The CORA Economic system is based on the classic basic design for wood-aluminium systems. CORA uses construction with specially engineered Aluminium Sash-coverings which protect the wood under the horizontal sash that gets a lot of wear and tear as the lower part of the sash is especially vulnerable to weather cycles. The cover design is neat and simple. All standard window designs and types of openings can be implemented in various styles and widths.The aluminium cover is the weather-protective element, and also an architectural element which can be colour-designed at will. Wood provides an outstanding insulation, and gives the house a pleasantly comfortable character.