What is a furnace?
In a few words?
It's a big gassy box.
This big box gobbles up cold air, spits out warm air, and blows it right into your bedroom while you drift off to sleep.
But don't worry.
They're not always gassy.
Sometimes they use electricity and operate like an oversized hair dryer.
And if you live in New England – or in 1906 – yours may use oil to warm up air before pumping heat through your ductwork.
Where does it live?
Check your basement, attic, crawlspace, or closet.
Is your furnace lonely?
Some furnaces want a friend.
Many homes in the United States have a furnace inside to keep things warm, and an air conditioning unit outside to keep things cool.
But, other furnaces are antisocial. If you live in a colder climate, you may only have a furnace in your HVAC system.