Did vikings have glass windows?

Over the last few decades, a number of fragments of window-pane glass have been discovered at sites across Viking Age Scandinavia. However, it is generally accepted that glass windows were not found in this region until several centuries later, when they started to appear in medieval churches and castles. Any window glass found at Viking Age sites was therefore assumed to be a later intrusion and ignored. That is, until a new study was carried out by a team of researchers who suspected that the quantity of window-glass fragments turning up at Viking Age sites was too large to be coincidence