Answer: Interesting question! According to a botany textbook I consulted,
"Except for the direct effects of heat, the infrared and ultraviolet rays of the sun that reach the earth's surface have little or no apparent influence on plant growth. Plants grow just as well under glass (which filters out most of the ultraviolet) as in the open, if other conditions are suitable."
Light intensity is, I think, the most important factor to consider here. It's possible that new, triple glazed window will actually transmit more light than old double pane windows, especially if the old ones have any dust or condensation between the panes. In any case, I wouldn't be concerned about your houseplants. They'll appreciate the less drafty conditions!
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