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Integrated methodology for evaluation of energy performance of the building enclosures: part 3 — uncertainty in thermal measurements
Syracuse University. (Building Energy and Environmental Systems Laboratory)
Syracuse University. (Building Energy and Environmental Systems Laboratory)
2011 (English)In: Journal of Building Physics, ISSN 1744-2591, E-ISSN 1744-2583, Vol. 35, no 1, 83-96 p.Article in journal (Refereed) Published
Abstract [en]

Thermal performance of building enclosure is typically based on laboratory tests performed on dry materials without consideration of air and moisture movement through the assembly. To address the field performance of the assembly, however, one must combine measurements and hygrothermal modeling. Hygrothermal models are necessary to include effects of climate and in particular the effects of moisture movement on thermal performance. Full-scale testing is necessary to relate findings of the models to actual construction details. The first paper in this series (Bomberg and Thorsell, 2008) introduced a test program that starting with benchmarking of the R-value of the tested wall in standard conditions, examined the effects of air flow on its thermal performance. This test program does not use the average R-values of the wall as it is in the ASTM testing, but measures local thermal resistance in selected places and calculates the average R-values. The second paper in this series (Thorsell and Bomberg, 2008) applied this integrated testing and modeling approach to selected wood framed residential walls, identifying the magnitude of air flow effects on steady-state thermal resistance, as well as demonstrating that the thermal performance of the top of the wall differs from that at the bottom. It also showed a systematic and time dependent shift in thermal performance caused by moisture movement. In this, third paper in the series, we present measurements performed on metal frame walls that introduce additional sources of uncertainty in the experimental results. We end with a discussion on the need of improvements to testing procedures for evaluation of energy performance of building enclosures.

Place, publisher, year, edition, pages
Los Angeles, London, New Delhi and Singapore: Sage Publications, 2011. Vol. 35, no 1, 83-96 p.
Keyword [en]
full-scale testing, air flow, thermal performance, local measurements, metal frame
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-65785DOI: 10.1177/1744259111404381ISI: 000292288100004OAI: oai:DiVA.org:kth-65785DiVA: diva2:483709
Note
QC 20120126Available from: 2012-01-25 Created: 2012-01-25 Last updated: 2017-12-08Bibliographically approved
In thesis
1. 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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