Low E Glass Upgrade in Wellington

The best time to buy it is when you are replacing a unit for another reason. If a fogged unit is being swapped, or a house is being retrofitted, the frame work and labour are already paid for and the coating adds a modest amount per square metre. Buying it later as a separate job means paying for all of that twice.

What Low E does in a Wellington winter

Most of the heat leaving a window at night leaves as radiation through the glass. A Low E coating reflects a large share of that back into the room. Independent guides put the reduction in heat loss from adding Low E at around 30 percent for a modest cost per square metre.

Combined with argon fill, which replaces the air in the cavity with a heavier gas that conducts less, the unit performs better again.

Where the coating goes and why it matters

The coating sits on one of the two internal faces, protected inside the sealed cavity. In a heating dominated climate like Wellington it goes on the room side pane so it reflects internal heat back in. Get that wrong and you have paid for a coating working against you.

It is one of the reasons units should be specified by someone who knows the orientation and use of the room rather than ordered as a line item.

Combining it with other glass upgrades

Low E can be combined with laminated glass for noise, with toughened glass for safety positions, and with obscure patterns for bathrooms. On a north facing room that overheats in summer there are solar control variants that cut heat gain as well.

Specifying Low E correctly

Which face the coating goes on

A sealed unit has four glass faces. The Low E coating sits on one of the two inside the cavity where it is protected. In a heating dominated climate it goes on the room side pane so it reflects internal heat back in.

Put it on the outer pane instead and you have paid for a coating that works against you for most of the year. It is one of the reasons units should be specified by somebody who knows the room, not ordered as a line item.

Solar control is a different product

Standard Low E is designed to keep heat in. Solar control Low E is designed to keep heat out, and the two are not interchangeable.

On a north facing room that overheats in summer the solar control variant is the one to ask for. In every other room in Wellington, the standard one.

Low E Glass Upgrade at a glance

What it is

Thin metallic coating on an internal face of the sealed unit

Effect

Around 30 percent less heat loss for a modest cost per square metre

Argon

Cavity gas fill, improves performance further

Position

Room side pane in a heating dominated climate like Wellington

Combines with

Laminated acoustic, toughened safety, obscure patterns

Best time to buy

When a unit is being replaced for another reason