BCAB #1450 - Unprotected Openings Below Ground Level, Article 18.104.22.168.
November 19, 1997
Re: Unprotected Openings Below Ground Level, Article 22.214.171.124.
The project in question is a series of unsprinklered townhouses up to three storeys in height and up to 305 square metres in area. One foot eight inch high by five foot long below ground windows are provided with window wells measuring two feet wide, five feet long and 2 foot deep. These windows will be completely below ground level.
Reason for Appeal
Article 126.96.36.199. limits the maximum percentage of unprotected openings in an exposing building face. The exposing building face is defined as the "... exterior wall between ground level and the ceiling of its top storey ..."
The appellant contends that below ground windows are not considered to be in the exposing building face because it is defined as being above ground level. The spatial separation requirements of the code only consider the heat radiating horizontally from the building face. Radiation from the below grade windows would be absorbed by the concrete window well.
Building Official's Position
The building official maintains that the grade should be considered to be at the foundation of the building and not a specific distance away. Several examples are provided of below grade openings that are considered to present a heat radiation hazard to adjacent structures.
Appeal Board Decision #1450
In the absence of a concise definition of "ground level" it is the determination of the Board that for the purpose of determining the area of the exposing building face, the ground level should be taken at the building face. This would include the area of the wall facing into the window well. However, if analysis of the radiation from such unprotected openings shows that a window well or other feature sufficiently diminishes the effects of the radiation, some discretion can be applied as suggested in A-3 of Appendix A.
George R. Humphrey, Chair