Fabric: Curtains made from heavy fabrics such as velvet, suede, wool and tapestry are excellent insulators. They have a dense structure, reducing the penetration of cold or heat. Curtains with special lining reflect heat inward in winter and repel the sun's rays in summer.
This can reduce heat loss in winter by 10% and repel up to 33% of heat in summer.Color: Dark curtains retain heat better, which is ideal for cold climates. Light-colored curtains reflect sunlight, helping to keep you cool during the hot season.
Full Coverage: For maximum energy efficiency, curtains should completely cover the window from ceiling to floor, creating an insulating barrier and preventing air leakage.