Tag Archives: 07 21 00–Thermal Insulation

Continuing Education on Continuous Insulation

continuous - Tom's article 2015 - 5th-&-Alton Shopping-Center

All images courtesy Sto Corp.

by Tom Remmele, CSI
Continuous insulation (ci) has been a component of exterior wall assemblies for more than 40 years in North America and even longer in Europe. It has always been the smart way to design wall assemblies from the standpoint of energy conservation and water management. By minimizing energy loss caused by thermal bridging and the risk of condensation caused by water vapor diffusion, exterior ci can improve building durability and benefit the environment.

Standards-writing and regulatory bodies, government agencies, and the building science community are in alignment in viewing exterior ci as a sensible strategy to conserve energy in buildings. The American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) has steadily driven energy conservation standards—and hence, the International Energy Conservation Code (IECC)—to ci prescriptive R-value requirements (in combination with stud cavity insulation) as a pathway to greater energy conservation in buildings.

In sponsoring the 2012 IECC code changes, the Department of Energy (DOE) helped achieve the “largest one-step energy efficiency increase in the history of our energy code.” Building Science Corporation identifies the ‘perfect wall’ (i.e. one working in any climate zone), as having ci outbound of the structure. Thus, for the foreseeable future ci is likely to be a fixture in most exterior wall assemblies.

Types of foam plastic ci
Figure 1 summarizes properties of rigid cellular polystyrene and polyisocyanurate (polyiso) thermal insulations as published in ASTM C578-14, Standard Specification for Rigid, Cellular Polystyrene Insulation, and ASTM C1289-14, Standard Specification for Faced, Rigid Cellular Polyisocyanurate Thermal Insulation Board, respectively. Commonly used insulating materials conforming to these property requirements are Type I expanded polystyrene (EPS), Type IV extruded polystyrene (XPS), and Type I, Class 1 or 2 polyiso.

ContinuousInsulation_Figure1

Common types of rigid foam plastic continuous insulation (ci) used in exterior wall assemblies.

Each insulating material has its own benefits and limitations influencing which one should be used for a given project. For example, EPS is the insulation commonly used in exterior insulation and finish systems (EIFS) because of its dimensional stability, water vapor permeability, and adhesion compatibility with EIFS adhesives and base coats. Due to their higher R-values, XPS and polyiso boards are more commonly used behind brick veneer to allow for thinner wall sections. This becomes important when considering the total thickness of a brick veneer cavity wall with ci and the implications on size and thermal bridging of supporting shelf angles and lintels.

Water vapor permeability of the insulating material can be an advantage or disadvantage. For example, in hot, humid climate zones where vapor drive is predominantly inward, exterior polyiso or XPS insulation can retard inward vapor drive and reduce the potential for condensation on the relatively cold conditioned surface of interior drywall over metal studs. In mixed climates, where vapor drive is both inward and outward for long periods during the course of a year, EPS ci is advantageous because its higher vapor permeability allows water vapor to diffuse, which aids in drying of the wall assembly in the event of condensation.

A wall analysis during design is a valuable tool for selecting the best type of ci material in this regard. Dynamic computer models are a good approach, since they characterize wall assembly hygric performance through seasonal change, but even a simplified steady-state analysis for worst case winter and summer months can be a helpful tool to assist in making material choices for a given wall assembly.

Other things to consider beyond physical properties are jobsite handling, storage, and compatibility with other materials, as well as the construction Type, whether Types I−IV or Type V, and design wind pressure requirements. EPS and XPS have limited ultraviolet (UV) resistance and should not be left exposed to sun for extended periods as the surface will degrade (chalk).

While this degradation has no significant effect on R-value, it can interfere with adhesion of joint treatments, tapes, EIFS base coats, and membrane materials that rely on adhesion to the surface, unless the surface is rasped or sanded to remove the chalked material. Chalking is not an issue when the insulation is ‘faced’ with glass mat facing or aluminum foil facing as with most polyiso boards, although adhesion to the facing materials still has to be evaluated.

Equally important to consider (if not more so) on jobsites is the combustibility of foam plastics. They should be protected from sparks, flame, or any other source of ignition. All foam plastic insulation boards are produced with flame retardant, but they behave differently in the presence of flame; while EPS and XPS melt, polyiso chars.

Despite their combustibility, all these foam plastic insulating materials can be used on buildings required to be of noncombustible construction (Types I−IV) with proper material and ‘end use’ testing to support the proposed assembly. Likewise, they can all be used in wind-resistant assemblies provided they are constrained (i.e. sandwiched) in the negative and positive direction by another material (e.g. sheathing/cladding) capable of resisting design wind pressures. Alternatively, appropriate tests can be performed to determine wind load resistance of the insulation relative to project and/or building code requirements.

Fire safety considerations
Fire safety in the design of foam plastic-based wall assemblies is an important factor when considering their use. Since such materials are combustible, building codes strictly regulate the use of foam plastics. Chapter 26 of the 2015 International Building Code (IBC) has seven requirements that must be met for foam plastics to be approved for use in walls (Figure 2).

CS Feb FIgure 2 (2)

Summary of the 2015 International Building Code (IBC) Chapter 26 requirements for use of foam plastic insulation in exterior wall assemblies.

For the design professional, listing and labeling of the insulation by an approved independent third party is the first step in verifying code compliance. Most insulation board manufacturers hold International Code Council Evaluation Service (ICC-ES) evaluation reports (ESRs), or Underwriters Laboratory (UL) or other listings, simplifying verification.

These listings also demonstrate other aspects of code compliance, for example, compliance with flame spread and smoke development criteria to qualify as a Class A building material, or special uses such as below-grade or attic insulation. Other code compliance requirements are more difficult to verify because they involve wall assembly tests that may exist with the insulation board manufacturer, the cladding manufacturer, or, in some cases, with the air barrier/water-resistive barrier (WRB) manufacturer.

Potential heat, a measure of the foam plastic’s stored heat energy, is a function of the type of foam plastic insulation, its thickness, and density. IBC effectively limits potential heat for construction Types I−IV to the insulation thickness and density successfully tested in the National Fire Protection Association (NFPA) 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components.

NFPA 285 is a qualifying wall assembly test for the use of foam plastic in wall assemblies of Types I, II, II, or IV construction. As a ‘worst-case’ surrogate for exterior wall fires, the test addresses the effects of a simulated fire in an interior room and vertical flame propagation from floor-to-floor and room-to-room vertically and laterally. An example of an assembly that meets NFPA 285 acceptance criteria is shown in Figure 3, and the actual test is depicted in Figure 4.

continuous_61s01

Figure 3: Exterior brick veneer wall assembly with ci that complies with National Fire Protection Association (NFPA) 285 acceptance criteria (refer to International Code Council Evaluation Service Reports (ICC-ESRs) 1233 [6] 2141[7]).

continuous_NFPA 285 Test

Figure 4: As shown above, NFPA 285 test exposes the wall assembly to fire from an interior compartment and evaluates vertical and lateral flame propagation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

While the test enables approval of the assembly in Types I−IV construction, it also establishes limits—maximum allowable thickness and density of insulation and detailing around the opening that must conform to (or be more conservative, from a fire protection standpoint) what was tested. Test results can sometimes be extended to other claddings or backup wall construction when evaluated by a qualified fire protection engineer.

For example, in Figure 3, the results of the fire tests with masonry veneer over steel stud wall construction were extended to backup wall construction of concrete or concrete masonry unit (CMU) in lieu of steel stud with gypsum sheathing. Once again, ICC-ES evaluation reports can be a valuable resource for the design professional to know what assemblies have been tested and meet acceptance criteria, or where results of tests have been extended, evaluated, and recognized by ICC-ES.

NFPA 285 is not the only assembly test to be considered. ASTM E119-12a, Standard Test Methods for Fire Tests of Building Construction and Materials, is necessary when walls are required to have an hourly fire-resistance rating—a common requirement for commercial office, institutional, and some retail and multi-family type construction. The test evaluates the ability of the assembly to resist temperature rise, collapse, flaming, or ignition on the unexposed side of the assembly.

If the assembly is asymmetrical, it must be tested from both sides—in other words, with the fire originating from the interior or exterior. Further, the effects of a hose stream (used to provide additional structural evaluation) are evaluated to ensure the unexposed side remains intact and there is no breach or collapse of the assembly as a result of the hose stream.

Engineering analysis or modeling by a qualified fire protection engineer can be done to qualify substitute materials or to make minor revisions to what was tested to provide the design professional with a wider range of material options for the wall assembly. For example, if an hourly rating is achieved with a frame wall assembly with gypsum sheathing on the exterior and gypsum wall board on the interior, it is readily assumed a ‘mass wall’ fire-resistive wall construction (e.g. 152-mm [6-in.] cast-in-place concrete or 203-mm [8-in.] CMU) would provide equal or better resistance than the frame wall with the same exterior ci and cladding assembly. ICC-ES evaluation reports, UL listings, and Gypsum Association’s (GA’s) Fire Resistance Design Manual are valuable resources for the design professional to identify tested fire-resistance rated wall assemblies.

The last of the assembly tests is NFPA 268, Standard Test Method for Determining Ignitability of Exterior Wall Assemblies Using a Radiant Heat Energy Source. The test evaluates a wall assembly’s susceptibility to ignite from the radiant heat produced by a fire in an adjacent building. It is an important test for EIFS and other foam plastic-based wall assemblies that do not conform to one of the six wall covering exceptions listed in Section 2603.5.7 of the 2015 IBC:

  • 
minimum 15-minute thermal barrier;
  • 
minimum 25-mm (1-in.) of concrete or masonry;
  • 
at least 9.5-mm (38-in.) glass-fiber-reinforced concrete (GFRC);
  • 
metal-faced panels meeting the prescribed composition and thickness;
  • 
minimum 22.2-mm (78-in.) stucco; and
  • 
minimum 6-mm (14-in.) fiber cement lap, panel, or shingle siding.

A final requirement of the code for all types of construction is separation of the combustible foam plastic insulation from interior space with a 15-minute thermal barrier, typically 13-mm (12-in.) interior drywall or exterior gypsum sheathing. Commercial attic space or the interior wall area above suspended ceilings must have this 15-minute thermal barrier in place on the interior if it does not exist on the exterior side of the wall to separate the foam plastic insulation (with some exceptions permitted in the 2015 IBC’s Section 2603.4.1). Between-the-stud fiberglass batt insulation does not count as a thermal barrier since it is discontinuous.

Thus, building codes strictly regulate the use of foam plastics in wall assemblies. Manufacturers of wall assembly components—cladding, ci, air barrier, and sheathing—must demonstrate compliance with these requirements. ICC ESRs are an excellent resource to facilitate verification of wall assembly compliance.

Moisture-related durability considerations
One of the ways exterior ci can help in managing water is by changing the location of the dewpoint in cold climate zones so water vapor diffusion condensation potential is minimized or eliminated. Continuous insulation can also aid in controlling moisture in hot humid climate zones as demonstrated in recent research conducted by the US DOE and the EIFS Industry Members Association (EIMA). The research compared the hygrothermal performance of various wall assemblies—EIFS, stucco, brick, and fiber cement siding (15 assemblies in total)—installed on a test hut (Figure 5) exposed to natural weather in Hollywood, South Carolina (Climate Zone 3A).

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Figure 5: The image to the left shows an EIFS Industry Members Association/Department of Energy (EIMA/DOE) test hut in Hollywood, South Carolina with wall panels monitored for a two-year period for hygrothermal performance. On the right, the test hut rainwater collection device ‘delivers’ rain into the panel at the plane of the water-resistive barrier (WRB) during the second year of exposure. The device was intended to simulate a flaw (breach) in the panel exterior wallcovering.

Temperature, heat flux, relative humidity (RH), and moisture content measurements were taken 24 hours a day with sensors placed in the wall panels. After a little more than a year of exposure, a flaw (i.e. opening) was created in some of the wall panels to introduce rainwater onto the plane of the WRB behind the cladding. The cladding with ci performed the best from the standpoint of temperature and moisture control as measured by the heat flux sensor on the inside face of interior gypsum wallboard and the relative humidity sensor on the face of the wall sheathing directly behind the WRB (Figure 6).

continuous_EIMA Test Hut Data Profiles

Figure 6: Assembly with exterior ci shows improved moisture control in comparison to assemblies without ci as indicated by relative humidity (RH) measurements at the exterior face of the sheathing. The assemblies were installed over nominal 2×4 wood framing. In order, they are (a) 102-mm (4-in.) brick veneer cavity wall over paper water-resistive barrier (WRB) on 11-mm (7/16-in.) oriented strandboard (OSB) with unfaced R-11 batt insulation, (b) 102-mm exterior insulation finish system (EIFS) with fluid-applied air barrier/WRB on 13-mm (1/2-in.) plywood with no batt insulation, and (c) 22-mm (7/8-in.) portland cement stucco over two layers of paper WRB on 11-mm OSB with unfaced R-11 batt insulation.

The closer the heat flux sensor stayed to the zero base line (which would represent constant interior temperature), the better the assembly’s thermal performance. An average monthly relative humidity of below 80 percent was considered acceptable based on ASHRAE STP 160, Criteria for Moisture-control Design Analysis in Buildings. The ci assembly proved not only to be best from a thermal standpoint, but also kept wall components dry, even when rain was deliberately directed into the assembly during the second year of exposure. This is important not only from the standpoint of durability, but also because insulation, if it stays moist, loses some of its insulating value.

Key factors in the moisture control success of the ci assembly were:

  • 
exterior ci kept wall sheathing above the dewpoint during winter;
  • 
combination of low water absorption exterior finish materials and relatively low water vapor permeability of the insulation prevented high exterior RH in summer from significantly increasing the sheathing’s relative humidity;
  • 
seamless fluid-applied air barrier/WRB behind the cladding was effective in resisting air leakage (and condensation potential) and was unaffected by the rain introduced into the wall during the second year of exposure (the other claddings had paper WRBs); and
  • 
drainage feature of the ci assembly prevented excess amounts of rain from accumulating in the assembly.

Conclusion
As building codes have evolved to the point where ci is now mandatory for many wall assemblies, rigid foam plastic ci wall assemblies have become more prevalent than in the past. They have special design considerations that need to be addressed at the design stage with an awareness of what the building code requires in relation to the use of foam plastics and their effects on the physics of the wall construction, as well as design details.

While this feature looked at the basic types of materials available, and focused on fire safety and moisture-related durability, this author is also developing another technical article that explores the added complexity of design details, along with structural considerations, environmental impacts, and cost control for a future issue of The Construction Specifier.

Tom Remmele, CSI, is the director technical services/R&D for Sto Corp., a manufacturer of air barriers, coatings, exterior insulation and finish systems (EIFS), and stucco products. He has held technical management positions in the construction industry for more than 25 years. Remmele is a past Technical Committee chair of the EIFS Industry Members Association (EIMA). He can be reached at tremmele@stocorp.com.

Meeting Efficiency Codes without Compromising Design: Technology that Meets Specifications

A full-scale mockup incorporating architectural insulation modules.  [CREDIT] Photo courtesy Dow Corning Corporation

A full-scale mockup incorporating architectural insulation modules. Photo courtesy Dow Corning Corporation

by Stanley Yee, LEED AP

To help overcome concerns about adoption of new technology, a full-scale mockup of a high thermally performing curtain wall incorporating architectural insulation modules was recently successfully tested by an independent third-party. Testing was conducted in accordance with American Architectural Manufacturers Association (AAMA) 501, Methods of Test for Exterior Walls, ensuring acceptable performance for air and water penetration resistance, structural capacity, and vertical and seismic movement requirements.

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Meeting Efficiency Codes without Compromising Design

Photo courtesy of University of Birmingham

Photo courtesy of University of Birmingham

by Stanley Yee, LEED AP

Creating an effectively insulated envelope is necessary for buildings to meet the latest demands of ever-tightening energy codes. Innovative use of high-performance insulation technologies enables architects to achieve improved insulation performance using common building techniques without sacrificing aesthetics.

Thin-profile, high-performance insulation materials that seamlessly integrate into conventional glazing systems now give designers flexibility to better manage and balance thermal performance and façade aesthetics. Materials such as vacuum insulation panels (VIPs), architectural insulation modules (AIMs), and aerogel building insulation blanket materials are becoming more prevalent.

For many years, inexpensive energy made it possible to design buildings without regard for energy performance. The global movement toward sustainability has led to tightening regulations often restricting design freedom.

Local, national, and global organizations continue to develop codes that mandate increased thermal performance in insulation and, in turn, reductions in energy consumption. Construction in the United States can be subject not only to prevailing building codes, but also standards such as American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1, Energy Standard for Buildings Except Low-rise Residential Buildings, with increasing pressure to comply with voluntary standards and certifications such as the United States Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) v4. Other drivers include:

  • 2012 International Energy Conservation Code (IECC);
  • Living Building Challenge;
  • growing demand for net-zero buildings; and
  • American Institute of Architects’ (AIA’s) 2030 Challenge.

From a design standpoint, simply increasing the amount of conventional insulation used in a building is neither practical nor aesthetically pleasing. New insulation technologies provide the performance advantages necessary to achieve effective building envelope insulation without sacrificing design aesthetics.

Integrated use of high-performance insulation in the curtain wall spandrel, in Calgary, Alberta, enables high window-to-wall-ratio designs that meet energy codes. [CREDIT] Photo courtesy BIG

Integrated use of high-performance insulation in the curtain wall spandrel, in Calgary, Alberta, enables high window-to-wall-ratio designs that meet energy codes. Photo courtesy BIG

Thermal performance of commercial insulation materials. [CREDIT] Images courtesy Dow Corning Corporation

Thermal performance of commercial insulation materials. Images courtesy Dow Corning Corporation

 

 

Balancing design trends with energy performance
Cognizant of the need for energy performance, architects are put in a challenging position. Designers are pressured by current building trends to include as much glazing and vision area as possible for optimal aesthetic value, striving to create iconic buildings of aluminum and steel with floor-to-ceiling glass. However, this rise in the use of glass means increasing energy performance can be challenging.

Unfortunately, extensive use of vision glazing is generally lower in thermal performance. To achieve an overall desired level of exterior wall performance, architects and designers must depend on the non-vision spandrel sections.

Used on the façades of commercial buildings, these opaque spandrel sections—typically composed of metal, stone, or glass panels—are used to conceal the floor lines. The spandrels are often designed to visually blend so closely with the vision glass they are not even perceptible, creating the effect of a uniform, all-glass building (Figure 1). They also are manufactured in various colors and designs, adding additional visual interest to the curtain wall’s appearance.

More importantly, the spandrels can be highly insulated to contribute to the façade’s overall thermal performance. Leveraging technical design opportunities in the spandrel sections allows designers to maximize the vision area and still meet prescribed thermal performance requirements of energy conservation codes, such as ASHRAE 90.1 and IECC.

Mineral wool requires eight to 10 times the thickness to provide the equivalent insulation value of a vacuum insulation panel (VIP).

Mineral wool requires eight to 10 times the thickness to provide the equivalent insulation value of a vacuum insulation panel (VIP).

Traditionally, spandrel areas need to be supplemented with an additional layer of thick mineral wool or similar conventional insulation to achieve the necessary thermal value. However, in higher climate zones, such as Climate Zones 4 and 5, this approach may require additional space within the curtain wall to accommodate the required thickness to achieve thermal performance targets. Thin-profile high-performance insulation technologies can solve these challenges.

Beyond the building’s outward aesthetics, architects are also facing the challenge of mitigating uncontrolled thermal losses due to thermal bridging across the building envelope. These heat losses typically occur at transitional conditions in building envelopes, such as:

  • exposed slab edges;
  • where glazing systems meet cavity wall components;
  • where below-grade and above-grade systems meet; and
  • where parapets meet roofs.

Building codes and regulations now require mitigation of thermal bridging conditions. They can make it especially challenging for architects to retrofit existing designs with insulation solutions meeting both performance requirements and available space limitations.

New applications for high-performance insulation technologies
Architects and designers have additional flexibility to respond to insulation performance challenges with high-performance insulation technologies, such as vacuum insulation panels. VIPs can be integrated into architectural insulation modules to enable whole-wall envelope thermal performance improvements; aerogel building insulation blankets can also be included to help address detail-specific thermal bridging issues. These materials not only demonstrate a step-change in thermal performance compared to traditional insulation materials, but also enable designs using current construction techniques to meet demands of the next generation of thermal requirements.

Figure 2 shows the thermal resistance (i.e. RSI, R-value) which is typically expressed as R-value per inch, of various insulation products, including materials typically found on a job site such as expanded polystyrene (EPS), mineral wool, and polyisocyanurate (polyiso). As demonstrated by Figure 2, the change to higher-performing materials is significant, with silica-fume-based vacuum insulation panels as high as RSI 5.63 to RSI 6.16 per 25 mm (R-32 to R-35 per inch) and the aerogel building insulation blanket at RSI 1.73 per 25 mm (R-9.8 per inch).

Composition of vacuum insulation panel.

Composition of vacuum insulation panel.

Thin-profile vacuum insulation panels
Vacuum insulation panel technology provides designers with new options. Offering insulation in a slender profile, a VIP’s thermal performance gives it the equivalency of eight to 10 times the thickness of mineral wool insulation typically used on a construction site (Figure 3).1

Forms of vacuum insulation were invented more than a century ago, and interest has grown over the past several decades in applications where constrained space and weight benefits justify the higher cost, such as commercial applications, as well as in ‘cold-chain’ applications, such as insulated shipping and transport containers. Now, the technology is finding its place in commercial façade insulation applications.

VIP construction (Figure 4) is based on a pressed fumed silica core, which is formed and heated to drive out the moisture. It is then inserted into a handling bag (i.e. core bag) and then into a multilayer, aluminized bag. As that bag is put under full vacuum, its edges are heat-sealed. When the vacuum is released, a full vacuum is contained within the bag. With the vacuum, all the atmospheric gases around the fumed silica are removed, therefore eliminating convective heat transfer from the gases within. With the full vacuum, the unit achieves the initial RSI 5.6 to RSI 6.2 per 25 mm (R-32 to R-35 per inch) center-of-panel (COP) performance. Without the vacuum, the material provides about RSI 1.4 per 25 mm (R-8 per inch), which is approximately twice as good as typical foam insulation—so even if the material loses its vacuum, it continues to provide good insulation performance.2

VIP offers many advantages. It has low nominal thermal conductivity—approximately 4 mW/mK at COP. The metalized bag around the panel is inherently moisture-resistant. The fumed silica core is an ash created by burning a silane. Essentially, the material has already been burned, providing a high degree of fire resistance. The VIP’s thin profile can also allow it to solve various problems; for example, increasing thermal performance requirements not being met by conventional means, or maintaining thermal performance requirements while allowing for increased vision area.

VIP is a pre-engineered product and must be customized by the manufacturer or packaged as part of a system; it cannot be cut to size onsite, as cutting or puncturing the material would cause a vacuum loss and resulting loss of thermal performance.

Cutaway view of architectural insulation modules incorporating VIP technology.

Cutaway view of architectural insulation modules incorporating VIP technology.

Architectural insulation modules are available in various finishes to meet aesthetic requirements.

Architectural insulation modules are available in various finishes to meet aesthetic requirements.

 

AIMs–integrated curtain wall application of VIP
The façades of modern glass curtain walls typify an ideal application for vacuum insulation panel technology. Curtain walls create the iconic artwork and unique character of a building. The ability to maintain a slim façade with a high thermal performance gives the architect the design freedom to maximize the wall’s vision area and/or thermal performance while still meeting local building codes.

For curtain wall applications, VIP technology is provided in an integrated façade module known as an architectural insulation module, which combines a VIP with a protective architectural finish (Figure 5). The module has a back pane of a rigid structural panel material, joined with a warm edge spacer (as used in the insulating glass industry) around the perimeter. VIP is inserted into the space—which typically is the air space in an insulating glass unit—and covered with a finished panel on the front. Modules are available in various architectural options, including opaque, metal, and glass with ceramic frit or ceramic frit patterns (Figure 6).

Performance of architectural insulation modules of various thicknesses.

Performance of architectural insulation modules of various thicknesses.

Modeling and guarded hot-box testing demonstrates the performance characteristics of architectural insulation modules technology (Figure 7). A 25-mm (1-in.) thick unit modeled with a two-dimensional finite element thermal analysis software package, resulting in an effective RSI 1.90 (R-10.84) and a COP value of RSI 3.84 (R-21.8).

A 50-mm (2-in.) thick unit is tested with ASTM C1363, Standard Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus. Figure 7 shows actual test results of a 50-mm thick structural panel, which includes a 6-mm (1/4-in.) piece of glass on each side and a 38-mm (1.5 in.) VIP in the interspace, sized at 1.5 x 1.5 m (5 x 5 ft), indicating an effective RSI of 3.4 (R-19.05). The effective R-value is lower due to factors including heat losses around the insulating glass spacer assembly.

In addition to demonstrating superior thermal performance, the AIM is designed to meet the physical demands of commercial façade applications, withstanding typical windloads and meeting structural requirements. Constructed to standard or custom spandrel size specifications, the modules require no special installation techniques, eliminating need for specialized installer training.

Effect of VIP on U-value and window-to-wall ratio performance.

Effect of VIP on U-value and window-to-wall ratio performance.

Whole-wall insulation performance
Designing a slim façade with a higher percentage of vision requires the lowest possible U-values for spandrel areas to augment thermal performance characteristics. VIP-integrated façade modules enable additional vision area while still complying with thermal performance requirements, improving the curtain wall’s overall whole-wall performance.

When this technology is applied to a building design, it increases thermal performance by maintaining the same window-to-wall ratio, but its replacing of traditional insulation with architectural insulation modules, increases overall curtain wall thermal performance (Figure 8, Arrow 1).

Further, it increases design freedom as architects gain ability to potentially increase window-to-wall target ratios substantially, without compromising on the insulation value of the curtain wall configuration (Figure 8, Arrow 2X).

Blanket insulation
Like the vacuum insulation technology, aerogel is not a new concept, but it has been optimized for the next generation of building challenges. Invented in the 1930s, the material is composed of 95 to 99 percent air, making it one of the lightest materials. Its nanoporous structure minimizes thermal transport, giving it low thermal conductivity. It has been used in various applications, especially aerospace, but with tightening environmental requirements and increasingly complex building designs, aerogel insulation has now found a new niche providing thermal protection in space-restricted areas.

An aerogel building insulation blanket is made from synthetically produced amorphous silica gel. It features a small particle size, with the diameter of the spaces between aerogel particles similar to the fumed silica in the vacuum insulation panels. Manufacturing this material in a blanket form (Figure 9) creates a usable, flexible, construction-friendly material that can be cut-to-size onsite and applied to reduce the thermal bridging at specific locations in a building envelope assembly. Aerogel building insulation blankets are highly resistant to flame, with an ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials, Class A fire rating (flame spread index 5, smoke developed index 10).

Flexible, highly insulating aerogel building insulation blanket.

Flexible, highly insulating aerogel building insulation blanket.

Linear transmittance reductions with aerogel building insulation blankets.

Linear transmittance reductions with aerogel building insulation blankets.

 

Minimizing thermal bridging
Updating architectural details to address thermal bridging concerns has become more common due to increasingly explicit and stringent building codes. The availability of a thin, flexible insulation material reduces the need to make trade-offs in design to meet codes and regulations, and it eliminates bulky or messy insulation from those tight areas of building designs.

Based on ASHRAE Research Project (RP) 1365, Thermal Performance of Building Envelope Details for Mid- and High-rise Buildings, three common construction details were modeled to demonstrate the effect of using aerogel building insulation blankets to minimize thermal bridging. These models are:

  • curtain wall-at-grade detail with the aerogel building insulation blanket applied from the neck of the curtain wall to the below-grade rigid insulation, resulting in a reduction in linear thermal transmittance approaching 25 percent;
  • curtain wall jamb at the exterior and interior insulated steel stud assembly with the aerogel building insulation blanket applied around the adjacent steel stud and at the wall-to-curtain wall transition, resulting in a reduction in linear thermal transmittance approaching 70 percent; and
  • rehabilitated window-wall system with the aerogel building insulation blanket at the slab edge and around vertical and horizontal glazing mullions, resulting in a reduction in linear thermal transmittance approaching 53 percent.

Lineal transmittance values can readily be incorporated into thermal models. This eliminates the guesswork and improves the predictability of the heat loss due to thermal bridging at those locations. (See Figure 10.)

Additionally, two whole-building energy models were created to demonstrate the effect of using aerogel building insulation blanket with conventional and higher-performance assemblies to minimize thermal bridging:

  • for a building with the glazing system covering 100 percent of the façade area, addition of the an aerogel blanket, with conventional assemblies resulted in a 3.56 percent energy savings;3 and
  • for a façade with curtain wall glazing and a steel stud wall assembly, addition of the aerogel blanket and higher-performing assemblies resulted in a 6.78 percent energy savings.4 (See Figure 11)
Annual heating energy savings for Chicago climate.

Annual heating energy savings for Chicago climate.

Conclusion
Vacuum insulation panels, architectural insulation modules, and aerogel building insulation blankets have been introduced in a range of construction projects in the United States and Europe, with positive response.

In an age of increasingly dramatic building design, architects can take comfort in knowing design does not have to take a backseat to performance and energy efficiency issues in current designs can often be addressed with innovative application of high-performance insulation materials.

Notes
1 For more information, see ASHRAE Fundamentals Handbook 2009. (back to top)
2 Visit Vacuum Insulation: Panel Properties and Building Applications at www.ecbcs.org/docs/Annex_39_Report_Summary_Subtask-A-B.pdf. (back to top)

Stanley Yee, LEED AP, is a façade design and construction specialist for Dow Corning High Performance Building Solutions. He joined the company in 2012 with nearly 20 years of experience in the building enclosure industry, working with curtain wall contracting, façade consulting, and enclosure detailing specialists both nationally and internationally. Yee earned a bachelor of engineering degree from Concordia University (Montréal, Québec). An active member of several industry organizations, he is an elected officer of the Board of Directors for the Glass Association of North America (GANA), representing the Energy Division. He can be contacted via e-mail at stanley.yee@dowcorning.com.

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Maintaining Montana’s Mechanical Insulation: Energy appraisal of commercial buildings

All images courtesy National Insulation Association

All images courtesy National Insulation Association

by Christopher P. Crall, PE, and Ronald L. King

In 2010, a mechanical insulation energy appraisal was conducted on various facilities around Helena, Montana. The objective was to determine the energy, cost, and emission reduction opportunities available through repair, replacement, and/or maintenance of mechanical insulation systems in 25 pre-selected facilities.1

The Mechanical Insulation Assessment Pilot Program was part of the data-gathering goal of the Mechanical Insulation Education and Awareness Campaign (MIC). Executed under the U.S. Department of Energy’s (DOE’s) Advanced Manufacturing Office in conjunction with the National Insulation Association (NIA) and its alliance partners, MIC seeks to raise awareness of the energy efficiency, emission reduction, economic stimulus, and other benefits of the material in the industrial and commercial markets.

The potential of mechanical insulation—thermal protection for piping, equipment, and other devices—to play a significant role in reducing energy intensity is immense. Unfortunately, the lack of sufficient data to support its energy efficiency potential, combined with a deficient understanding of what mechanical insulation is and how it can be used, impedes policy- and decision-makers in developing supportable cases for increased use and maintenance of the mechanical insulation.

This is an example of an uninsulated end cap on steam header.

This is an example of an uninsulated end cap on steam header.

The study
The overall approach of the program was to assemble a team of insulation professionals to conduct an appraisal of State of Montana facilities in the Helena area. The assessment team, with assistance from state personnel, performed tasks including:

  • identifying opportunities to improve insulation in the mechanical rooms visited;
  • estimate costs to improve or upgrade the insulation systems;
  • estimate savings (in dekatherms, dollars, and carbon dioxide [CO2] emissions) associated with the insulation upgrades, and calculate resulting payback period and return on investment (ROI).

The list of candidate buildings in the area was developed and prioritized based on the energy-saving potential from mechanical insulation. Based on the program, buildings with steam and/or hydronic heating systems were included, while those with forced air furnaces were not. The 25 facilities visited ranged from office buildings, assembly facilities, and dormitories to maintenance facilities and museums—representing roughly 1.3 million sf (120,774 m2).(As the original research focused solely on imperial measurements, conversions to metric throughout this article are approximate.)

The study’s scope was limited to the assessment of mechanical insulation on piping and equipment in mechanical rooms. Opportunities for repair and replacement of insulation on piping and ductwork within the building itself were not considered. This study should not be considered an energy audit of the buildings visited. Energy conservation opportunities related to building envelope insulation or sealing, lighting, controls, ventilation, and equipment maintenance were also outside the study’s scope.

For each mechanical room, an insulation summary identifying items where the material was missing or had sustained significant damage was developed. The team also identified the thicknesses required to bring the insulation level up to the existing level. No attempt was made to ‘optimize’ the level of insulation or to identify whether the standing level would meet or exceed those required by local building codes. Also, no assessment was made of the existing insulation’s efficiency. Additional savings may be possible by upgrading the level, but these savings would be minimal compared with insulating the uninsulated or damaged items identified.

These uninsulated unions and valve bonnets are used in heating hot water lines.

These uninsulated unions and valve bonnets are used in heating hot water lines.

During the field visits, additional information was collected about the energy systems in each mechanical room to enable the estimation of energy savings, including:

  • the mechanical room’s location within the building;
  • operating temperatures;
  • estimated hours of operation;
  • estimated efficiency of the equipment; and
  • general control strategies.

Budget-type cost estimates were also developed based on the summary information on a facility-by-facility basis.

Assessment findings
Each of the facilities chosen for analysis had at least a few items requiring insulation. The smallest number of individual items identified in a building was 14. It included:

  • one 12-ft (3.6-m) long, 2-in. (51-mm) copper tube;
  • one 3-ft (0.9-m) long, 3/4-in. (19-mm) copper tube;
  • six 2-in. 90-degree elbows;
  • five 2-in. ball valves; and
  • one 3/4-in. ball valve.

The largest concentration of items was in a boiler plant facility that provides central steam and domestic hot water to four buildings in the Capitol Complex. Approximately 400 individual items were identified in this facility (including tunnels), and savings due to insulation provided an estimated payback of four years.

Overall, approximately 3500 items were identified. Estimated total savings were approximately 6 billion Btus per year, with an estimated payback of four years and an annualized rate of return of 24 percent. These projected savings are primarily in natural gas use and represent roughly eight percent of the total analyzed facility’s natural gas consumption.

As expected, some items identified were large, such as the uninsulated flanged end cap on a large, low-pressure steam header shown in Figure 1. The majority, however, were relatively minor like the uninsulated unions and valve bonnets on the hot-water heating lines shown in Figure 2. While the savings from any single item is small, the total savings from thousands of small items is significant.

Figure 3 summarizes the overall results of the appraisal, sorted in order of decreasing energy savings. Building energy usage information was derived from data provided by the State of Montana and, in most cases, is the average consumption over a four-year period (i.e. 2007 to 2010).2

Energy Use Intensity (EUI)—measured in units of kBtu/sf/yr—is the annual building site energy consumption (electrical and natural gas) per square foot of gross building area. Available EUIs for the Helena buildings range from a high of 193 to a low of 47.3 The unweighted average EUI for these buildings is roughly 92 kBtu/sf/yr. For reference, the U.S. Energy Information Agency’s (EIA’s) 2003 Commercial Building Energy Consumption Survey for this climate zone lists average EUI values for offices at 92 and assembly buildings at 102.

Numerous key assumptions were required to develop the energy savings estimates, including the operating hours of the mechanical systems involved. Heating systems are assumed to operate for eight months during the winter, or 5840 hours per year. Additional assumptions include an operating temperature of 80 F (27 C) and ambient conditions inside the mechanical rooms with 1-mph (1.6-km/h) wind speed.

The results of the appraisal are summarized in this chart.

The results of the appraisal are summarized in this chart.

The total estimated savings are approximately 6 billion Btu/yr. The weighted average savings are 4.6 kBtu/sf/yr. This represents 8.2 percent of natural gas usage in the facilities studied. In most cases, the insulation opportunities identified will reduce natural gas consumption. However, a few of the buildings have electrically heated domestic hot-water systems—in those buildings, a small portion of the energy savings due to mechanical insulation shows up as electrical energy savings. These electrical energy savings are expressed as dekatherms and included in the estimates.

The savings estimates in Figure 3 are converted to the associated reductions in CO2 emissions (annual metric tonnes) and then to financial savings ($/sf/yr).

Insulation cost estimates were prepared on a facility-by-facility basis using the summaries developed during site visits. The estimates assume various insulation systems depending on the application. The primary insulation system used in the estimates was fiberglass pipe insulation with all service jacket and removable/replaceable flexible insulation covers.

A building’s boiler installation is shown here.

A building’s boiler installation is shown here.

Column 12 in Figure 3 shows the estimated payback period of the insulation project in years, while column 13 gives the annualized rate of return (assuming a 20-year life and no fuel cost escalation4). The estimated payback periods range from 1.8 years to 10.7 years. Corresponding annualized returns range from seven to 54 percent.

As might be expected, the steam-heated facilities generally showed shorter payback periods. Steam supply piping operates at roughly 230 F (110 C) during the heating season, while hot-water supply temperatures are normally reset in a range from 120 to 180 F (49 to 82 C) based on outdoor conditions. Insulating steam systems will therefore not only exhibit greater energy savings, but also quicker payback.

The variation in financial returns is not unexpected. All the buildings inspected had mechanical insulation on their steam and hot water lines, although some systems were in better shape than others. Several had been recently upgraded to high-efficiency condensing boilers with well-insulated piping (Figure 4). While numerous small items were identified in each of these facilities, the ‘low-hanging fruit’ had been gathered.

Significance of results
The results of this study demonstrate there are numerous opportunities for improving the mechanical insulation application in steam- and hydronic-heated buildings. One question prompted by the appraisal is, ‘Why are there so many pieces of missing insulation?’

In many locations, it was obvious a maintenance task had required removal of the insulation, which was simply not replaced after the maintenance was completed. This was observed in several locations where a domestic hot-water (DHW) storage tank had been removed and replaced with a newer tank, and piping connections to the tank were left uninsulated. It is possible the personnel performing the work did not have the materials or proper training to complete the job.

This uninsulated condensate tank was installed in a corrections facility.

This uninsulated condensate tank was installed in a corrections facility.

In some areas, either mechanical damage or leaks had occurred and the damaged insulation had not been replaced. More common, however, were items that had never been insulated. For buildings and systems designed and built when energy was less expensive, the ‘extent of insulation’ was not nearly as complete as it is today. Items routinely left uninsulated include:

  • pipe unions;
  • strainers;
  • steam traps;
  • condensate tanks;
  • expansion joints;
  • valves;
  • flanged joints;
  • pumps; and
  • tanks.

The DHW systems in the buildings illustrated the interactions often present in energy conservation projects. Numerous buildings contained newer high-efficiency DHW storage tanks. Some buildings, however, used older conventional-style gas-fired water heaters. For older DHW tanks, the addition of a 1.5-in. (38-mm) thick tank blanket to minimize heat loss was analyzed. These DHW tanks typically operate year-round (i.e. 8760 hours). For a typical 24 by 60-in. (610 by 1524-mm) tank, energy savings can be approximately $30 annually. These savings were included in the analysis where applicable. Depending on the age of the DHW tank, it may be more reasonable to consider replacing these tanks with high-efficiency units. This alternative (and mutually exclusive) option was not investigated in this study.

A related interaction issue concerns the DHW circulating systems. Most of the buildings studied use circulating pumps in the DHW loops. These pumps minimize city water consumption since occupants have hot water at fixtures on demand, rather than waiting for hot water. Some facilities have been fitted with timers to limit the circulating pumps operating hours—and the associated heat loss from DHW piping—to occupied hours.

In other buildings, the circulating pumps continuously run. For these facilities, the insulation replacement items are appealing because savings are directly proportional to operating hours. The alternative option of installing a timer to limit hours of operation would reduce the savings from insulation. The two options, however, are not mutually exclusive, and installation of timers should be considered in addition to replacing any missing insulation in the DHW loop.

A condensate piping assembly is seen here.

A condensate piping assembly is seen here.

Extrapolating the findings statewide
One of the program’s objectives was to use the results to estimate possible savings if the study were expanded to cover similar state-owned buildings. The State of Montana has an inventory of approximately 2000 different types of buildings, from roadside rest facilities and historical village gift shops to prisons and university football stadiums. Many of these facilities are small, seasonal, and with specialized use and/or limited occupancy. As the study’s results do not apply to all facilities, extrapolation to every state building is not accurate. However, projections to similar state-owned facilities are possible and may be useful.

The initial step toward that objective was to review a list of state buildings considered potential candidates for inclusion in mechanical insulation upgrade projects. The information provided included:

  • building designation and location;
  • year built;
  • occupancy code;
  • gross area (in square feet);
  • number of stories; and
  • number of full-time employees.

The list contained a total of 142 buildings with a total gross area of 2.35 million sf (218,322 m2).

The pilot study of Helena buildings covered several of the larger state buildings, representing a significant percentage of the total. Overall, approximately 55 percent of the square footage identified on the candidate list was included in the study discussed. As a first-order estimate, the energy savings from the Helena study can be prorated based on building area. Annual energy savings from the 25 facilities analyzed averaged 4.6 kBtu/sf/yr, which is about $0.043/sf/yr. If these savings were prorated to the statewide candidate list (i.e. 2.35 million sf [21,8322 m2]), they would total 10,800 DKT, or $101,000, annually.

However, additional analysis could refine this estimate. For example, it was determined steam- and hydronic-heated systems will have more opportunities for mechanical insulation than their forced-air counterparts. Additionally, some candidate buildings have already been addressed. More information about the building inventory statewide would allow a more precise estimate, but an order-of-magnitude statewide savings of 10 billion Btus—eight percent savings annually—is not unreasonable. Installation costs would be similar, so annualized returns of 24 percent could be achieved.

This is an uninsulated steam valve.

This is an uninsulated steam valve.

Conclusion
Approximately 3500 items were identified in 25 buildings and 56 mechanical rooms in the pilot program, with estimated annual energy savings of approximately 6 billion Btu per year, a resulting overall payback period of four years, and an annualized rate of return of 24 percent. Associated reductions in CO2 emissions are estimated at 300 metric tonnes per year.

While the savings from a single item is small, the aggregated total savings from thousands of small items is significant. The appraisal results confirm the value of addressing missing, damaged, or uninsulated areas. The payback period and internal rate of return are based on actual operating conditions, 80-F (27-C) ambient temperature, service temperature, and hours of operation (in many cases, less than half a year).

The results tell an impressive story for the maintenance of mechanical insulation in commercial building applications. The findings confirm the energy savings, emission reduction, and financial benefits of looking at mechanical insulation differently.

Notes
1 An earlier version of this article appeared in the May 2011 issue of the National Insulation Association’s Insulation Outlook publication. (back to top)
2 Annual Heating Degree Days over this four-year period averaged 7751, or about 0.9 percent higher than the long-term average for Helena. Visit www.insulationoutlook.com/io/article.cfm?id=IO110501#fn1. (back to top)
3 For site EUI calculations, 1 kWh of electrical energy is 3412 Btu and 1 dekatherm is 1,000,000 Btu. Electrical consumption at the Montana Law Enforcement Academy Complex is billed from a master meter, so EUI could not be broken out for the portion of that campus analyzed. (back to top)
4 Energy costs are volatile and notoriously difficult to predict. While long-term energy costs are expected to increase, recent natural gas costs have been falling. A fuel cost escalation rate of 0 percent seems reasonable for this analysis. If a three percent annual fuel cost escalation rate was assumed, annualized returns would increase by about three percent. For example, the 27 percent return estimated for the Capitol building would increase to 30 percent if a three percent/yr fuel cost escalation rate was used. (back to top)

Christopher P. Crall, PE, is a mechanical engineer with experience in thermal insulation and energy usage in commercial buildings and industrial applications. He is currently providing consulting services in the areas of building energy standards, energy analysis, heat and moisture transport, and mechanical insulation specifications and applications. Crall is an active ASHRAE member and was the primary author of the 2005 ASHRAE Handbook chapter titled “Insulation for Mechanical Systems.” He is also active as a member of the ASTM Committee on Thermal Insulation (C-16). Crall can be reached at ccrall@gmail.com.

Ronald L. King is a past president of the National Insulation Association (NIA), the World Insulation and Acoustic Organization, and the Southwest Insulation Contractors Association. He has been awarded the NIA President’s Award twice. King is a 40-year veteran of the commercial and industrial insulation industry, during which time he held executive management positions at an accessory manufacturer and a specialty insulation contractor. He recently retired as the chairman, CEO and president of a large national insulation distributor/fabricator and is currently a consultant and advisor. King can be contacted via e-mail at ronkingrlk@aol.com.