Possible myth about high efficiency boilers =$$$ to sellers?

Unless someone can properly explain why high 93% efficiency boilers need outside air ventilation intake where as CAST IRON boiller (83% efficient) don't need it:
I believe the only reason is to ****LOWER the flue gas temperature***** and generate condensation which defeats the energy savings purpose (meaning drawing hot air out versus drawing -10F cold air in = same efficiency) since flue gas can only condensate below 130 to 120F???
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Oh, they both need the combustion air.
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HeatMan wrote:

Yes, but the cast iron boilers do not all come with outside air intake vents (same size as chimney exhaust vent) where as I believe all high efficiency condensation boilers do, and the only logical reason I see is they need cold winter air to lower the gas flue temperature since the gas flue only condensates below 130deg F (which should defeat any efficiency gain..meaning efficiency same as cast iron in winter)?
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Reach way up your asshole and pull out some more brilliance!
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