Blackout vertical blinds can contribute to thermal insulation in a room as they help prevent heat loss through windows, which is especially beneficial during colder months. The blackout material reduces the amount of heat that escapes by acting as a barrier, which can lead to improved energy efficiency in your home. However, the level of insulation provided can vary depending on the quality and fit of the blinds, so it's important to ensure they are well-suited to your windows for maximum benefit.