Modern A rated windows are generally very well sealed. However one of the most common leakage points in a dwelling is where the window frame meets the external wall/floor. Windows are one of the most expensive elements in a new home & there is little point in spending so much money if they are installed poorly.
Window taping in timber frame structures
The airtight membrane on the external walls in wrapped around the reveal. The membrane is then taped directly to the window frame.