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Edge loss minimization in vacuum insulation panels: Model verification
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
2006 (English)In: Research In Building Physics And Building Engineering / [ed] Fazio P, Ge H, Rao J, Desmarais G, London, England: TAYLOR & FRANCIS LTD , 2006, 251-256 p.Conference paper, Published paper (Refereed)
Abstract [en]

Vacuum insulation panels have, by design, a thermal bridge at each of the edges of the panel. This paper presents continued work on an edge design that minimizes this effect, a serpentine edge. Numerical modeling as well as laboratory measurements has been done. Results presented here show that this serpentine edge have the potential to reduce the thermal bridge around the edges of a traditional vacuum panel alternatively enable designs with metal foil or thin metal sheet barriers which would allow other core such as glass fibers, open cell polyurethane instead of commonly used fumed silica. Fumed silica or aerogel that have pore-sizes in the nano region might not need stainless steel barriers to reach technical lifetimes of several decades but can still benefit from a sturdier shell. A welded stainless steel envelope helps to create a panel that will withstand handling and other loads in a construction.

Place, publisher, year, edition, pages
London, England: TAYLOR & FRANCIS LTD , 2006. 251-256 p.
Series
Proceedings and Monographs in Engineering, Water and Earth Sciences
Keyword [en]
Bridges, Buildings, Colloids, Electron emission, Engineering research, Glass fibers, Inert gas welding, Metal foil, Polymers, Serpentine, Sheet metal, Silica, Silicate minerals, Stainless steel, Steel, Steel corrosion, Steel metallurgy, Two phase flow, Vacuum
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-6256ISI: 000242847800033Scopus ID: 2-s2.0-56249135581ISBN: 0-415-41675-2 (print)OAI: oai:DiVA.org:kth-6256DiVA: diva2:10922
Conference
3rd International Building Physics Conference Concordia Univ, Montreal, CANADA, AUG 27-31, 2006
Note

QC 20141117

Available from: 2003-10-18 Created: 2003-10-18 Last updated: 2014-11-17Bibliographically approved
In thesis
1. Vacuum insulation in buildings: Means to prolong service life
Open this publication in new window or tab >>Vacuum insulation in buildings: Means to prolong service life
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Vacuum insulation panels, VIPs, constitute a new insulation material, 6 to 8 times better than traditional insulation materials, which utilizes the positive influence vacuum has on the thermal properties of certain materials. A VIP is a composite with a flat core enclosed by an envelope preventing the core to fill with gas. The vacuum in the core is vital to reach thermal conductivities down to 0,0035 W/(m K), if the vacuum is lost the panel has reached the end of its service life time. Metal sheets would the preferred material to create an impermeable envelope but would creates a large thermal bridge at the edges of a panel when it folds over the edges of the panel.

A serpentine edge has been proposed in order to deal with this large thermal bridge. This serpentine edge has been evaluated first as a numeric model in software and then by measuring on a prototype edge element in a hot and cold plate instrument. Measured temperatures were used to validate the numerical model. Results show that a serpentine edge can greatly reduce the thermal bridge if designed correctly.

Another direction taken in the development of the VIP barrier is to use very thin metal layers, metallization layer or coating, incorporated into multi layered polymer composite film. This creates barrier films with very good barrier properties and only small thermal bridges. The modeling of gas flux through films with more than one coating has only just started. Existing models for flux through multi coated films all assume that flux is only taking place through defects in the coating layers, that all defects are of the same size and that all defects are positioned in square lattices. The model discussed herein use the same assumption of flux through pinholes only but it does take defect sizes and positions into account. Barrier film, from a regular vacuum insulation panel, with double coatings has been evaluated in light microscopy to characterize the defects in each of the coatings. The data found have been fed into the model and the results comply well with reported permeabilities of similar barrier films.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. x, 43 p.
Series
Meddelande. Institutionen för byggvetenskap, ISSN 1651-5563 ; 198
Keyword
vacuum insulation, thermal bridge, serpentine edge, coated film
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-4149 (URN)91-7178-470-5 (ISBN)
Presentation
2006-11-02, Fyslab, KTH, Brinellvägen 34, Stockholm, 11:00
Opponent
Supervisors
Note
QC 20101125Available from: 2003-10-18 Created: 2003-10-18 Last updated: 2010-11-25Bibliographically approved
2. Advances in Thermal Insulation: Vacuum Insulation Panels and Thermal Efficiency to Reduce Energy Usage in Buildings
Open this publication in new window or tab >>Advances in Thermal Insulation: Vacuum Insulation Panels and Thermal Efficiency to Reduce Energy Usage in Buildings
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

We are coming to realize that there is an urgent need to reduce energy usage in buildings and it has to be done in a sustainable way. This thesis focuses on the performance of the building envelope; more precisely thermal performance of walls and super insulation material in the form of vacuum insulation. However, the building envelope is just one part of the whole building system, and super insulators have one major flaw: they are easily adversely affected by other problems in the built environment. 

Vacuum Insulation Panels are one fresh addition to the arsenal of insulation materials available to the building industry. They are composite material with a core and an enclosure which, as a composite, can reach thermal conductivities as low as 0.004 W/(mK). However, the exceptional performance relies on the barrier material preventing gas permeation, maintaining a near vacuum into the core and a minimized thermal bridge effect from the wrapping of barrier material round the edge of a panel.

A serpentine edge is proposed to decrease the heat loss at the edge. Modeling and testing shows a reduction of 60% if a reasonable serpentine edge is used. A diffusion model of permeation through multilayered barrier films with metallization coatings was developed to predict ultimate service life. The model combines numerical calculations with analytical field theory allowing for more precise determination than current models. The results using the proposed model indicate that it is possible to manufacture panels with lifetimes exceeding 50 years with existing manufacturing.

Switching from the component scale to the building scale; an approach of integrated testing and modeling is proposed. Four wall types have been tested in a large range of environments with the aim to assess the hygrothermal nature and significance of thermal bridges and air leakages. The test procedure was also examined as a means for a more representative performance indicator than R-value (in USA). The procedure incorporates specific steps exposing the wall to different climate conditions, ranging from cold and dry to hot and humid, with and without a pressure gradient. This study showed that air infiltration alone might decrease the thermal resistance of a residential wall by 15%, more for industrial walls.

Results from the research underpin a discussion concerning the importance of a holistic approach to building design if we are to meet the challenge of energy savings and sustainability. Thermal insulation efficiency is a main concept used throughout, and since it measures utilization it is a partial measure of sustainability. It is therefore proposed as a necessary design parameter in addition to a performance indicator when designing building envelopes. The thermal insulation efficiency ranges from below 50% for a wood stud wall poorly designed with incorporated VIP, while an optimized design with VIP placed in an uninterrupted external layer shows an efficiency of 99%, almost perfect. Thermal insulation efficiency reflects the measured wall performance full scale test, thus indicating efficiency under varied environmental loads: heat, moisture and pressure.

The building design must be as a system, integrating all the subsystems together to function in concert. New design methodologies must be created along with new, more reliable and comprehensive measuring, testing and integrating procedures. New super insulators are capable of reducing energy usage below zero energy in buildings. It would be a shame to waste them by not taking care of the rest of the system. This thesis details the steps that went into this study and shows how this can be done.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xiv, 126 p.
Series
Meddelande. Institutionen för byggvetenskap, ISSN 1651-5536
Keyword
Vacuum insulation panels, VIP, serpentine edge, thermal bridge, composite film, gas diffusion, defect dominated, holistic approach, building enclosure, integrated testing and modeling, energy equivalent, field performance, air flow, thermal insulation efficiency
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-90745 (URN)978-91-7501-261-2 (ISBN)
Public defence
2012-03-16, F3, Lindstedtsvägen 26, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20120228Available from: 2012-02-28 Created: 2012-02-28 Last updated: 2012-02-28Bibliographically approved

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