Good, solid, quality workmanship has characterised Rationel’s windows and doors since the first products were shipped from ou ... r factory in Sdr. Felding in 1954. Based on this sound foundation, Rationel is today an international company with sales offices in Great Britain, Ireland and Denmark. Rationel manufactures energy saving windows and doors of premium quality in terms of both comfort and security. Our continuous programme of research and development ensures that the company always meets current statutory requirements as well as market requirements for design and functionality. Rationel is part of DOVISTA Group, which consists of ten leading window manufacturers in Europe with a common mission to bring natural daylight, fresh air and a better environment into people's everyday lives. DOVISTA is owned by VKR Holding whose companies employ approximately 13,500 people in more than 40 countries. read more