What is a Daylight Opening (DLO)?
Definition of Daylight Opening (DLO) in Construction The actual glass size that is visible. Easily remembered, as the area of glass allowing daylight into the structure. NOT the entire size of the glass panel, due to the additional glass required to allow proper positioning and installation within the sash that is not visible and covered by a window stop.
The daylight opening is a dimension that is not normally used or considered due to the confusion of the actual glass dimension verses the daylight opening. The only real use of this dimension is the actual solar or light calculations required to properly design the heating and air conditioning systems of the structure.
The daylight opening is the actual opening that allows the sun’s heat and the cooling effect of glass to influence the interior ambient temperatures. Mechanical, insulation and solar engineers will use this dimension in their calculations for BTU ( British Thermal Unit ) requirements for the structure.