http://www.wordreference.com/enar/shell

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Note added at 32 mins (2015-03-08 12:29:44 GMT)
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وفقًا للرابط الذي أرفقتموه، يتضح أن الأمر لا يتعلق بالهيكل الخارجي فقط، ولكنه يتعلق بهيكل البناء أو المبنى عمومًا

A building shell, or envelope, includes all components that separate the interior spaces within a structure from the surrounding exterior areas. The shell may be composed of many different features, including walls, windows, doors, roofing, footers, and foundations. While the building shell may be made up of various material, it will typically be made from some form of wood, stone, metal or concrete.

The building envelope helps to protect the interior spaces in the building from exterior elements such as rain, wind, and snow. It also acts as a barrier to keep out noise, insects, and intruders. In addition to its role in protecting the interior of the building, the shell provides structural stability for the remaining building components. It also plays a major role in temperature control, while allowing occupants to regulate air pressure and humidity levels within the building. Finally, the building shell acts as a security feature to protect occupants and assets.