be inverted to be the R value of 0.14 m²K/W.
ASHRAE 90.1-2010 for Climate Zone 5 prescribes a commercial building to have a maximum
WWR of 40% and requires that the glazing portion must have an assembly maximum U value of 2.8
W/m²K. The opaque steel framed wall section is prescribed to have an assembly maximum U value of
0.36 W/m²K. When calculating the overall U value of the wall in this situation, it would be (0.4 x 2.8)
+ (0.6 x 0.36) or U façade = 1.3 W/m²K. This can also be inverted to be the R value of 0.75 m²K/W.
This significant change in the prescriptive code has an impact on the assemblies that can be used
for to meet the intention of the code.
The 2010 Florida Building Code has a prescriptive requirement of vision area (window) to have a
U value of 2.55 W/m²K or less, a maximum of 50% vision area and the opaque wall sections to have a
U value of 0.18 W/m²K or less. When calculating the overall U value of the wall in this situation, it
would be (0.5 x 2.55) + (0.5 x 0.18) or U façade = 1.37 W/m²K. Overall the façade has the same
performance requirement in each code. This can also be inverted to be the R value of 0.73 m²K/W.
This simple calculation shows that Florida is willing to embrace 50% glazing and still requiring the
same overall thermal performance. This also highlights the relationship that doubling the thermal
resistance of the opaque assembly does allow the vision area to increase.
The code will provide for options to trade off assemblies provided the building energy model will
show an improvement compared with the base case prescriptive requirements.
Today the curtainwall industry aspires to use 60% or even 70% of glazing due to the architectural
drive for transparency. The glazing assemblies of today are able to meet the prescriptive
requirements at 40% WWR. However the typical spandrel units of the curtainwall assemblies are not
able to meet the prescriptive requirements of the code in the northern climates. This fact in
conjunction with the desire for greater than 40% vision area dictates that curtainwall projects of today
use the alternative method of compliance. Traditional construction indeed has separate opaque wall
sections and vision sections that are easy to decouple. Curtainwalls have opaque (spandrel) sections
that are intimately connected to the vision area by sharing an aluminium frame. This connection of
spandrel and vision cannot be thermally separated. It is nearly impossible for a curtainwall unit with
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 3/18
an aluminium framing system to meet the spirit of the ASHRAE 90.1 requirements, yet the stricter
requirements of the Florida Building Code due to the intimate coupling of the vision and spandrel
sections.
Again, the performance of the facade must meet the prescriptive structural requirements for the
local windloads and seismic aspects. This paper intends to address both the thermal and structural
performance aspects of curtainwall facades.
2 Thermal Performance and Modelling
The three dimensional modelling noted below is for a 1520mm x1520mm spandrel assembly in all
cases.
Figure 1 shows a rendering of a typical curtainwall stick system using Insulating glass vision and
monolithic glass spandrel sections. Today common spandrel sections also can contain double
insulating glass, and metal panels, depending on the architectural influence.
Figure 1. Typical Conventional Stick Curtainwall
This spandrel section uses 100 mm of mineral wool behind the monolithic glazing as insulation and
also as a fire stopping material at the edge of the floor slab. The vision area is a double pane insulating
glass unit with an aluminium spacer and a center of glass U value of 1.8 W/m²K. Three dimensional
thermal modelling of this spandrel system using overall dimensions of 1520mm x1520mm to simulate
real world dimensions provides a U value of 1.16 W/m²K or an R value of 0.86 m²K/W. This
modelling decouples the vision from the spandrel section and accounts for edge effects and effects in
the corners. This calculated thermal performance value is far below the U values suggested by
ASHRAE 2010 (Zones 4-8) of 0.36 W/m²K or the 2010 Florida Building Code of 0.18 W/m²K.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 4/18
Although it would seem quite intuitive and logical to add more insulation to the spandrel cavity the
thermal bridging of the frames makes it quite difficult to insulate the way to compliance.
Figure 2 [1] graphically depicts the diminishing rate of return when applying spray foam to the
internal stud cavities behind an assembly as shown in figure 1.
Figure 2 [2]. Diminishing Rate of Return of Spandrel Section with increased insulation
The ASHRAE Research Project 1365 “Thermal Performance of Building Envelope Details for
Mid- and High-rise Buildings” has a specific comparison of a conventional curtainwall spandrel with
and without spray foam insulation applied in the stud cavities of the internal walls. Lawton and
Roppel [2] reported that “adding insulation to the back-pan has a similar diminishing rate of return for
both systems since the aluminum structural members bypass the pack-pan for both scenarios.” The
use of additional insulation in the back of the spandrel is not going to provide drastic improvements.
Figure 2 depicts that adding additional nominal value of R 5 m²K/W of backpan insulation only
increased the overall thermal resistance from R 0.6 m²K/W to R 0.9 m²K/W.
The increasing depth of back-pan insulation is not going to increase the thermal performance of a
spandrel section with the typical aluminium sections used in today’s curtainwalls.
A proposed solution to this issue is to use a better performing curtainwall system labelled as High
Performance curtainwall. A curtainwall with thermal breaks and a conventional spandrel section is
depicted in Figure 3.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 5/18
Figure 3. Spandrel section of High Performance Curtainwall
When performing the identical three dimensional thermal modelling to this scenario using an
upgraded triple glazed vision assembly with a Center of Glazing U value of 1.0 W/m²K , the spandrel
U value is modelled at 0.89 W/m²K or R value of 1.1 m²K /W. The aluminium system improvements
have made a 31% improvement in the spandrel performance, but they are still very far from
prescriptive requirements.
It has been shown that structural silicone glazing solutions provide increased thermal performance
to curtainwalls. [3] This is primarily due to the fact that the structural silicone is a thermal break on the
outside of the mullion framing system. It would be logical to apply this concept to improve the
performance of conventional spandrels: Use insulation on the exterior of the mullions.
The concept of exterior insulation was modelled and presented at the 2013 Glass Performance Days
conference in Tampere Finland in June of 2013.[4] The concept of using Vacuum Insulation Panels
(VIP) within a spandrel assembly exterior of the mullions showed that a significant upgrade to thermal
performance could be obtained. Modelling was done using Therm 7 software to show the 2
dimensional approach.
Comparisons were made of a double glaze assembly and triple glaze assembly using mineral wool
as the spandrel insulation, using metal clad VIP, and using metal clad VIP in conjunction with mineral
wool (to provide extra fire resistance). Schematic Details of this modelling exercise are captured in
Figures 4-6. The models show a significant upgrade for condensation resistance with the increased
interior temperatures. Increase interior frame temperatures allow increased humidity without fear of
condensation in high performance medical facilities and offices in the northern climates. The models
show decreasing U values that are outlined in Table 1.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 6/18
Table 1. Spandrel Thermal Performance values of the three systems using 2 dimensional modelling of a
1830mm x 2430mm spandrel assembly
Spandrel System
100mm Mineral
Wool
VIP
VIP with 100mm
Mineral Wool
U value W/m²K
0.68
0.32
0.23
R Value m²K /W
1.47
3.1
4.3
Figure 4. Double and Triple glazing in conventional curtainwall application using mineral wool
Figure 5. Double and Triple glazing using metal clad VIP’s as the spandrel panels
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 7/18
Figure 6. Double and Triple glazing using a combination of VIP’s and mineral wool
The above models show the exterior insulation concept will have much more impact on the
spandrel thermal performance values compared to continually adding insulation into the backpan as
depicted in Figure 1 by Lawton and Roppel.
Performance Testing.
Fabrication of Architectural Insulation Modules (AIM) has been done using the concept of placing
the VIP’s within the airspace of an Insulating Glass Unit. This module could then be placed into a
typical curtainwall assembly using typical construction practices. The desire for aesthetic freedom
with regards to colors, patterns and depth in the spandrel section brought about the fabrication of the
Triple Glaze AIM in conjunction with the Double Glaze AIM. The modules could be attached with
structural silicone (figures 5 and 6) or mechanically fastened (Figures 1 and 3). The edge assemblies
are proven performance insulating glass spacer systems that include a rigid warm edge spacer,
desiccant, primary seal of polyisobutylene and a secondary seal of structural silicone. This assembly
will protect the VIPs from damage and aging. This concept is highlighted in Figure 7
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 8/18
Figure 7. Double Glaze AIM with ceramic frit on surface 2 and Triple Glaze AIM with Low E on surface 2
and ceramic frit on surface 4.
The assemblies shown in figure 7 were subjected to hot box testing according to ASTM C1363
using NFRC 100 conditions. The assemblies each measured 1500mm x1500mm x 50mm. The
double glaze used VIPs that were 38mm in thickness between two pieces of 6mm heat strengthened
glass. The triple glaze assembly used two cavities each 16mm thick with three pieces of 6mm heat
strengthened glass. The VIP in the rear cavity was 15mm in thickness, a ceramic frit was applied to
surface #4 and a reflective low E coating was applied to surface #2. The results for these two tests are
provided in Table 2. Comparative benchmark tests were done on vision units made of a standard
25mm low E IG unit with aluminium spacer along with a 44mm Triple IG with two low E coatings
and argon using an aluminium spacer. The identical sized units in table 2 below were all tested without
any framing. The unique size noted above is based on a curtainwall module width of 1520mm using a
63mm wide mullion framing system.
Table 2. ASTM C1363 hot box results.
Assembly
U value
W/m²K
R Value
m²K/W
25mm Double IG
1.87
0.53
44mm Triple IG
1.02
0.98
50mm Triple Glaze AIM
0.48
2.07
50mm Double Glaze AIM
0.30
3.36
These thermal test results of the AIM units are unmatched for a structural panel that is intended to
be used in a spandrel assembly outside of the supporting mullions in a curtainwall.
This data and assembly information were then put into the three dimensional models to understand
the impact that can be obtained.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 9/18
Figure 8 shows a conventional curtainwall comparable to Figure 1in the spandrel area. The Double
Glaze AIM is substituting the monolithic glazing and the mineral wool remains in place. Mineral
wool in this application is kept due to firestopping concerns at the floor slab edge. AIM units increase
thermal performance while additional mineral wool is used to meet smoke, fire, and acoustic
requirements.
Figure 8. Conventional curtainwall with addition of the double glaze AIM.
This spandrel assembly in the three dimensional model provides a U value of 0.54 W/m²K or R
value of 1.8 K/W. This assembly has more than twice the thermal resistance of the stick system
shown in Figure 1. This is due to putting the key insulation on the outside of the mullions. When
referring to Figure 2 we could not fit enough insulation into backpan or stud assemblies to get this
kind of performance.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 10/18
Figure 9 shows a benchmark high performance unitized curtainwall system with triple glaze IG
units that have a center of glass U value of 0.10 W/m²K and the standard 100mm of mineral wool.
Figure 9. Benchmark Unitized Curtainwall using Triple glazing in both vision and spandrel
This benchmark curtainwall has a modelled U value of the spandrel of 1.2 W/m²K.
Figure 10 is the detailing of using the Double Glaze AIM in the spandrel section and Figure 11 is
the detailing of using the Triple Glaze AIM in the spandrel section.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 11/18
Figure 10. Unitized curtainwall using Double Glaze AIM
Figure 11 Unitized curtainwall using Triple Glaze AIM
The three dimensional modelling of the unitized wall utilizing the double glaze AIM (VIP
thickness 38mm showed the Spandrel section U value of 0.39 W/m²K and the model with the Triple
Glaze AIM (VIP thickness 15mm) had a U value of 0.53 W/m²K . The AIMs used in this scenario
represent a tripling and doubling of the thermal resistance.
The double glaze AIM has the most thermal resistance; however the triple glaze AIM has an
architectural appeal due to the flexibility of adding coatings and patterns on surface 2 and a visual
depth in the cavity between surface 2 and 3.
Table 3. Three dimensional modelled results of 1520mm x 1520mm spandrel sections
Assembly
R Value
m²K/W
Typical conventional stick curtainwall
0.86
Conventional stick curtainwall with
Double Glaze AIM (VIP thickness 38mm)
1.85
Typical High Performance stick
curtainwall
1.12
High Performance stick curtainwall
with Double Glaze AIM (VIP Thickness
38mm)
2.45
High Performance stick curtainwall
with Triple Glaze AIM (VIP thickness
15mm)
1.95
Benchmark unitized curtainwall
0.83
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 12/18
Unitized curtainwall with Double Glaze
AIM (VIP Thickness 38mm)
2.59
Unitized curtainwall with Triple Glaze
AIM (VIP thickness 15mm)
1.87
The modelled results presented show that vacuum insulation panels placed within claddings of
glass and aluminium allow curtainwalls to become more thermally efficient than what is in use today
primarily due to the concept of placing the insulation layer on the exterior of the structural mullions
and transoms in a curtainwall.
The hot box test results on full size vision and spandrel glaze assemblies without any framing show
that upgraded thermal performance is available using technology that is readily available. The test
results provide the design community with the assurance that high performance can be obtained in
architecturally pleasing glass based technology that has proven durability performance using edge
assemblies used today with insulating glass technology.
3 Performance Mock-up Testing
The Architectural Insulation Modules (AIMs) are a component of a curtainwall assembly, and very
similar in nature (from a materials, application, and logistics perspective) to standard insulating glass
units. As such, a test to verify the AIMs can perform within its final installed assembly was
considered technically prudent and a necessity for general validation. In maintaining the importance
and value of predictive modelling, emphasis on the value of validation of these modelled results
through testing. Testing for the individual components and for how these individual components
behave and withstand full assembly testing provides the validation and demonstrates that the
Architectural Insulation Module, and its incorporation into curtain wall assemblies, is a proven
solution.
In collaboration with BISEM-USA, a specialist curtainwall design, fabrication, and installation
contractor, a performance mock-up test configuration, the tested curtainwall system, and test
procedure was designed and developed. The system was tested in accordance with AAMA 501 [5], as
published by the American Architectural Manufacturers Association (AAMA), an industry-recognized
and accepted independent performance test standard for air and water resistance, and structural,
seismic and thermal performance. With the latest technologies from Dow Corning and Guardian,
BISEM developed the new curtainwall with a systems approach, providing thermal performance and
also meeting industry established performance criteria for air and water resistance, and structural and
seismic performance.
BISEM contracted with an independent testing facility, Architectural Testing, Inc., to conduct
performance testing on the BISEM Vacuum Wall system mock-up. Actual structural tests confirmed
that the curtainwall would remain in place on the building for both specifically prescribed and
overload conditions, without over deflecting, while also being a component that provides a complete
envelope that defends against air and water infiltration.
3.1 Performance Mock-up Test Configuration and Procedure
The performance mock-up configuration guidelines, test procedures and the associated referenced
standards for individual tests are documented in AAMA 501, Method of Tests for Exterior Walls.
AAMA 501 is an amalgamation of individual test that validate and/or confirm physical performance
attributes of the exterior wall assembly. Some tests were developed through ASTM International
(formerly known as the American Society for Testing and Materials), others established and developed
by AAMA. AAMA 501 is viewed as a widely accepted industry Standard in North American
curtainwall and exteriors wall construction performance testing. Figure 12 shows the designed
configuration of the performance mock-up test, identifying size and location of each of the
components of the assembly.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 13/18
Figure 12. Drawing of Curtainwall Performance Mock-up Configuration
Figure 13 shows the completed installation of the performance mock-up prior to being tested at
BISEM-USA’s facility in Sacramento, California.
Figure 13. Curtainwall Performance Mock-up Configuration
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 14/18
For an appreciation for of the comprehensive nature of the AAM 501 test process, a brief
description of the individual tests conducted and their technical significance is provided.
Air infiltration resistance of the overall curtainwall assembly is tested in accordance with ASTM
E283, Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors [6]. Uncontrolled
air infiltration is contributing factor to several performance characteristics in a curtainwall assembly;
specifically, the capacity to manage water infiltration and the overall energy performance of the
curtain wall. There is a correlation between uncontrolled air infiltration and energy consumption in
commercial buildings. The test measures the amount of uncontrolled air leakage that occurs over the
net area of the test mock-up at a prescribed interior/exterior pressure differential (for commercial
applications) of 300 Pa. With the Architectural Insulation modules as part of the performance mock-
up test, it is possible confirmation of their capacity to function as an air barrier within the context of
the larger system as a standard piece of non-vision insulating glass would.
Water penetration resistance under a constant static pressure is tested to ASTM E 331, Standard
Test Method for Metal Curtain Walls and Doors by Uniform Static Air Pressure [7]. The test
measures the amount of uncontrolled water leakage that occurs over the net area of the test mock-up at
a prescribed interior/exterior static pressure differential of positive 720 Pa (for commercial
applications) for a 15 minute duration. Water, in a prescribed and uniform spray pattern, is applied to
the mock-up at a minimum rate of 3.4 L/m2 min. With the Architectural Insulation modules as part of
the performance mock-up test, it is possible confirmation of their capacity to function as a water
barrier within the context of the larger system as a standard piece of non-vision insulating glass would.
Water penetration resistance under dynamic pressure is tested to AAMA 501.1, Standard Test
Method for Metal Curtain Walls for Water Penetration Using Dynamic Pressure [8]. The test
measures the amount of uncontrolled water leakage that occurs over the net area of the test mock-up at
a prescribed wind speed of 34.3 m/s that is generated by an airplane engine or equivalent. The wind
speed corresponds to an interior/exterior static air pressure differential of 720 Pa (for commercial
applications). Water, in a prescribed and uniform spray pattern, is simultaneously applied to the
mock-up for a 15 minute duration. The generated wind and water spray simulate a high wind and rain
event that may cause water infiltration across the system and/or its joints/interfaces. With the
Architectural Insulation modules as part of the performance mock-up test, it is possible confirmation
of their capacity to function as a water barrier within the context of the larger system as a standard
piece of non-vision insulating glass would. Particularly in a simulated combined wind and rain event.
The structural performance of the curtain wall and the Architectural Insulation Modules are tested
to ASTM E 330, Structural Performance of Exterior Windows, Curtain Walls, and Doors by Uniform
Static Test Method [9]. The specific uniform loading for this test sequence is selected to be a design
pressure of positive and negative 2.4 kPa, and at a 150% proof-loading positive and negative 3.6 kPa.
It is viewed that at the aforementioned design pressure, a large majority of medium to large
commercial projects would be captured within this design parameter. With the test representing a
design wind event, it is important to understand how the Architectural Insulation modules, its atypical
edge seal spacer configuration, and the Vacuum Insulation Panels themselves behave and to confirm
that no deleterious effects are upon those component. The deflection of the framing members cannot
exceed L/175, or 19 mm maximum; where L is the clear span of the framing member. Typically, the
allowable maximum deflection of infill material components is 25 mm maximum. In the instance of
proof-load conditions, there can be no permanent deformation of framing members in excess of 0.02
of the clear span of members. This structural test and can confirm that performance with the
Architectural Insulation Modules as a part of the performance mock-up confirms the modules
capacity to provide to transfer loads to the curtainwall framing member whilst not over deflecting and
not negatively impacting the edge seal configuration and/or the Vacuum Insulation panels.
Interstory vertical differential movement is tested to AAMA 501.7, Recommended Static Test
Method For Evaluating Windows, Window Wall, Curtain Wall And Storefront Systems Subjected To
Vertical Inter-Story Movements [10]. Three complete cycles are performed in the vertical direction at
the simulated floor slab at a movement magnitude of 19mm. This test simulates the day-to-day live
load deflection of a floor slab. Whilst the test is more of a movement capacity confirmation of the
curtain wall system itself, some in-plane loading does occur in the glass (and hence the Architectural
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 15/18
Insulation Modules) and verification sought to ensure the movement is not negatively impacting the
edge seal configuration and/or the Vacuum Insulation panels.
Interstory lateral differential movement is a test that confirms a curtain wall system capacity to
manage movement caused by high wind or seismic events (whichever governs). The test is conducted
in accordance with AAMA 501.4, Recommended Static Test Method for Evaluating Curtain Wall and
Storefront Systems Subjected to Seismic and Wind Induced Interstory Drifts [11]. Three complete
cycles are performed in the horizontal direction at the simulated floor line. Testing was conducted at
lateral movements up to 47 mm (Δs), and at a maximum of 89 mm (ΔM) of interstory drift. Whilst the
test is more of a movement capacity confirmation of the curtain wall system itself, some in-plane
loading does occur in the glass (and hence the Architectural Insulation Modules) and verification
sought to ensure the movement is not negatively impacting the edge seal configuration and/or the
Vacuum Insulation panels.
A summary of the test procedure and sequence of the test conducted follows:
1. Pretesting
2. Air infiltration test Static Pressure
3. Water infiltration test Static
4. Water infiltration test Dynamic
5. Structural test Uniform Load Design Load
6. Repeat - Water infiltration test Static Pressure
7. Repeat - Water infiltration test Dynamic Pressure
8. Interstory Vertical Displacement
9. Repeat - Water infiltration test Static
10. Repeat - Water infiltration test Dynamic Pressure
11. Interstory Horizontal Displacement
12. Repeat - Water infiltration test Static
13. Repeat - Water infiltration test Dynamic Pressure
14. Structural Test Uniform Load Proof Load (over load)
15. Interstory Horizontal Displacement (seismic) Proof
The repeat static and dynamic water infiltration test after structural and movement capacity test are
meant to confirm the performance characteristic of the curtain wall assembly after each of these events.
If a non-conforming performance occurs at any of these stages, a reason for the failure can be
attributed to a specific event on the test process.
3.2 Performance Mock-up Test - Results
Table 4 is a summary of the results of the performance mock-up test. It can be seen that the criteria
established in the test procedures were met, and qualitative observation of the Architectural Insulation
Modules after testing showed no deleterious effects to the edge seals or the Vacuum Insulation
Modules.
Table 4. Summary of Final Test Results
Test
Measured
Allowed
Result
Preload @ + 1.2 kPa
N/A
N/A
N/A
Air Infiltration Test
Static Pressure @ 300 Pa
0.05 L/s m2
0.3 L/s m2
PASS
Water Infiltration Test
Static Pressure @ 720 Pa
No uncontrolled
leakage
No uncontrolled
leakage
PASS
Water Infiltration Test
Dynamic @ 720 Pa
No uncontrolled
leakage
No uncontrolled
leakage
PASS
Structural Test Uniform Load
Design Load @ +/-1.2 kPa; +/- 2.4 kPa
See Figure 15
See Table 5
See Figure 15
See Table 5
PASS
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 16/18
Repeat - Water Infiltration Test
Static @ 720 Pa
No uncontrolled
leakage
No uncontrolled
leakage
PASS
Repeat - Water Infiltration Test
Dynamic @ 720 Pa
No uncontrolled
leakage
No uncontrolled
leakage
PASS
Interstory Vertical Displacement
3 Cycles @ 19mm
No visible
damage
No visible
damage
PASS
Repeat - Water Infiltration Test
Static @ 720 Pa
No uncontrolled
leakage
No uncontrolled
leakage
PASS
Repeat - Water Infiltration Test
Dynamic @ 720 Pa
No uncontrolled
leakage
No uncontrolled
leakage
PASS
Interstory Horizontal Displacement
3 Cycles @ 47mm
No visible
damage
No visible
damage
PASS
Repeat - Water Infiltration Test
Static @ 720 Pa
No uncontrolled
leakage
No uncontrolled
leakage
PASS
Repeat - Water Infiltration Test
Dynamic @ 720 Pa
No uncontrolled
leakage
No uncontrolled
leakage
PASS
Structural Test Uniform Load
Proof Load @ +/- 1.8 kPa; +/- 3.6 kPa
See Figure 15
See Table 6
See Figure 15
See Table 6
PASS
Interstory Horizontal Displacement
Proof Load @ 89mm
No visible
damage
No visible
damage
PASS
Figure 14 shows the placement of the linear transducers on the performance mock-up to measure
the relative deflection of key components during the structural capacity test. Figures 14 and 15
represent the location of the transducers on the Architectural Insulation Modules.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 17/18
Figure 14. Elevation Showing Transducer Locations for Mock-up
Figure 15. Location of Transducer on the Architectural Insulation Module
Table 5 shows the relative deflection of the Architectural Insulation Modules under design pressure
of 2.4 kPa. Transducer #11 is placed at the mid-point of the Architectural Insulation Module.
Transducer #12 is placed at an adjacent mullion. The difference between the two values is the relative
deflection of the Architectural Insulation Module.
Table 5. Uniform Load Deflection at Architectural Insulation Module at Design Pressure
Indicator
Location
Positive
2.4 kPa
Net
Deflection
Negative
2.4 kPa
Net
Deflection
Allowed
Result
11
32 mm
16 mm
50 mm
21
25
PASS
12
16 mm
--
29 mm
--
--
--
Table 6 shows the permanent set (or permanent deformation) values of the Architectural Insulation
Modules under proof-load pressure of 3.6 kPa. Transducer #11 is placed at the mid-point of the
Architectural Insulation Module. Transducer #12 is placed at an adjacent mullion. The difference
between the two values is the relative permanent set of the Architectural Insulation Module.
Table 6. Permanent Set of the Architectural Insulation Module at Proof-Load Pressure
Indicator
Location
Positive
3.6 kPa
Net
Deflection
Negative
3.6 kPa
Net
Deflection
Allowed*
Result
11
0.8 mm
0.3 mm
0.3 mm
0 mm
--
PASS
12
0.5 mm
--
0.3 mm
--
--
--
*General Note: Allowable amounts are based on 0.02 of their clear span for framing members.
4 Conclusions
The study concludes that higher performing curtainwalls can be achieved without sacrificing the
existing structural, seismic, air infiltration, water infiltration, and aesthetic performance, while meeting
increased thermal performance. The Architectural Insulation Modules not exhibit deleterious effects
when subjected to air water, structural, and seismic loading. The edge seals were observed to maintain
their integrity and the Vacuum Insulation Panels did not appear affected by the repeated loading
conditions of the AAMA 501 test regimen.
Lawrence D. Carbary, Stanley Yee, Nick Bagatelos Architecture Insulation Modules 18/18
It is likely that most curtainwalls will need to go through an alternative method of compliance to
meet the spirit of the codes of today and in the future due to the architectural drive for high share of
vision area. Curtainwalls use aluminium framing to couple the vision and opaque areas of the wall
and the spirit of the codes is still within conventional construction where these areas are separate.
The modelled results of the unitized curtainwall with a double glaze AIM approach the ASHRAE
2010 requirement for opaque assemblies. Proprietary curtainwall systems and astute curtainwall
engineers will be able to maximize the performance of this type of assembly to meet prescriptive
individual project requirements.
The Architectural Insulation Modules (AIMs) described here provide the architectural community
another tool to use to maximize the transparency of the wall while still meeting the code.
References
[1] ASTM C1363-11 Standard Test Method for Thermal Performance of Building Materials and
Envelope Assemblies by Means of a Hot Box Apparatus
[2] Lawton, Mark, and Roppel, Patrick, Thermal Performance of Curtain Wall Spandrel Panels,
Solutions MH, Volume 2011, Issue 1.
http://www.morrisonhershfield.com/newsroom/technicalpapers/Pages/ThermalPerformanceofCurt
ainWallSpandrelPanels.aspx viewed September 27, 2013
[3] Carbary, L. D., Hayez, V., Wolf, A. T., Bhandari, M. Comparisons of Thermal Performance and
Energy Consumption of Facades Used in Commercial Buildings, Glass Performance Days 2009,
Tampere Finland, http://www.glassfiles.com/articles/comparisons-thermal-performance-and-
energy-consumption-facades-used-commercial-buildings viewed September 27, 2013
[4] Dunlap, A., Carbary, L. D., O’Connor, T. F., High Performance Curtainwall Using Vacuum
Insulated Panel (VIP) Spandrels, Glass Performance Days 2013, Tampere Finland,
http://www.glassfiles.com/articles/high-performance-curtain-wall-using-vacuum-insulated-panel-
vip-spandrels
[5] AAMA 501, Method of Tests for Exterior Walls, (2005). American Architectural Manufacturers
Association.
[6] ASTM E283, Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors. ASTM
International, formerly known as the American Society for Testing and Materials.
[7] ASTM E 331, Standard Test Method for Metal Curtain Walls and Doors by Uniform Static Air
Pressure. ASTM International.
[8] AAMA 501.1, Standard Test Method for Metal Curtain Walls for Water Penetration Using
Dynamic Pressure. American Architectural Manufacturers Association.
[9] ASTM E 330, Structural Performance of Exterior Windows, Curtain Walls, and Doors by
Uniform Static Test Method. ASTM International.
[10] AAMA 501.7, Recommended Static Test Method For Evaluating Windows, Window Wall,
Curtain Wall And Storefront Systems Subjected To Vertical Inter-Story Movements. ASTM
International.
[11] AAMA 501.4, Recommended Static Test Method for Evaluating Curtain Wall and Storefront
Systems Subjected to Seismic and Wind Induced Interstory Drifts. ASTM International.
... Insulated spandrel helps to curtail convective heat fluxes. The insulation also acts as a fire-stopping material at the edge of the floor slab [20]. However, topics on insulated spandrel sections are marginally considered in the literature [21,22]. ...
... Even with a thermally broken aluminum frame and a triple glazing Insulated spandrel helps to curtail convective heat fluxes. The insulation also acts as a fire-stopping material at the edge of the floor slab [20]. However, topics on insulated spandrel sections are marginally considered in the literature [21,22]. ...
... For instance, the typical curtain wall shown in Figure 1 utilized 100 mm thick mineral wool insulation. Even with a thermally broken aluminum frame and a triple glazing system, center-of-glazing and spandrel U-values of 1 W/m 2 K and 0.89 W/m 2 K were estimated for the system, respectively [20], which were very far from the requirements defined in energy codes like ASHRAE 90.1. Generally, most opaque insulated spandrels do not satisfy the prescriptive insulation values or effective U-values for cold climates [35]. ...
Article
Full-text available
Almost every major city’s skyline is known for high-rise iconic buildings with some level of curtain wall system (CWS) installed. Although complex, a CWS can be designed for energy efficiency by integrating insulated spandrel components in space-constrained areas, such as slabs/plenums. The main aim of this study was to experimentally examine the thermal performance of an optimized curtain wall spandrel system integrated with vacuum insulation panel (VIP) as spandrel insulation. The study is based on robust experimental evaluations, augmented with appropriate numerical computations. The main study is constituted of six parts: (1) evaluation of VIP specifications and thermal properties; (2) analysis of VIP spandrel configuration, fabrication, and installation in a test building facility; (3) thermal bridge characterization of VIP spandrels; (4) monitoring and assessment of VIP durability within the spandrel cavities; (5) thermal performance analysis; and (6) assessment of related limitations and challenges, along with some further reflections. In all, 22 VIPs (each of size 600 mm2) were used. The effective thermal conductivity of VIPs ranged from 5.1–5.4 (10−3 W/mK) and the average value for initial inner pressure was approximately 4.3–5.9 mbar. Three VIP spandrel cases were fabricated and tested. The results proved that the Case 3 VIP spandrel configuration (composed of a double-layer VIP) was the most improved alternative for integrating VIPs.
... It may not be uncommon to decrease the WWR to 61% by reducing the glass height to 2438mm (8 ft) and increasing the height of the shadow box to 1524mm (5 ft). Opaque assemblies of 1524mm x 1524mm (5 ft x 5 ft) have been studied and modeled previously [8][9] in this same spirit, however the assemblies studied were not shadow box designs. Given the history, the constraints of the test apparatus and the typical dimensions used in the industry today, the team of authors determined three assemblies would be used, as noted as Test A, Test B and Test C. ...
... ther or not including the adjacent vision sections has a meaningful impact on the test outcome. Test C is a shadow box assembly with dimensions of 1524mm x 1524mm (5 ft x 5 ft). Aside from the increase in height this sample is identical to Test B previously described. The purpose of this sample was for comparison with the outcome of previous tests. [8][9] 2.2 Options 1, 2, 3 & 4 – Variations on the Shadow Box Insulation Furthermore, four insulation configurations were tested in framing systems A, B & C and will be furthermore referred to as insulation options 1, 2, 3, and 4. These assemblies are highlighted inFigure 2.3. On the left hand side of the figure the insulation panels are sh ...
... s show that the accuracy of the simulation does indeed depend on the physical configuration of the test sample (A-C) and insulation (1-4) chosen. Furthermore, they suggest that the level of error in the simulation increases with the actual R-value of the sample evaluated. This has been recently reported in non-shadowbox curtain wall spandrel cases. [8][9] Another metric by which the accuracy of the U-factors determined can be evaluated is gained by observing the equivalency criteria dictated by the NFRC 100 standard. The most recent version identifies that numerical modeling and test equivalency are established by the standard when the simulated U-factor is within 10% of the tested va ...
Conference Paper
Full-text available
Research was performed to establish the merits of utilizing fumed silica vacuum insulation panels (VIP) and aerogel enhanced fabrics in the construction of curtain wall spandrel areas; specifically, with the aim of considering potential performance improvements and novel esthetic possibilities. In doing so, a thermally isolated framing system adapted from plans for a commissioned building was chosen as a benchmark and detailed according to conventional practices commonly employed for unitized curtain wall construction. Spandrel assemblies incorporating this framing system with various applications of insulating materials were evaluated by the FEM (finite element method) and compared to results obtained from experimental evaluation. Respectively the software program Therm 6.3[1] and the ASTM C 1363[2] procedure were used with NFRC100 [3] environmental conditions. With regard to geometry, two unique compositions were employed for the study consisting of both a spandrel area isolated from adjacent vision areas and spandrel area with adjacent vision areas above and below the spandrel. In the latter case, both a fixed head rail and stack joint were included. The physical dimensions of the samples varied from 900mm x 1500mm to 1500mm x 2130mm (3 ft x 5 ft to 5 ft x 7 ft). The results of the work established that thermal modeling techniques can be proven to predict spandrel area thermal transmittance with reasonable accuracy when compared to an accepted industry test standard. Furthermore, the merits of the innovating the insulation technologies proposed are addressed quantitatively and the results are projected for a range of typical curtain wall assemblies.
... To further understand and improve CWS with integrated VIP spandrels (CWS-VIP sp.), some studies have focused on condensation risk, U -value and thermal resistance ( R -value) evaluations, and structural performance issues based on experimental and numerical methods [53,56,57] . However, during the thermal performance assessments discrete thermal bridges due to component VIP were either simplified or not reported in detail, thus the actual insulation performance will be of some magnitude inferior to expected outcomes. ...
... Firstly, Physibel TRISCO (v.13 w) was used to model and examine the performance of a VIP spandrel measuring 1500 mm × 1500 mm × 50 mm, according to ISO 10211. To validate the model, simulation results were compared to experimental results carried out with a hot box apparatus in compliance to ASTM C1363 [57] . TRISCO is a thermal analysis program for steady state heat transfer in three-dimensional objects consisting of different materials and submitted to different boundary conditions, using finite difference method [60] . ...
Article
The thermal and energy performance of curtain wall façades can be improved by incorporating spandrel units in areas such as slabs/plenums to hide existing building services or areas where concealment of in- door space is required. The main objective of this study was to numerically investigate the performance of curtain wall façade with integrated vacuum insulation panel (VIP) as spandrel insulation. The main study constitutes six parts: (1) concept and derivation of governing equations, (2) model and its validation, (3) VIP integration alternatives, (4) overall thermal performance considering 2D/3D thermal bridges and internal surface temperatures, (5) building energy and vision-spandrel ratio effect, and (6) limita- tions and challenges. Thermal behavior of the system was characterized via 3D heat transfer simulations using Physibel TRISCO according to EN ISO 10211, while dynamic building energy analysis was carried out using EnergyPlus based on a stereotypical office building unit, in relation to the humid continental climate of Incheon, Republic of Korea. The baseline model was validated with experimental data from previous study, and a marginal discrepancy less than 4% was found between them. Further, the validated model was developed into different spandrel configurations, seeking to mitigate thermal bridges while improving insulation performance, by varying VIP integration design. Results indicated that the best VIP spandrel alternative improved thermal performance of the system by about 30%. Moreover, year-round space heating and cooling energy reductions were realized by gradually increasing the spandrel area by ratio from 0% to 80%, howbeit at the expense of electrical lighting energy. Finally, some noteworthy limitations of the study and challenges related to VIP integration into curtain wall spandrel have been duly discussed.
Article
Curtain wall façades have been embraced worldwide as a key sign of modern architecture. To improve the thermal characteristics and energy performance of curtain wall systems (CWS), insulated spandrels are installed between glazing sections. However, there are some noteworthy space-technical constraints. Firstly, CWS are structurally supported by frame systems. The inner length (interior projection) of a curtain wall frame is related to its structural requirements. When high structural performance is not needed, inner length is usually shortened. However, the inner length also creates space for insulation. Due to this space problem, even when high structural performance is not required, the inner length is still enlarged to accommodate the required thickness of insulation. Also, spandrel sections with thick insulated back panels are conventionally installed behind monolithic glazing or opaque claddings between slab/plenum areas of adjacent floors and hidden from the view of building users. Otherwise, aesthetics is compromised due to protrusions. Thus, total area to install insulation in curtain wall façades is traditionally defined and limited to slab/plenum areas only. Consequently, there could be undesirable increase or decrease of window-to-wall ratio as well as restriction of design freedom. Such slim façades require thin and high-performance insulation solutions. Among super-insulating materials currently available, vacuum insulation panel (VIP) is a good go-to insulator to be integrated into curtain wall spandrels. This study seeks to present a comprehensive review on CWS integrated with VIP as spandrel insulation. Depending on the level of prefabrication and how they are built, CWS can broadly be categorized into stick, unitized, and structural glazing systems. Curtain walls differ significantly from conventional windows in that curtain walls are anchored from floor slabs of a building (hangs like a curtain) whereas windows are mounted between floor slabs. Throughout literature, VIP integrated into CWS is composed of fumed silica core material and encapsulated in a metalized laminate (Si-VIP). Under severe accelerated aging conditions, studies proved that VIP spandrel modules provided ten times protection to the VIPs as compared to standalone VIPs. The concept represents a strategy to extend the service life and in-service durability of VIPs, while improving the energy consumption footprint of CWS. As far as the authors know, this paper is the first state-of-the-art review covering CWS integrated with VIP spandrels. Finally, current challenges and future research opportunities concerning VIP integration in CWS are explored.
Thermal Performance of Curtain Wall Spandrel Panels
  • Mark Lawton
  • Patrick Roppel
Lawton, Mark, and Roppel, Patrick, Thermal Performance of Curtain Wall Spandrel Panels, Solutions MH, Volume 2011, Issue 1.
High Performance Curtainwall Using Vacuum Insulated Panel (VIP) Spandrels, Glass Performance Days
  • A Dunlap
  • L D Carbary
  • T F O'connor
Dunlap, A., Carbary, L. D., O'Connor, T. F., High Performance Curtainwall Using Vacuum Insulated Panel (VIP) Spandrels, Glass Performance Days 2013, Tampere Finland, http://www.glassfiles.com/articles/high-performance-curtain-wall-using-vacuum-insulated-panelvip-spandrels
American Architectural Manufacturers Association
AAMA 501, Method of Tests for Exterior Walls, (2005). American Architectural Manufacturers Association.