A Velux loft conversion is also sometimes referred to as a rooflight loft conversion but the name Velux has become synonymous with this kind of attic conversion. This is because Velux have over 60 years experience in manufacturing roof windows/lights.
The roof line of your property remains unaltered with this type of loft conversion as the Velux windows are installed so they fit flush to the roof line. This ultimately means that the original roof structure is untouched and you generally will not need to apply for planning permission.
Due to the fact that there will be no major alterations made to the roof the cost of a Velux loft conversion is also likely to be kept down which is another reason why they are increasing in popularity.