It is a roll-up curtain that is composed of four distinct layers.
1A front panel which acts as the first layer of insulation and seals the perimeter of the window opening when the curtain is closed. 
2) A moisture barrier which prevents indoor humidity from reaching the window and condensing on the cold glass and window frame.
3 & 4) Wooden battens which maintain the fabric stretched out and thereby ensure that the curtain fits tightly against both sides of the window opening. The battens also create air pockets which further reduce heat losses through the curtain.
5) A back panel which acts as the final layer of insulation and helps seal the perimeter of the window opening when the curtain is closed.

  • Still air is one of the best insulators found in nature, and the Kume curtain contains a lot of it. First, between the fibers of the thick polar fleece that is used to make the curtain, and second inside the thin spaces that are created between the front and back panels by the battens.
  • When closed, the Kume curtain fits tightly against the top, bottom and sides of the window opening. By doing so it traps a layer of insulating air between the glass and the curtain, and prevents the cold air that forms against the glass from seeping into the room. 
  • A Kume curtain basically works just like a good down jacket on a cold winter day. The air that is trapped in the thick layer of down creates an effective insulating layer, and the tight fit of the jacket around your waist, neck and wrists keeps your body heat in, rather than letting it leak out into the cold environment.

  • Kume curtains lower heat losses through windows by 50 to 70%, and improve comfort by eliminating cold spots and drafts in rooms. In the first home that was fitted with Kume curtains, heating fuel consumption dropped by 25% with respect to previous years.
  • They are inexpensive. The cost of the materials that are needed to make a Kume curtain typically ranges from US$ 10 to 15 per square meter. 
  • They are easy to make. Putting together a Kume curtain does not require great manual skills or much time. For example, assembling a 100 by 50 cm curtain takes only one to two hours.

The hardest part of making the curtains is cutting the panels straight and to size. If you use polar fleece for the panels, you don´t even need to hem the fabric, and the whole curtain can be assembled without a single stitch.

  • A Kume curtain can be used on any window whose frame is recessed by at least 3 cm with respect to interior surface of a wall. This is because the curtain works best if it is able to tightly seal the complete perimeter (that is, the top, bottom and sides) of the window opening.

A Kume curtain is much less effective when installed on a window that is mounted flush with the interior wall, because the cold air that builds up on the inside surface of the window is able to flow around the sides and bottom of the curtain and seep into the room.

  • When raised, the curtain forms a tight roll whose diameter varies depending on the length of the curtain and the thickness of the material used. For example, a curtain that is 150 cm long and made of two layers of fleece will produce a roll with a diameter of approximately 12 cm. 

The rolled up curtain does not affect the operation of windows that open outward, sash windows or sliding windows, but it will prevent the operation of windows that open inward. If fitted with Kume curtains, these types of windows will have to remain closed until the curtains are taken down in spring.

  • Depending on the type of fabric used, Kume curtains can be translucent to opaque. Therefore, they are mainly designed to shield windows at night, when indoor privacy is desirable, outdoor temperature are lowest, and heat losses are greatest. In certain cases, however, the curtains can also be used during the day: for example, in unoccupied rooms in which daylighting is unnecessary, and in which the windows do not provide any useful solar heat gains.
  • They can be used as the primary curtain on a window, or used in conjunction with a decorative curtain.