Rationel FORMA and FORMAPLUS design is elegant and have a classic look. The wo product series creates a beautiful architectural appearance, whether you're building from new or refurbishing. The design ensures that a maximum amount of daylight is let into the building. The well-insulated construction makes it possible to let in more solar heat during winter, than it lets out. This means a much lower heating bill during the heating season and significant CO2 savings. Moreover, it improves the indoor climate both for comfort health by minimizing drafts and cold spots.