Triple glazing in a roof lantern: when is it worth it?

What triple glazing is

Triple glazing consists of three panes with two cavities, filled with insulating gas and fitted with coatings. It insulates better than HR++ glass and also reduces more sound: around 36 dB against around 32 dB for HR++. The U-value is around 0.5 W/m²K, against about 1.1 for HR++.

In the Dutch market, triple glazing is often called HR+++ glass. The idea is the same: one extra layer to keep heat in. A third pane does make the unit thicker and heavier.

• Three panes, two cavities
• U-value of about 0.5 W/m²K
• Sound reduction around 36 dB
• Heavier and thicker than HR++

What triple glazing saves

In our own article we take a 4 m² roof lantern as the example. There, triple glazing saves 65 to 90 m³ of gas compared with HR++ in an average winter season. At a gas price of roughly €1.20 to €1.40 per m³, that is roughly €80 to €125 a year. The actual saving depends on how you heat, the orientation and the energy price.

What the U-value actually tells you is explained under the U-value of glass explained.

Triple glazing cost and payback time

Triple glazing costs extra on top of HR++. The quote shows both types of glass side by side, so you immediately see the difference for your size. Set that difference against the saving and you will see that triple does not always pay for itself within ten years. Especially facing south, where the winter sun helps, HR++ is often more than enough.

There are situations where triple really adds something. Above a bedroom, you notice the better insulation and the quieter glass. With a north or west orientation, little winter sun comes in and heat loss weighs more heavily. On a roof extension with bedrooms, people often choose triple too. More on the price structure under the price breakdown of a roof lantern.

• Above a bedroom
• With a north or west orientation
• When quiet during rain matters

Triple or HR++: how to choose

If you are unsure, first read triple glazing or HR++ glass and HR++ glass in a roof lantern. Better insulating glass keeps the inner pane warmer, which limits condensation on the inside. Bear in mind that complex glass choices can extend the lead time to a maximum of 8 weeks.

Frequently asked questions