Advance Glazing System- Energy Efficiency approach for Buildings a Review

Snehashis Ghoshal, Subhasis NeogiSchool of Energy StudiesJadavpur Unversity

School of Energy StudiesJadavpur University

IV th International Conference on Advances in Energy Research

Indian Institute of Technology Bombay, Mumbai

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Objective

In building applications Windows and Glazing units are utilised for light transmission.

This leads to the path for heat flow through the glazing system. This path is normally poor in its thermal characteristics.

The paper reviews various type of glazing units and compares thermal characteristics of such systems.

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Introduction

Since last century, glazing systems have been modified from single glazed to double glazed in different forms and recently developed multilayer evacuated glazing.

In single glazed unit, significant heat gain/loss occurs.

Initially, double glazed units had air as a medium in between.

With the gradual development noble gas filled double glazed units were developed.

In recent days new concept of evacuated glazing units are slowly emerging.

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Glazing Techniques

I. The Evacuated Glazing Technique

II. Glazing System with TIM

III. Electrochromic Evacuated Glazing

IV. Multilayer Evacuated Glazing

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History: The concept of evacuated glazing was proposed by Zoller in 1913 with a patent granted in 1924.

Design Parameters:

1. In evacuated glazing, the internal cavity pressure between two glass panes is maintained at very low value (less than 0.1 Pa).

2. To protect the glazing unit from the stress caused due to atmospheric pressure, tiny support pillars (ss) are used.

3. Edge sealing by transition metal or transition alloy metal maintains the internal vacuum level.

4. Radiative heat loss in evacuated glazing units is reduced by applying low emittance coating.

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I. The Evacuated Glazing Technique

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Schematic representation of double pane evacuated glazing (Fang et al., 2009)

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II. Glazing systems with TIM

TIM or transparent insulating material combines the contrasting requirements of high thermal insulation and high visible transmittance.

Aerogel is a promising material among TIMs for use in windows from energy efficiency point of view.

Aerogel can be classified as monolithic and granular. Monolithic aerogel is not popular for mass production.

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III. Electrochromic Evacuated Glazing Electrochromic evacuated glazing is developed by attaching

an electrochromic layer with a vacuum glazing unit. It can be switched between transparent and opaque state.

Electrochromic films have many potential applications in automotive industry or in buildings that provide shading and privacy applications.

Under all aspect, electrochromic layer should face the outdoor environment .

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Schematic representation of electrochromic evacuated glazing (Fang et al., 2010)

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IV. Multilayer Evacuated Glazing

Triple evacuated glazing consists of three glass panes with two evacuated gaps in between.

Main drawback of such systems is increased weight and cost.

The second cavity of the triple evacuated glazing unit is beneficial because the resulting surface-to-surface thermal resistance is twice as that of double pane evacuated glazing.

A tabular representation regarding thermal property of different glazing systems is given in Table 1 .

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Type of glazing system Description U-value (W mˉ²¯K¹)

Single Glazing One glass pane 5.79-6.3

Double Glazing Two glass panes with air filled cavity 2.78-3.24

Double Glazing Two glass panes with argon filled cavity 2.61-2.95

Double Glazing Two glass panes with argon filled cavity and having night insulation

1.5-1.99

Double Glazing Two glass panes with evacuated space in between

0.86

Double Glazing Two glass panes with monolithic aerogel in between

0.63

Double Glazing Two glass panes with granular aerogel in between

1.69

Electrochromic evacuated glazing

Two glass panes forming evacuated glazing with a third pane having electrochrmic layer

Slightly less than 1

Triple Evacuated glazing Three glass panes with two evacuated space in between

0.26

Table 1 Comparison of thermal properties of different types of glazing systems.

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Conclusion

Extensive research work over the last decade led to different glazing fabrication techniques allowing a wider range of performance of glazing systems. This paper reviews different types of glazing systems and their performances. U-value of different glazing units have been compared.

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References

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8) Zoller F. German Patent, 1924:387655

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THANK YOU

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