5.1.3Energy Loss

5.1.3.2 Methods for improving thermal insulation

5.1.3.2.1 Use of low emissivity coatings

Low emissivity (low-E) coatings have surface emissivities of less than 0.2. The use of such a coating on glass improves the thermal insulation. They are most efficient when used on the cavity surfaces of insulating glass units. Certain types of low-E glasses such as silver based are used in double glazed units only, as the silver oxide coating will get oxidized if used in single glazed.

5.1.3.2.2 Increasing the width of the air space

Enhanced thermal insulation can be achieved by increasing the width of the airspace. However, there is a convection of the gas in the cavity.

PART 6 STRUCTURAL DESIGN — SECTION 8 GLASS AND GLAZING

5.1.3.2.3 Using gases of lower thermal conductivity

Replacing the air in the cavity with, for example, argon/ krypton, can improve the thermal insulation.

5.1.3.2.4 Inhibiting convection within the air space

Filling the cavity with cellular material reduces convection and makes the cavity a more efficient insulator. However, this usually results in loss of vision, since the materials are, at best, translucent.

5.1.3.2.5 Evacuation of the air space

In theory, a vacuum shall eliminate energy transfer by conduction and convection. However, a vacuum puts high demands on the glass from the external air pressure.

NOTE — Evacuation of the air space is currently considered to be technically impractical.

5.1.3.2.6 Evaluation of type of spacer used in double glazed unit

Thermal performance of the glazing system for conduction can be improved by changing the material of the spacer especially when other options have been exhausted.