HVAC experts: I have a fairly efficient gas furnace for my house. But it is somewhat like a fireplace. It draws its combustion air from within the house so when it is running it sucks warm air up the chimney. I am aware that the most efficient systems draw the combustion air from the outside. My first question is do the systems that draw air from the outside compensate for the temperature of that air by changing the air/fuel ratio as do modern fuel injection systems in cars? Can I gain in efficiently with my present system by simply sealing off the unit and drawing the combustion air from the outside? I am really concerned about heating my home next winter. Thanks for your help.
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