The light transmission coefficient 'TL' indicates the percentage of sunlight passing through the glass. The higher the number, the more daylight passes through the glass.
It is usually 68 to 74% for standard insulating glass. Triple and thick glasses are slightly less bright than double glasses.
A sunscreen or tinted glass will automatically be less transparent and will have its light transmission rate reduced to 30% or even 20%.
The lower the energy coefficient 'g', the lower the light transmission decreases. A Selekt glass is a good compromise for a sun protection glass with a TL value of 72% and a g= 42%.