Heating a 'Tiny Home' with Infrared Bulbs?

October 26, 2015 9:58 AM

I'm building a Tiny Home on wheels (18' by 8' with a 13 foot high ceiling and bedroom loft) and am thinking about the lowest impact ways to do heat, water heating, etc. I'm considering going all-electric, with no propane or gas, and using solar panels to charge a battery bank. Do any of you know much about Infrared Bulbs as heating devices? I'm looking at the Philips ones.

They are sometimes used for heating workshops or pets in a barn. They are 250W each so I'm thinking that a bank of four or six of them installed on the ceiling in a ~144 square foot house that's well-insulated could do the same job, in a mellow and passive way as a 1500 W Infrared heater of the Quartz style kind.

Those blow air out with a fan, which I would prefer not to have, and then I suspect you may breathe in some small trace amounts of chemicals (?)

Have any of you dealt with heating this way or have any advice? Can infrared bulbs like this work over a range of 10 feet? (i.e. heat something way across the room) Would I need to "cover all angles" with the bulbs to get them to effectively heat the furniture, walls, floor? Thanks!

posted by wavejumper to Home & Garden (16 answers total)

i'm not directly experienced with these bulbs as you're using them but heating a room isn't like lighting a room.

what you're suggesting is more like heating a full-size pool with 6 hoses of hot water at the top of the pool. the bottom of the pool is never going to get particularly warm (heat rises) unless you get the water moving- that's why there's a fan in the infrared heater.

if you were to add a ceiling fan rotating slowly it'd help get the air circulating and improve the situation somewhat.
posted by noloveforned at 10:21 AM on October 26, 2015

Before you get too far, check the math on your power requirements and realistic generation ability. I suspect the power generation from the solar panels during winter will not be enough to operate a kilowatt or more of electric heat reliably and for a useful amount of time (assuming your solar panels are not bigger than your tiny home), even with a large battery bank.
posted by exogenous at 10:22 AM on October 26, 2015 [5 favorites]

Thermal comfort is a combination of ambient air temperature, radiant surface temperature facing the person, air movement and conduction (temperature of surfaces touched). Infrared bulbs boost the second category, although the wattage of the bulb will also increase air temperature in exactly the same way as any space heater.

Your main concern would be Radiant Temperature Asymmetry. As you suspect in your question about range, they also change in effect as a square of the distance. So, what is comfortable at six feet may well be far too hot at three feet.

Is there a reason you aren't just looking at a regular space heater? If electric resistance heat is your best/only option and you have hard floors you could also consider an underfloor radiant system. I'd think the most economical solution in most scenarios would be propane heat.
posted by meinvt at 10:22 AM on October 26, 2015

This is more of an opinion than based on experiential knowledge. It would seem to me that using solar to charge batteries, then run infrared lamps would be really inefficient and wreck your power budget. If you are off-grid, you have to be really miserly with electrical use. Electrical heat is not that.

How about a propane powered catalytic heater? Works great for that size space.
posted by diode at 10:24 AM on October 26, 2015 [2 favorites]

The reason infrared is used in workshops is that it's good for quickly taking the chill off of a space that's normally left unheated. I don't think it has any special advantages for spaces that are generally kept at a comfortable temperature.

Heating with electricity will probably require large batteries and a lot of solar panels to recharge them. You'll want to make sure the structure is extremely well-insulated.

Even if you can theoretically make it work, solar will impose restrictions on where you can park the house in winter.
posted by jon1270 at 10:25 AM on October 26, 2015 [2 favorites]

First of all, those bulbs get HOT. Like, definitely enough to burn yourself. Make sure you install them in such a way that you're not going to touch them accidentally.

And as others above have pointed out, installing these in the ceiling is about the most inefficient approach; the heat will tend to pool in the upper part of the room and it would really help a lot to move the air around with a fan, whether it's installed in the device or just a regular ceiling fan.

Can you explain your particular concern about "chemicals" with that second one? I'm just not sure what you mean based on the Amazon description. An IR heating element plus a fan should not be particularly chemical-y relative to, say, just a light bulb and a fan.
posted by Joey Buttafoucault at 10:26 AM on October 26, 2015

I don't know anything about the building of tiny houses, but for steady electrical heating, could under-floor heating work? They sell rolls of the stuff that's made to go under flooring and heat gently. Since heat rises, this would keep the house more evenly heated than something on the ceiling.

E.g. this stuff: http://www.suntouch.com
posted by permiechickie at 10:45 AM on October 26, 2015 [1 favorite]

This site is handy for doing load calculations. 1000 watts continuous is a big draw from a battery bank. Unless you have a big battery bank but then a big battery bank needs a big solar array to recharge.
posted by LoveHam at 11:26 AM on October 26, 2015

Best answer: I don't have experience with IR bulbs, but if your house is extremely well insulated and sealed (don't forget mechanical ventilation), it won't take much to heat it. Houses built to the Passivhaus standard, for example, are supposed to have a max heating load of 10W/m2 -- a tiny house could get by with a couple of 100W incandescent bulbs.

I use a 1000W ceramic heater in my relatively uninsulated 16' travel trailer, and it heats up the space in a matter of minutes.
posted by bradf at 11:34 AM on October 26, 2015

Response by poster: One reason I'm interested in Infrared heating is that it doesn't heat the air, the problem with a bed-loft is that with traditional heating solutions all the hot air goes up and you have to keep a fan on.
Also just as a reminder I'm trying to be propane-free, for many different reasons.
posted by wavejumper at 11:37 AM on October 26, 2015

Best answer: Yeah, solar for electric heat is going to be rough. The reason we have winter in the first place is because the sunlight is weaker and night is longer. If you're at 40° North, in the winter, if your entire roof were covered in solar panels, you might generate something like 6 KWh a day. Less if there's weather. The batteries and panels would cost north of $5000, and would weigh around 1250 pounds. And that could run 6 of those bulbs at full for just 4 hours a day.

You are not going to come close to the thermal efficiency of a large building that doesn't need to limit the thickness or weight of its walls and has one end stuck in the ground.
posted by aubilenon at 11:44 AM on October 26, 2015

Response by poster: Oh, and I live in sunny California so the requirements aren't -that- tough
posted by wavejumper at 11:52 AM on October 26, 2015

There are some hazards with infrared bulbs:
"The potential hazards of infrared heat bulbs, lamps, and radiators are mainly to your skin and eyes. Because of the intense radiant heat emitted, prolonged exposure can result in severe burns to the skin. Your eyes are very susceptible to high-intensity short-wave infrared radiation as well. Long-term exposure to infrared radiation can permanently damage the eyes. Goggles with special infrared absorbing glass should be worn by people experiencing long-term exposure to infrared radiation. source.
This has more health concerns.

I always worry that a heat lamp will heat a distant surface and start a fire. These bulbs are the same bulbs restaurants use to keep food warm. Do you want to be looking at that all the time?

You might consider electric baseboard heat. Same heat output with none of the hazards.
posted by H21 at 11:57 AM on October 26, 2015 [2 favorites]

There are no particular chemical concerns with quartz heaters. Why not just get a small one of those (one that runs at a lower setting, 500-1000W would be a good idea as you get more energy out of your batteries if you drain them slowly). They definitely make purely radiant space heaters too so you don't have to get one with a fan. This way, you can move the heater around to keep you warm without having to worry about covering all the angles with permanently installed bulbs. I would also be concerned about bumping into the bulbs or getting too close as you won't have much headroom in a road legal tiny house with loft.

That said, I agree with everyone that says you will have a very hard time heating with solar in a tiny house. You'll want that electricity for electronics, lights, refrigeration, and cooking. You probably won't have enough left for heating in the winter, even in California. There is a reason that people end up using propane.

I would only consider this if you had a backup heating plan or you feel comfortable going without heat on dark winter days. It would also be great if you are plugged in.
posted by ssg at 3:05 PM on October 26, 2015 [1 favorite]

A heat pump, aka split system, aka reverse cycle air conditioner will use far far less power than the lamps.
posted by smoke at 6:51 PM on October 26, 2015 [1 favorite]

I'm a big fan of modern forced hot water systems. Not only are they efficient, but they produce a wonderful heat. Not at all like being warmed like a french fry.
posted by irisclara at 10:12 PM on October 26, 2015