On days like these, the reassuring ka-thunk of a radiator pipe springing into action can be music to your ears.

Or is it the whir of the forced air vent breathing warmth into the bedroom so you don't really ever want to leave?

What does it matter? Heat is heat, right?

Well, not exactly. If that were the case, we'd probably be stoking open fires in the living room.

When it comes to your home, there are, in fact, two very different shades of heat — the kind that emanates from a radiator, and the toasty air that's pushed through a series of ducts in your house.

The question, from an efficiency standpoint, is which is better?

Let's start with radiators because, although they often get a bad rap, they've been warming bodies for more than a century. Sure, they can be unsightly, steam-punkish jalopies creaking and moaning every time they get called upon to keep us warm. But those old bones have earned the right to be a little crotchety.

A radiator from the Idaho State Penitentiary Radiators were all the rage in the homes of wealthy Victorians, or even, as in this case, at the Idaho State Penitentiary. (Photo: stellamc/Shutterstock)

After all, that heap of sculpted steel (or iron or brass) in the corner has been around since 1855, when a German entrepreneur named Franz San Galli caught a chill in, of all places, St. Petersburg.

Although radiators have come in many shapes and materials since then, Galli's concept, which he dubbed the "hot box," remains much the same: water, or steam, flows through pipes from a water heater, pooling into fancy metal vessels, which are actually necessarily frilly to ensure as much surface area as possible feels the heat.

And from those surfaces, heat radiates (get it?) outward, much to the gratitude of those who happen to be standing nearby.

But therein lies the rub. Proximity plays a key role whether you're basking in heat or left standing in the cold. People who have radiators in the bedroom, but not the bathroom, can attest to the roller coaster of sensations one goes through when tip-toeing to the toilet in the middle of the night.

Warm-cold-warm-COLD-COLD-COLD!

And then there's the business of keeping these grand dames happy over the years. A well-maintained radiator can be a model of efficiency. In fact the radiators themselves have been known to keep trucking long even after the rest of the house is coming down around them. (You can find mountains of them in salvage yards.)

You'll need to "bleed" them every year — a simple process of releasing excess air from each individual unit — but otherwise, aside from checking for rare leaks, they rarely need replacing.

"Almost always, the radiators are fine," heating expert Dan Holohan tells HGTV. "The boilers usually need to be replaced, because they're either leaking or just completely inefficient by today's standards."

Indeed, that lumbering basement boiler — the bubbling heart of radiant heating — can be temperamental. Often, they're antiquated, filled with nefarious gases from a bygone era that make replacing them a delicate operation. What's more, the supply and return pipes leading throughout the house can corrode over the years and choke off the warm lifeblood flowing through them.

But with millions of radiators in U.S. homes today, these setups still maintain a certain charm. Indeed, there's even a National Radiator Day, complete with the hashtag #LoveYourRadiator.

And they don't have to be eyesores. There are, in fact, some stunning vintage radiators that are as much conversation pieces as they are toe-warmers. Wealthy Victorians, in particular, made radiators into works of art — and warmth.

Then again, some people think heat is best felt. Not seen. Which brings us to the much more modern system that is forced-air heating.

The idea here is that a central hub — that bellowing basement furnace — roasts the air nice and hot, while an electric fan ushers that vital warmth along well-placed ducts and vents.

A basement furnace The heart of a forced-air heating system is the blustery basement furnace. (Photo: Christian Delbe/Shutterstock)

That arterial network has some clear advantages. For one thing, it reaches every nook and cranny of a house. For another — and this is key — there's no warm-up time. No eternal pause while hot water transfers heat to radiators.

Flick a switch and the warm results are pretty much instant. And the warmth flows evenly throughout the house. With vents pretty much everywhere, your nighttime trip to the bathroom isn't a tush-withering exercise in goose-bumpery.

There's another advantage to forced-air systems that you probably don't want to know about right now. But when winter finally heaves its last sigh and the summer sun gets back to doing what it does best, you may want to actually air condition your house. While radiators are rather single-minded in their quest to fire up your home, forced-air systems easily double as central air conditioning set ups. That's a serious upgrade over stuffing your windows with loud, unwieldy and expensive AC boxes.

That's not to say forced-air systems are the zero-maintenance option. In fact, there are a lot of moving parts that need regular maintenance. That blower that pushes the air outward and upward needs to be cleaned at least once a year. And all those ducts need regular cleaning, too. The furnace itself has a near-magical tendency to collect dust and soot in its combustion chamber.

And, unlike radiant heating — where you can "bleed" the pipes yourself — a professional hand is often required.

But much like radiators, forced-air systems are embedded so deeply in a home's bones — ducts typically run behind walls and under floors and ceilings — they pretty much come with the house.

Unless you're building a new home from scratch, the cost of switching heating systems can be prohibitively expensive.

Close-up of a forced-air vent in a house. Forced-air vents certainly keep a lower profile than radiators. But they still need regular attention. (Photo: tab62/Shutterstock)

While the methods may be very different, you might expect the end product — the actual heat — to be the same. But it turns out warmth comes in very different flavors too.

Many people prefer the ambiance of radiated heat to the blow-dryer effect of forced-air systems. As you might imagine having hot air blowing through your house regularly can make for a downright arid environment. Unless you're adding a humidifier to the home setup, forced air can cause dry skin and chapped lips.

Radiators, on the other hand, use convection to heat the surrounding air. Rather than blowing warmth, it's literally radiated, resulting in a smoother, more subtle warmth.

A cat curled up in front of a radiator Radiant heating may be slow to get started, but it provides the kind of warmth that many prefer cozying up to. (Photo: Koldunov Alexey/Shutterstock)

But what cost coziness?

That's the biggest question facing most homeowners. Winters can be long, cruel, and expensive.

So which system is cheaper to run over the long term? Both a boiler and a furnace will use electricity or gas or both to get the job done.

But because boilers have such a long, storied history, they're usually the systems that haven't benefited as much from modern efficiencies. Naturally, boilers installed decades ago, won't be nearly as efficient as a modern hot-air blowing furnace.

Radiators do, however, benefit from an ingenuous and durable concept — one that was blessed with a simple, efficient design from the start.

In the end, the costs of running either setup likely hinge on how well-maintained they are — with radiators, due to their age, being the most likely to lag behind.

But as Terry Harris notes in DenGarden.com, "assuming that both systems are being used efficiently — it is fair to say that there is very little difference in cost."

The U.S. Department of Energy even gives an edge to radiant heating, especially when it comes to floors — for those lucky enough to have them — noting it's "usually more efficient than forced-air heating because it eliminates duct losses."

The real difference in cost isn't so much in running either system, but rather switching from one to the other, which can cost anywhere from $6,000 to $15,000.

So if you happen to already own a house with radiant heating, you might want to think twice about how green the grass really grows on the forced-air heated side.

And maybe be kind to that grand old dame that's been warming bodies since long before you were born — with nary complaint, aside from the occasional groan.

Could this ancient relic still be the best way to heat your home?
Is there a winner in the eternal debate between radiant heat and forced air?