Tinted glass

You could try taking half the seedlings to the office and see how they do.

Seedlings tend to need good light - vegetables in general, rather than ornamentals that might want shade - so you might find that they are drawn by the lower light. Putting something behind then (white card or polystyrene) will help reflect some light onto the back of them. (Kitchen foil apparently not an idea reflector as creates hot spots thus matt white card / polystyrene sheet better choice).

Other than that I expect it depends on the coatings - some pretty fancy coatings available, and double - triple glazing will reduce the amount of light - so probably the older the glass the more likely it is to be suitable

Most house plants will survive in reduced light - that is of course part of what makes them suitable as house plants so perhaps not a good benchmark for how seedlings will be.

I'd be interested to hear how they do though - hopefully someone else has tried it and can give you a better answer.