WHAT IS A VACUUM INSULATION PANEL (VIP)? The construction of VIPs is based on the principle of vacuum technology, invented by British scientist James Dewar in 1892. VIPs are made with open porous core materials enclosed in an impermeable gas barrier (Figure 1) and have three major components: 1) open porous core material that imparts mechanical strength and thermal insulating capacity, 2) gas barrier/ facer foil that provides the air- and vapor-tight enclosure for the core material, and 3) getter and desiccant inside the core material that help extend the service life by adsorbing residual or permeating atmospheric gases or water vapor in the barrier enclosure. BACKGROUND AND SIGNIFICANCE Reduction of energy consumption in every aspect of our daily lives is considered to be the key to tackling the issues related to global warming and its adverse effects on the environment. Buildings consume up to 40% of our total national energy requirements, and thermal insulation is a key component that determines the energy efficiency of the built environment. Recent upgrades of energy codes (e.g., NECB 2011, IECC 2012, and ASHRAE 2013) have recommended higher levels of insulation in building envelopes. However, addition of more traditional insulation in new or existing roofs and walls is impractical for various reasons such as very thick layers of insulation increasing the thickness of the building envelopes beyond current practices, loss of usable space, etc. (Mukhopadhyaya et al., 2011). These issues have provided a fresh impetus to the search for high-performance thermal insulation for building envelope construction. Among the various nonconventional insulations being introduced to the construction industry as the next-generation thermal insulation, VIPs appear to be one of the most promising insulation materials with the highest thermal insulating capacity (up to ten times more thermally efficient than conventional thermal insulation materials; see Figure 2). In North America and throughout the world, the potential to apply A u g u s t 2 0 1 4 I n t e r f a c e • 1 1 Figure 1 – Vacuum insulation panel (left) and schematic construction of VIP (right). Figure 2 – R-value of VIP compared with other insulation materials. 1 2 • I n t e r f a c e A u g u s t 2 0 1 4 VIPs in building envelope construction is enormous, and VIPs can play a major role in existing and new buildings to meet the higher insulation requirements of the newly introduced energy codes. However, the acceptance of VIPs in the construction industry is critically dependent on cost, long-term performance, and availability of best-practice guidelines. The expensive core material (e.g., precipitated silica or fumed silica) is one of the main reasons behind the higher cost of VIPs, which offer a satisfactory long-term service life in building envelope applications. To overcome this cost barrier to mass application of VIPs in the building industry, researchers at the National Research Council of Canada – Construction Portfolio (NRC Construction) have developed a low-cost, fiber-powder composite core material for VIP (Mukhopadhyaya et al., 2008, 2014). Similar ongoing efforts have been reported around the world to introduce glass fiber and other innovative core materials for VIPs (Dia et al., 2014; Alam et al., 2014). The long-term performance of VIP is governed by two distinct phenomena (Figure 3): 1) aging and 2) durability. Aging is considered to be a natural phenomenon for VIPs, but unknowns are the nature and rate of aging. On the other hand, durability is an issue that is related to manufacturing, quality control, handling, and maintenance of VIPs. Finally, development of best-practice guidelines is one of the most important steps for creating broader market access for VIPs in the building construction industry. Several real-life examples of VIPinsulated building envelope systems are provided in literature (Binz et al., 2005; Mukhopadhyaya, 2011; Brunner and Ghazi Wakili, 2013); however, development of technical best-practice guidelines is still a work in progress at best. The following paragraphs introduce readers to the construction of VIPs, heat transfer fundamentals related to their performance, advantages and challenges, and observations from two real-life field constructions. The authors hope that dissemination of the technology behind VIPs and their performance record will stimulate the construction industry in general and the roofing community in particular to exploit the historic opportunity arising from the newly introduced building energy codes and to integrate VIPs in the mass construction market of North America and the rest of the world. FUNDAMENTALS OF HIGHER R-VALUE OF VIP A few eyebrows may be raised over the high R-value of VIPs, which can reach R-60/in. or higher. Considering the fact that the most efficient foam insulation is about R-6/in., and the most efficient aerogel- based thermal insulation has about R-10/in. thermal resistance, it is important to understand the fundamentals of heat transfer mechanisms that make the much higher R-value of VIP a credible reality. There are three basic heat transfer mechanisms that control the insulating capacity of conventional thermal insulation materials. These are: 1) conduction (solid Figure 3 – Aging and degradation of VIPs. Figure 4 – Heat transfer mechanisms through insulation materials. conduction and air conduction), 2) convection, and 3) radiation. It should be noted that air conduction of heat transfer happens in still air due to random movement of air particles and collisions among them. The solid conduction and radiation components are functionally related to the density of the insulation materials (Figure 4), and preventing air movement through air space inside the insulation can eliminate the convective heat flow phenomenon almost entirely. However, air conduction is an independent component and offers a significant opportunity to develop high-performance thermal insulation materials by effectively reducing this component. REDUCING AIR CONDUCTION IN THERMAL INSULATION The reduction of thermal conduction through air (i.e., air conduction) can be done in three ways: 1. Replacing the air with a gas that has a thermal conductivity less than that of air 2. Reducing the pore size in insulation materials to nanoscale 3. Reducing the air pressure inside the insulation material The first approach listed herein is the key for development of closed-cell foam insulation where gaseous blowing agents with thermal conductivity lower than air replace the air inside the closed cells. The increase of thermal resistance with the decrease of effective pore size of the insulation material is a well-known physical phenomenon, particularly for nano-pore-structured insulation materials (e.g., aerogel). In the third approach—reducing the air pressure inside the insulation material to increase the thermal resistance—the air pressure inside the open porous structure of an insulating material is brought very close to zero (Figure 4), and the resulting insulation product is a VIP. APPLICATION OF VIPS IN BUILDING ENVELOPE CONSTRUCTION: ADVANTAGES AND CHALLENGES VIPs offers a number of advantages and challenges for application in the construction industry. Advantages 1. Higher thermal resistivity than any known thermal insulation used in the construction industry (Figure 1) 2. Reduced thickness of building envelopes/components, providing increased indoor space and optimization of land use 3. Constitutive materials may be recycled after the service life. Challenges 1. VIPS are more expensive than traditional thermal insulations used for building envelope construction, but are becoming more economically attractive as a result of improved research efforts, automation of manufacturing processes, and increased volume of production. 2. Aging of VIPs due to slow permeation of gases/water vapor through gas barriers, and/or off-gassing of core material can be very slow, but is an undeniable reality. Hence, it is very important for designers and engineers to know the long-term thermal A u g u s t 2 0 1 4 I n t e r f a c e • 1 3 At your own pace, on your own time, at your fingertips … Roof Drainage Design Roof System Thermal and Moisture Design Roofing Basics Roofing Technology and Science I Roofing Technology and Science II Rooftop Quality Assurance Wind Design for Low-Slope Roofs – Part I: Understanding ASCE 7-05 Wind Load Calculations for Members Wind Design for Low-Slope Roofs – Part I: Understanding ASCE 7-10 Wind Load Calculations Wind Design for Low-Slope Roofs – Part II: FM Global Guidelines and Best Practice Considerations Online Educational Programs www.rci-e-learning.org performance of VIPs. 3. Durability (or more specifically, the handling of VIPs on the construction site) is a significant concern, considering the fact that any damage in the vacuum system (even a small pinhole) will destroy the thermal insulating capacity of VIPs. 4. In general, VIPs have a highly conductive gas barrier/foil facer, and VIPs are currently available in sizes that are much smaller than traditional thermal insulation boards (e.g., rigid foam or high-density mineral fiberboard). Thermal bridge effect at edges in a VIP system is a justifiable technical concern. 5. As VIPs cannot be drilled or cut on the construction site, unlike traditional insulation materials, special design considerations must be developed to deal with penetrations through roofs and walls. VIPs with predetermined holes are available at a higher price. However, significant progress has been made to address these issues globally, and initiatives are in progress to mitigate the challenges associated with the application of VIPs in the construction industry (Binz et al., 2005; Mukhopadhyaya, 2011; Brunner and Ghazi Wakili, 2013). EXAMPLES OF FIELD APPLICATIONS VIPs in Walls (Ottawa, Ontario) VIPs were installed in a purpose-built test hut (Figure 5) at the NRC1 Construction campus in Ottawa. The indoor environment of the test hut was controlled, and exterior weather data were monitored. The VIPs were installed on an east-facing wall of the test hut. In the test area of the existing wall, three 1150-mm x 750-mm x 12-mm (45-in. x 30-in. x 0.5-in.) VIPs were installed in an edge-overlapped formation (Figure 6). The test area was equipped with temperature, heat flux, and humidity sensors to gather both external and internal data (Figure 6). The performance of VIPs installed in the test hut wall has been monitored since the winter of 2009-2010. The recorded thermal 1 4 • I n t e r f a c e A u g u s t 2 0 1 4 Figure 5 – NRC test hut, Ottawa, Ontario, Canada. Figure 6 – Construction details of VIPs in wall (Ottawa, Ontario, Canada). performance of VIPs under dynamic temperature conditions is shown as a function of time in Figure 7. In general, there appears to be no evident significant thermal performance degradation of VIPs during four years of field exposure. The monitoring of thermal performance of VIPs installed in the test hut will continue. Performance of VIPs on a Roof (Ottawa, Ontario) The in-service low-slope roof was a 15-year-old built-up system on an NRC office building (Figure 8) undergoing reroofing with the new-generation rigid roofing system (Molleti et al., 2011). The crosssectional layout of this new roof comprised a concrete deck, vapor barrier, 75-mm (3-in.) rigid polyisocyanurate (also known as polyiso or iso) insulation, 6-mm (0.25-in.) asphalt cover board, modified-bituminous membrane base sheet, and a modifiedbituminous membrane cap sheet (Figure 9). This was a mod-bit roofing system, and all the roofing components are integrated with solvent-based roofing adhesive. A 1.2-m x 2.4-m (48-in. x 96-in.) iso-VIP composite was installed, replacing one of the 75-mm (3-in.) iso boards. The 75-mm-thick, adhesivebonded composite VIP comprised two layers of 12-mm- (0.5-in.-) thick 450-mm x 560- mm (18-in. x 22-in.) VIP, staggered to minimize the effects of thermal bridging, sandwiched between two layers of 25-mm- (1-in.-) Figure 8 – Reroofed NRC office building. Figure 7 – Thermal performance of VIP during a typical winter month in 2010, 2011, 2012, and 2014. W. R. MEADOWS Waterproofing Solutions For a solution based on your needs, visit wrmeadows.com or call 1-800-342-5976. H8YDR3ALA6STIC © W. R. MEADOWS, INC. 2014 follow us: W. R . M E A D O W S HYDRALASTI C 836 is a cold-applied, solvent-free, single-component waterproofing compound for horizontal surfaces, s u c h a s p o d i um d e c k s a n d planters. HYDRALASTIC 836 cures to a tough, flexible, elastic membrane that i s applicable for use on concrete sur faces , including green concrete. The product has a low VOC content and meets all North American VOC regulations. If your need is a f lexible, VOC-compl iant , waterproofing membrane, choose H Y D R A L A S T I C 8 3 6 from W. R. MEADOWS. WR_Meadows_Hydralastic_RCI-3_Layout 1 6/24/14 3:2 A u g u s t 2 0 1 4 I n t e r f a c e • 1 5 thick iso board on the top and bottom. Figure 10 shows the performance of VIPs in a week of February 2011, 2012, and 2013, respectively. These data clearly indicate that thermal performance of VIP has not gone down in any significant way over the three years of real-life field exposure in a roof construction. SUMMARY The information and discussion presented in this paper can be summarized as follows: • Based on sound principles of the basic physics of heat transfer, it is realistic to expect five to ten times higher R-value/in. from VIPs than from traditional thermal insulation materials used in building envelope construction. • Use of VIPs in energy-efficient building envelope construction is a real 1 6 • I n t e r f a c e A u g u s t 2 0 1 4 Figure 9 – Construction details: VIPs in roof (Ottawa, Ontario, Canada). Figure 10 – Thermal performance of VIPs during a typical winter week in 2011, 2012, and 2013. * Make sure RCI has your current e-mail address. From the RCI home page (rci-online.org), click on the “Member Login” link on the right. To log onto your member account for the first time, click “Create Account” in order to create a user name and password. Do not create a new account, as members already have existing membership records. Under “Personal,” make sure you have not marked “exclude e-mail.” Now relax…it’s coming soon. Check your e-mail inbox* around the 20th of each month. Have you read tems lately? Missing Something? possibility and an attractive proposition for the roofing industry. • Recent upgrades of building energy codes in North America offer an historic opportunity for the construction industry to integrate VIPs in building envelope construction. • Available field performance evaluation results provide encouraging indicators for the long-term thermal performance of VIPs in both roof and wall constructions. • Application of VIPs as highly efficient thermal insulation in building envelope construction is advantageous (e.g., higher thermal resistance, reduced thickness of building components, recyclable, etc.) and challenging (cost, aging, durability, thermal bridge, etc.) at the same time. • Researchers across the world, including those from the National Research Council of Canada, are working with construction industry stakeholders to exploit the advantages and addressing the challenges. REFERENCES 1. M. Alam, H. Singh, S. Brunner, and C. Naziris, “Experimental Characterisation and Evaluation of the Thermo-Physical Properties of Expanded Perlite-Fumed Silica Composite for Effective Vacuum Insulation Panel (VIP) Core,” Energy and Buildings, Vol. 69, February 2014, pp. 442–450. 2. ANSI/ASHRAE/IES Standard 90.1- 2013, Energy Standard for Buildings Except Low-Rise Residential Buildings, ASHRAE, Atlanta, GA. 3. A. Binz, A. Moosmann, G. Steinke, U. Schonhardt, F. Fregnan, H. Simmler, S. Brunner, K. Ghazi Wakili, R. Bundi, U. Heinemann, H. Schwab, H. Cauberg, M. Tenpierik, G. Johannesson, and T. Thorsell, “Vacuum Insulation in the Building Sector – Systems and Applications (Subtask B)” IEA/ECBCS Annex 39, 2005, pp. 1-134. 4. X. Dia, Y. Gao, C. Bao, and S. Ma, “Thermal Insulation Property and Service Life of Vacuum Insulation Panels With Glass Fiber Chopped Strand as Core Materials,” Energy and Buildings, Vol. 73, April 2014, pp. 176–183. 5. S. Brunner and K. Ghazi Wakili (editors), Proceedings of 11th International Vacuum Insulation Symposium (IVIS-XI), Dübendorf, Switzerland, 2013, pp. 1-124. 6. International Energy Conservation Code (IECC), 2012, International Code Council (ICC), Lenexa, KS, U.S. 7. S. Molleti, P. Mukhopadhyaya, A. Baskaran, P. Beaulieu, and G. Sherrer, “Application of Vacuum Insulation Panels in Low-Sloped Commercial Roofing Systems,” Proceedings of the 10th International Vacuum Insulation Symposium (IVIS-X), 2011, p. 10, Ottawa, ON, Canada. 8. P. Mukhopadhyaya (editor), “Vacuum Insulation Panels: Advances in Applications,” Proceedings of 10th International Vacuum Insulation Symposium (IVIS-X), Ottawa, ON, Canada, 2011, pp. 1-218. 9. P. Mukhopadhyaya, K. Kumaran, F. 30th International Convention RCI, Inc. | rci-online.org/international-convention.html | 800-828-1902 and Trade Show March 05-10, 2015 | San Antonio, Texas Grand Hyatt San Antonio | San Antonio Convention Center A u g u s t 2 0 1 4 I n t e r f a c e • 1 7 Ping, and N. Normandin, “Use of Vacuum Insulation Panel in Building Envelope Construction: Advantages and Challenges,” Proceedings of the 13th Canadian Conference on Building Science and Technology (Winnipeg, Manitoba, 2011-05-10), pp. 1-10. 10. P. Mukhopadhyaya, K. Kumaran, N. Normandin, D. van Reenen, and J. Lackey, “High Performance Vacuum Insulation Panel: Development of Alternative Core Materials,” ASCE Journal of Cold Regions Engineering, Vol. 22, No. 4, December 2008. 11. P. Mukhopadhyaya, D. van Reenen, and N. Normandin, “Performance of Vacuum Insulation Panel Constructed with Fiber-Powder Composite as Core Material,” ASTM STP 1574, pp. 1-10, April 2014, ASTM International, West Conshohocken, PA, U.S. 12. National Energy Code of Canada for Buildings (NECB), 2011, National Research Council of Canada, Ottawa, Ontario, Canada. 13. H. Simmler, S. Brunner, U. Heinemann, H. Schwab, K. Kumaran, P. Mukhopadhyaya, D. Quénard, H. Sallée, K. Noller, E. Kücükpinar-Niarchos, C. Stramm, M. Tenpierik, H. Cauberg, and M. Erb, “Study on VIP Components and Panels for Service Life Prediction of VIP in Building Applications,” Subtask A, IEA/ECBCS Annex 39, 2005, pp. 1-157. FOOTNOTE 1) National Research Council of Canada, Ottawa, ON, Canada 1 8 • I n t e r f a c e A u g u s t 2 0 1 4 Phalguni Mukhopadhyaya is a senior research officer at the National Research Council of Canada. His research interests are in energy and moisture performance of building materials and envelope systems. At present, he is working on next-generation thermal insulation materials (VIPs, Aerogel, Bio-foam, etc.) and systems and their integration in the construction industry. Mukhopadhyaya has authored or coauthored about 150 technical publications and reports, coedited two ASTM selected technical papers (STPs 1495 and 1519), and edited one conference’s proceedings (see http://www.ivis2011.org). Phalguni Mukhopadhyaya Sudhakar Molleti is a research officer at the National Research Council of Canada. His work focuses on the wind-induced effects on lowsloped roofing systems. He is currently working on the wind performance of vegetated roof assemblies, energy and durability of PV integrated roofs, and application of vacuum insulation panels in roofing systems. Molleti is a member of the ASTM D08 and CRCA Technical Committees. He received his PhD in engineering from the University of Ottawa (Canada). Sudhakar Molleti David van Reenen has been a technical officer at the National Research Council of Canada for the past 14 years. During this time he has been involved in numerous research projects involving high performance and conventional insulations, building materials, laboratory experiments, field exposures, life-cycle analyses, and hygrothermal simulations. David received his bachelor’s degree in civil engineering from the University of Waterloo (Canada) and his master of science degree in building performance from the Chalmers University (Sweden). David van Reenen Gil Hancock Mende, of Doylestown, PA, died June 14, 2014, at the age of 80. Though few members of RCI knew him, Gil Mende’s contributions to RCI have been considerable. Gil has been an extremely gifted and conscientious proofreader of Interface and RCItems since 2007. In 2008, he researched and wrote RCI’s Silver Anniversary Report, reviewing the first 25 years of our association’s history. Working for RCI was the last stint in a long and varied professional career that included teaching in the U.S., Venezuela, Angola, Afghanistan, Norway, Spain, and the Netherlands, as well as positions as a newspaper reporter, computer programmer, monument salesman, technical writer, teacher of English as a second language, and Braille transcriber for both text and music. Gil Mende with RCI Director of Publications Kris Ammerman at the 2009 RCI convention in Dallas, Texas. Gil Mende 1933-2014
