What are the Insulation and Soundproofing effects of Double Window Sash?

What are the thermal insulation and soundproofing effects of the double window sash?
In order to improve the heat insulation of the house, it is effective to increase the heat insulation of the windows that occupy a large area of the wall. One way to improve the heat insulation of windows is to install a double window sash. Therefore, we will explain what double window sashes are and what is different from double glazing that is easily confused, and then explain the heat insulation and soundproofing effects of double sashes.

What is Double Window Sash?
Double window sash has two sashes, one is an outer window and the other is an inner window, and is also called a double window. Double window sash is easily confused with double glazing (paired glass), but double glazing is a window in which two glasses are fitted in one sash. 
​There are cases where double window sash is installed from the beginning when newly built, but it is also possible to install an inner window inside the window frame by remodeling to make a double window.
Only the proprietary part can be freely remodeled in a condominium, but since the inner window is installed inside the room, it can be installed without problems. However, when making double window sash by remodeling, if the depth of the window frame is insufficient, it is also necessary to install the extended frame. In addition, double window sash is basically installed on the sliding window, so it cannot be installed on the raising and lowering windows.

The double window sash has a heat insulation effect and is also effective in preventing condensation
Even if the walls are heat-insulated, if the window occupying most of the wall area is a piece of glass, it is still easily affected by the outside temperature. Through the windows, hot summer sunlight and winter chill may be transmitted to the room. The double window sash is characterized by the fact that an air layer is created between the sashes, making it difficult for the outside temperature to be transmitted. If you install a double sash, you can live in a summer and winter more easily than with a single sash. Condensation occurs when warm air in the room comes into contact with the cold window glass, so a double window sash makes it difficult for the window to cool down and also prevents condensation. If you want to improve the heat insulation, you can replace the glass with double glazing in which air is trapped in the hollow layer between the two glasses, but it is better to install an inner window to make a double sash for higher effect. Also, the heat insulation effect of the double window sash changes depending on the glass and sash used. The heat insulation effect is higher when using a double window sash with double glazing than when using single glass. Among them, Low-E double glazing coats the glass on the indoor side with a special metal film to make it easier to capture the sunlight and prevent warm air from escaping. Regarding the sash itself, the resin sash, which does not conduct heat easily, has a higher heat insulating property than that of a general metal material. Please consider airtightness too when selecting.

The double window sash also has a soundproof effect
The air layer created by the double window sash has the function of blocking sound, which is also useful for sound insulation. Noise can be categorized into two types: air-borne sound that is transmitted by the vibration of air and building-borne sound that is transmitted from building walls, floors, and ceilings. Of these, air-borne sound can be mitigated by using a double sash. For example, if you are worried about the sound of cars and trains passing by in a house near a road or railroad, or if you are struggling with the barking of dogs in your neighborhood, you can expect a sound reduction by installing a double sash. Alternatively, the double window sash is effective as a sound leakage countermeasure for stereo sound at home.

Let's consider double window sash with consideration of disadvantages
A double window sash can be expected to have a heat insulating effect and a soundproofing effect, but it also has a disadvantage. The double window sash will open and close two windows when opening the windows. You may find it awkward to open two windows each time when you ventilate or move in and out. Also, installing the sash inside may create a feeling of pressure. Especially when the extended frame is attached by remodeling, it may protrude more than the window frame so far, so you may feel the room is narrow. A sash with a color that naturally blends with the interior of the room tends to give a clean impression, so it's a good idea to select it while giving consideration to its appearance. The double window sash reduces the heat in the summer and the cold in the winter, which makes it easier to spend comfortably and can be expected to have a soundproof effect. If you find it difficult to live due to indoor temperature and sound issues, consider using a double sash while considering the disadvantages.

Summary
・Double window sashes have two sashes installed in one window.
・Because there is an air layer between the sashes, heat and sound are less likely to be transmitted, and there is a heat insulating effect, the prevention of condensation, and a soundproof effect
・The heat insulation of the double window sash changes depending on the material of the sash and the type of glass.
・The double window sash has the disadvantage that it requires opening two windows and may create a feeling of pressure.

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