Generally, in different countries there are rules base on which the outdoor components of a building’s thermal resistance must not be lower than a specified level.
External components of a building comprise walls and ceiling whose two sides are respectively have connection to the

environment of indoor and outdoor. The other walls and ceilings like the ones that separate rooms or floors are not included in these rules or regulations. In order to specify limits for the thermal resistance of outdoor components, buildings are classified into categories. This classification is performed base on the Geographical location, the application, the city in which the building is, and the building infrastructure.

Complying with limits for those building which are being erected in urban areas are mandatory, and municipalities who are also in charge of licensing Certificate of Completion oversee and enforce these limits. Therefore, if you have in mind to erect a building or to pre-buy one, demand from your contractor to comply with these regulations otherwise you might encounter problems about it.

Optional insulation

As it mentioned earlier, regulations just specify limitations, however, a building can be insulated better and more, and then energy consumption will be more economized . In advance, before implementation of insulation, costs including purchase and installation and the amount of savings because of insulation must be calculated and considered so as to select the most conomizing insulation.