Было бы неплохо...
Кстати - что об этом всем враги пишут...
"Polyurethane is also mainly an insulator. It is used where extreme protection from frigid cold is a priority. It offers the lowest "U" value (approximately 0.09) and the highest "R" factor (approximately 11.1) of all the cores. It also has a relatively low service temperature, which may prevent factory painting. This core is usually not found as a fire-rated product.
Steel Stiffened doors are used mainly for exterior doors, where rigidity is important. They are available in varying degrees of strength and quality. While the thickness of the stiffeners can vary, the majority are made of 20 gage steel. Heavier gages sometimes are used, particularly on security doors. Spacing between stiffeners may vary from 4" to 6". They are usually welded to each other at the top and bottom, and to the inside door skins on 4" to 5" centers. The cavities in between the stiffeners are usually filled with fiberglass insulation....
И еще одна фраза из этой статьи:
Test results sometimes bring out surprising facts...."
