What is more efficient (when heating a home)?

What is more efficient?

#1 A forced air heating system

#2 A boiler system, whereby the water is heated and air is blown over the radiator to heat a home

A friend believes that a boiler is because the water is only heated for a few minutes every hour.

He says that forced air isn’t because when it is heating the gas is always on.

I think that in addition to heating the water it also has to be moved through the radiator, another energy draw?

Anyone have anything I can cite?

I know that I am probably using the wrong terminology. I guess both could be considerd forced air :wink:


I think the model you need to use with respect to the radiator is a gas-fired boiler providing hot water heat. It heats the water and circulates it through a pipe/radiator system. Very efficient, I think. We just got one.

Your friend isn’t really correct. They are both roughly equal because even though water takes much more energy to heat up than air it retains heat for a much greater length of time (actually, water boilers are a little more efficient because of this).

Vice versa for forced air. Air heats up almost instantly but doesn’t retain heat for very long.

In other words, although forced air will heat up a room almost instantly it will cool off quickly too, meaning it will run more often. A hot water filled baseboard radiator will take longer initially but it will remain hot and provide a much more even heating.

A preference for one or the other is also based on other factors.
[ul][li]Forced air heat tends to be a very dry heat, sometimes too dry (for people and things) requiring a humidifier.[/li][li]Forced air means running much much larger air ducts throughout a home instead of just pipes (which every home will need anyway).[/li][li]Forced air however doesn’t require large radiators or baseboards, just vents.[/li][li]Forced air furnaces are usually cheaper than a boiler.[/ul][/li]
The correct terminology is the type of fuel / type of distribution, IOW gas-fired hot air or gas-fired hot water vs. oil-fired hot water etc.

BTW, in the US hot water systems are much more common than hot air.

Forced air heat can be gas-fired, oil-fired, electric, heat-pump, or ground source geothermal.

Water based heat is typically called hydronic if it runs in loop(s) driven by circulating pump(s). These loops can be physically mounted as radiant baseboards, under floor radiant, or cast into floor radiant.

Low pressure steam or gravity steam is another world unto itself.

Electric heat can be radiant baseboard, or radiant floor.

Electric radiant heat is said to be 100% efficient because all input energy is converted to heat without the losses of fans, circulators, air handlers, etc. The problem is that electricity is comparatively expensive.

The situation described in #2 of the OP is odd, and I’ve only seen it used on a multi zone system where architectural constraints precluded ductwork and there was already a hydronic system in place with capacity to handle an additional zone.

“Best” is a complex equation involving installed cost+operating cost+maintenance cost, with a personal taste modifier. If I had my druthers, I’d vote for ground source geothermal heat pump, the most expensive to install, but cheapest to operate.

Forced-air heating is just nasty to live with: dusty, even sooty (check out the vents to the ducts in a forced-air system sometime), drying out your nasal passages and leaving people with a greater succeptibility to getting sick.

Think you may have that backwards. Of the roughly 15 different places I’ve lived in so far, only one had radiators, and they were steam. Every other home had gas furnaces (forced or gravity) or electric baseboards.

Being gas-fired doesn’t proclude it being air or water distributed. Oil or gas can use either equally well.

I live in the northeast and here its the other way, water boilers outnumber forced air systems. I think that in areas that have significant winters radiators and boilers are prefered. Forced air heating is inheirently ‘lighter duty’ and less expensive to buy & install so they’re probably more common in places that have shorter, milder winters.

Also gas furnaces are more common there because gas is already used for hot water and cooking so it doesn’t make sense to use a special fuel (i.e. oil) just for light duty comfort heating.

A floor radiant system is the best in my opinion. It runs at a much lower temperature and provides more even heating. What you heat it with (gas, oil or electric) is up to you.

the only advantage forced air has over hydronic that I can think of is that it can use the same ductwork for central air conditioning

Lots of opinions offered so far, but very few answers.

As far as which is more efficient, it depends on the efficiency rating of the gas burning equipment (and it doesn’t matter if its the furnace or the boiler). A boiler that is 80% efficient and a furnace that is 80% efficient will both extract the same amount of heat from a given amount of gas.

Your friends opinion, which is based on the amount of time the burner runs, doesn’t mean anything. An 80% efficient 100,000 BTUH boiler and a 80% efficient 100,000 BTUH furnace will both burn the same amount of gas to heat similar spaces.

Which one is better for a given situation depends on many things, including personal preference.