Let the Light In Bi-fold doors are superb at letting light into your home. When closed, they behave as a wall of glass which allows far more light into a room than a standard window or door. Not to mention, upon opening bi-fold doors they completely fold away, removing all barriers from between the sun and your home Aluminium frames are a popular bifold door option as they are slim, durable and low maintenance. Modern aluminium frames are ideal for both residential properties and benefits that can be divided into strength, aesthetics and longevity.