HR++ glass in a roof lantern: what is it and what does it deliver?

What HR++ glass is

HR stands for high efficiency (hoog rendement in Dutch). HR++ glass consists of two panes of glass with a cavity between them. One of the inner faces has a very thin metal oxide coating that reflects heat radiation back into the room. The cavity is filled with a noble gas, usually argon, which conducts heat less well than air.

The result is glass that insulates far better than ordinary double glazing while staying just as clear. You cannot see the coating, but you do notice it: the inner glass surface feels less cold in winter.

• Two panes with an insulated cavity
• Invisible coating that reflects heat
• Gas filling, usually argon
• Clear glass with good light transmission

HR++ glass in figures

The insulation of glass is expressed as the U-value. The lower it is, the less heat escapes through the glass. Our HR++ glass has a U-value of about 1.1 W/m²K. For comparison: single glazing is around 5.8 and older double glazing around 2.8. What those figures mean in practice is explained under the U-value of glass explained.

HR++ glass also reduces sound by around 32 dB. On a roof, you mainly hear rain and hail. A glass roof lantern with HR++ sounds a lot calmer than a thin plastic sheet.

When HR++ glass is enough

For most living rooms and open-plan kitchens, HR++ is more than enough, especially facing south. There the winter sun helps, and extra insulation takes longer to pay for itself. Above bedrooms or with a north or west orientation, triple glazing can be the better choice.

Our quote shows HR++ and triple side by side. That way you see the price difference and make the trade-off yourself. The article triple glazing or HR++ glass sets out the pros and cons.

Combining with other glass options

HR++ is the basis, and you can add other properties to it. Think of a solar control coating against heat, obscure glass for privacy or acoustic glass. In a roof, safety glass is important, so the glass holds together if it breaks.

Well-insulating glass also helps against condensation on the inside, because the inner pane stays warmer. If that is a problem for you, read condensation on a roof lantern.

Frequently asked questions