Author Options:

Has anyone ever made a room furnace with a light bulb? I've heard of using light bulbs contained in a metal box. Answered

Any ideas. This principle could work along the same lines as an oil hot water heater pumped through a radiator (you know those 300 lb.+ radiators from older houses), but using the bulb in place of the hot water.. If it was portable, that would be great. I could make a nice cover or wood cabinet around it myself. What would be a good metal to line it with that could magnify the heat of a light bulb. Obviously, this would need to be a safe product. Getting a little warm on the outside is not a problem in our home.

I mostly just need some idea as to what metal to use to magnify the heat of the bulb. Thank you in advance for any help or ideas.


You can't "magnify heat"; all you can do is concentrate it in one place, or distribute it. If you're trying to heat a room, putting the light bulbs in the box doesn't improve things over just turning them on in lamps.

In fact the radiator's purpose is to _distribute_ heat -- to take a heat source that would be dangerously hot if exposed, and spread the energy over a larger surface so it transfers to the air more efficiently.

For reference: a resting adult human radiates on the order of 100W of heat.

As far as re-radiating goes: True to some extent. But of course if you've heated the wall, part of the re-radiated energy goes outside and doesn't heat anything inside the room. Which is part of why a heater which either heats the air (if you want the general surroundings to feel warm) or heats a specific set of objects (eg the human) more directly, is likely to be more effective.

Suggestion: Electrically-heated oil-filled radiator heaters are fairly cheap (I saw them for about $35-$50 early in the heating season, depending on size and wattage), and because they distribute the heat over a large area they tend to be less dangerous than most electric heaters. At that price, it may not be worth building your own. And you wouldn't have to replace bulbs as they burn out.

But if you want to do it for the sake of doing it, go for it.

(I'm still trying to decide how best to heat my basement workshop. Since I expect to be producing sawdust I don't want a heater that could be an ignition hazard... but since I've seen IR heaters used in shops, I may be being excessively paranoid. Of course I _could_ just remove some of the heating system's pipe insulation and use the return pipes as "radiators", but there's not much point in heating the basement unless I'm working down there. And I'm not convinced it's worth having the plumber put in another zone, though that's tempting.)

Thanks for the great info. It got me thinking of some other ideas.

You may consider a Japanese method of heating which only uses a small amount of electric heat located under a LOW table. The table is covered with a large quilt that hangs to the floor. Everyone sits or lays down on the floor, with their lower body under the table where it is warm. Otherwise it would take many hundreds of watts to heat a whole room.

I'm sure this works as there would be a lower "ceiling" to keep the heat from rising. However, we need to do other things besides huddle under the table. I realize now how little heat you would get from a light bulb when you would need to heat a whole room. Thanks for the information.

Get the right bulbs though.
You might want to be using high-wattage halogens. 750 / 1000 watt would give noticeable heat.


It will be no different to having the light on in a room - Does that keep you warm?

Well you see that's because the light fixture usually attached to the ceiling.  I think you'll get better convective heat flow if you put it closer to the floor, e.g. using Kiteman's suggestion of putting it under and upside-down flower pot.

In fact I think it would be a lot like a cheery campfire.  I imagine the whole family could gather round,  and everyone could cook hot dogs on sticks...

Well, OK... hot dogs might be tricky, but I bet you could toast marshmallows.  You could definitely toast marshmallows.  I mean the small ones. 


Yes. But a light bulb is a very inefficient heater. It looses too much heat as light. That's heaters that use resistance to generate heat, put out very little light.

.  But isn't the visible light energy absorbed by the container and re-radiated as IR?
.  Even assuming it isn't, getting 5% of the energy out as visible light from an incandescent lamp is great. Most lamps for home use run 2-1/2% or less. Balance heat.

isn't the visible light energy absorbed by the container and re-radiated as IR?


Years ago, the official UK government advice to old folk trying to decide between "heat" and "eat" during winter cold snaps was to fit a 100W bulb in a holder under an up-turned ceramic plant-pot, and leave that switched on in the middle of the most-used room in the house.

It wouldn't keep the room snug, but it would stave off frostbite, and leave enough over from the pension for food.

Another little known fact regarding austerity and incandescent heatbulbs:  The dead bugs that collect in your fixtures are high in protiens, and make  excellent soup-stock!

You can even use one the heatbulbs as an immersion heater to cook your soup with.  You don't dunk the whole thing in, just the glass part, and um... be careful with the trailing wires.

Eww... all the middle-class reflexes I inherited from my mother just kicked in.


Fact: Energy in = Energy out.

If your light bulb draws 1000 watts, it will put out 1000 watts of energy (light + heat). If you aim that light at black metal, that metal will get hot, exactly the same as if you use a different method to electrically heat the metal.

If you blow air over that metal, you'll heat the air. "infrared heating" internally is identical to simple resistive heating.