Exploration of window systems with innovative glass - especially vacuum insulating glass - for building renovation

Status

completed

Summary

Starting point/Motivation

To reach a high level of energy efficiency, heat and sun protection of the transparent parts of building envelopes is necessary. During the past decades, insulation glass technology up to triple glazing was developed and widely applied by the building industry. However, the high insulation levels of such glasses usually come with the price of a large thickness and heavy weight. This results in heavy structural loads for the frame and thus in rather complex and massive constructions. The mentioned issues cause a limited applicability of such glasses for retrofit purposes (architectural articulation and structural / building construction issues).

Other development efforts in the glazing industry included approaches to construct vacuum (insulation) glazing (VG / VIG). Recently, a China-based company released vacuum glazing products. This development seems to offer large, industrially manufactured, thin and light weight, highly insulating vacuum glass. The product has the potential for construction of new window and façade elements (lighter, smaller and thermally insulating).

Contents and Objectives

The purpose of this research project is to explore the potential of application of vacuum glazing. The major objective is to generate a knowledge base for further development of window/glazing systems integrating this technology, especially in the context of existing building envelopes.

One defined objective of the project was to explore and document required knowledge to offer for future building and retrofit efforts a viable alternative / possibility to increase sustainability. Moreover, the Austrian stakeholders should benefit from "Technology leadership" efforts in this emerging technology field.

Methods

The following approaches were conducted within this research project to reach a preliminary knowledge base about implementation of vacuum glazing:

• Exploration of availability and overall performance of high-performance glazing products on the global market.
• Exploration of design alternatives under consideration of aspects of structural optimization and building physics. This is done via experiments and deployment of simulations.
• Inquiries toward application of vacuum glazing on existing building and in the general retrofit efforts. Moreover, conduction of a market potential survey.
• Evaluation of the energy-saving potential of the application of vacuum glazing on both single buildings and city quarters.
• Construction of a mock-up window (for experiment and presentation purposes).
• Performing of basic LCA-assessment of vacuum glazing.

Results

The results of this research, especially the built mock-up and the numeric thermal bridge simulations and related calculations of building energy demand (prior/after scenarios), indicate a high potential of the vacuum glazing. If appropriate building details can be developed within follow-up projects, a broad application of such high-performance-glazing's can be assumed as a possible alternative for the building sector.

Prospects / Suggestions for future research

While the basic applicability of vacuum glazing was explored within this basic research, the following research questions should be targeted in the close future:

• How should building details, both for retrofit of existing windows and for new constructions, be designed, to avoid thermal bridge impact (pane/frame detail) and to utilize the thin construction width of the vacuum glazing?
• A detailed study about the long-term behavior of vacuum-glazing windows should be conducted. Thereby, the surface temperatures, condensate risk and humidity levels of different construction forms should be explored and evaluated via extensive monitoring on different windows.
• Different further aspects of the performance of vacuum glazing and windows with implemented vacuum glazing should be explored: This includes, for instance, acoustical and visual performance of such constructions.

Project management

Vienna University of Technology, Department of Building Physics and Building Ecology

Project partners

Holzforschung Austria, Wien (HFA)

Department of Building Physics and Building Ecology
Vienna University of Technology
Karlsplatz 13
A-1040 Vienna
Tel.: +43 (1) 58801 27003
Fax: +43 (1) 58801 27093