Still worth it. Check your Utility Company--There are all kinds of rebates
and incentives that pay off very well (up to $400) especially if you get the
92% with variable speed blower. Also, where do you think the air (large
volume) for combustion comes from with the 80% furnace? It's air from within
your house--all having been previously heated ($$$) and then thrown up
chimney--it, air, then it has to be replaced with (cold) outside air which
is what gives you the drafts and air leaks and also because it has to be
heated, increases your costs. I think that your house stays more evenly
heated by using the outside air for combustion.
MLD


Can the ouside vent coming into the house be blocked by snow?

Also, I don't understand why using previously heated air for
combustion is worse than using cold air from outside? Any faqs on
this?