Answer: Last question first: You better believe it.
I don't care how top-of-the-line an HVAC system is, if the installer is a dud and doesn't stand by his work, you will most likely be throwing lots of money down the ductwork.
Which furnace is better? That question should be answered by an entity with a professional research staff - Consumer Reports, for example.
Early on, I had issues with my Lennox HVAC system that were solved by a firm my plumber said he'd heard good things about - not the same people who installed it.
Two of my neighbors have Tranes; another one, York. They, too, say reliable service is as much the key to success as the brand. Do your research.
I would install central air-conditioning, especially if you are putting in ductwork anyway.
Make sure that whatever central-air system is installed will cool the entire house, not just the first two floors. That could require zoned heating and cooling for greater efficiency. You don't want to spend all that money then have window units sticking out of the third floor in summer.
There will be a time, not so far away, when houses without central air-conditioning and high-efficiency heating systems will linger on the market longer than those with them.
I'd advise prospective home buyers to ask for the last year's heating and cooling bills, to see whether they can afford the monthly costs of owning a home.
First question last: Speaking solely from my own experience, the answer is yes. I can only imagine what my winter bill would be without my high-efficiency, high-AFUE gas furnace.
But these are questions you should be posing to contractors you interview.
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