Blog 4. Part 2

Improving Doors & Windows Glass Performance with Low-E Coatings

Double glazed units have four faces; counting from the outside in, you have external face one, followed by faces two and three which are both opposite the internal cavity. Face four is internal to the actual room itself.

Low-E coatings are always applied to either face two or three. In the UAE where the aim is to block cool loss, the coating is marginally more effective on face two where it is closer to the interior of the building.

The difference between hard and soft coat Low-E is linked to their respective glass production. Hard coat is manufactured using what is known as a pyrolytic process; tin oxide is applied directly to the molten glass on the float line, fusing with the glass and producing a durable coating.

Soft coat Low-E uses a thin layer of silver, applied using a ‘sputter’ process to a pre-cut section of glass in a vacuum chamber at room temperature. The finish is referred to as ‘soft coat’ as the coating remains fairly delicate (which is why soft coat is always found on face two or three). Soft coat Low-E has a lower emissivity than a hard coat and therefore can achieve lower u-values for superior thermal performance.