There is a quiet revolution in how windows are specified in cold climates: the triple-glazed unit is no longer a special order. The conversation has moved from whether to use it to how to specify it.
Why the cost changed
Two reasons, and neither is about glass. Frame extrusion capacity moved, and the number of fabricators in cold climates that treat the third cavity as standard rose every year. Both of those are capacity effects, which means the price advantage is structural rather than promotional.
The specification problem
Guidance in most markets still references a single U-value, which is a poor proxy for real performance. A triple-glazed unit with a poor-quality warm edge spacer can perform no better than a well-made double. The building physics is not difficult; it is just that nobody has written the rule down consistently.
What fabricators can do
Publish the whole assembly value, not the centre-of-glass number. It is a commercial risk in the short term and the only durable position in the long term.
