Conventional glass materials are weak spots in building fires, and fire codes requires installing fire-resistant glass in specified places. Apart from assessing fire resistance of glass panels by standard tests, there are no universal standards in fire-resistant glass specifications. In standard fire resistance tests, the most relevant performance criteria of fire-resistant glass are integrity, insulation, and radiation. The chemical compositions of the glass products, which depend on the manufacturing method and the required fire resistance standards, are not listed in glass specifications. This article provides an attempt to use calculation method for calculation fire resistance of some types of insulated fire-resistant glass, and describe some specific defects of alkali-silicate gel filled glass. It is shown that recently developed ablative fire resistant glass has some advantage.