Heated Furniture to Save Energy?

A lot of cars have heated seats. When the seat heater is on, most drivers will set the interior temperature 3-7 degrees lower than with the seat heater off. Why not apply the same technology to houses?

Imagine being at home in a 65-degree house. Even in a T-shirt and jeans, it would probably be comfortable to walk around, stir a pot on the stove, carry laundry, scrub and clean, walk on a treadmill while typing on a computer (as I’m doing now!). However, if one were to sit down and read a book, it would begin to seem cold. Why not install heat in all of the seats and beds of the house? And sensors to turn the heat on and off automatically? In a lot of ways, this would be more comfortable than a current house because the air temperature would be set for actively moving around while the seat temperature would be set for sedentary activities.

The cost? Let’s say $50 per seat or single bed. Assume that a typical house has 6 rooms, each of which has an average of 6 seats or beds. Round up to 40 and multiple by $50 and we’ve added $2000 to the capital cost of the house. If an average house costs $2000 per year to heat and lowering the thermostat by 5 degrees cuts the cost by 15 percent, it will take roughly 7 years to pay back our investment (assuming nominal cost of electricity). Maybe not the most dramatic way to cut down on our burning of fossil fuels, but it is one that would increase our comfort level rather than reducing it.

What am I missing?

37 thoughts on “Heated Furniture to Save Energy?

  1. Among the exhibits at Plymouth Plantation is a bed which could be warmed by inserting a kettle of hot coals. I wonder why that went out of fashion, particularly in New England.

  2. Why not just heat individuals? Hand them a wireless electric bathrobe as they walk in the door and they’ll stay as warm as they choose. I believe the Intel scheme has a negotiation step to prevent transmitting when no clients are present.

  3. @Joe: It didn’t go out of fashion. Today it’s called an electric blanket.

    But of course, these both point out a big problem with such devices: their propensity to make your house very warm indeed by setting it on fire.

    Here’s a complementary proposal. Instead of cooling entire houses, each room should have an IR sensor that finds each person in a room and the directs a stream of cool air towards them.

  4. In a completely different direction here: One could make furniture that has feet that thermally communicate with radiant heated floors. Some sort of high thermal conductivity surface (copper?) on the bottom of the legs of a love seat? Then some way to radiate the heat throughout.

  5. Just wear a pullover… never heard about it? It helped millions of people going through the cold winters of the pre-global-warming era.

  6. “What am I missing?” A $50 investment is five or six small fleece blankets. I keep my home at 65 to 67 in the winter and grab one of these if I feel chilly. I am comfortably typing this message with one on my lap right now. Perhaps I am eccentric, but I find 65 degrees (or maybe even a bit less) to be about optimal for sleeping and this sans the extra fleece or an electrified bed.

  7. Hi Phil,

    you´re missing a simple fact, humidity. You need a room temperature above 20° celsius during daytime and above 14°C during nighttimes to keep your walls and furniture from collecting all the humidity the air can no longer keep at temperatures below. The longer temperature stays lower than these figures, the more you need to air your house/apartment, which is contraproductive, as you will need more power to compensate on the loss of temperature from airing.

    Anyway, most people tend to keep temperature at 22-23°C which gives you a little room for optimisation. Buy new Windows with optimal thermal insulation (80% of the houses in the states have old windows with simple glass and close to zero insulation) and keep the temperature at 20-21°. You will get the same comfort producing way less CO2 and consuming way less power than before.

    Try it… 😉

  8. Btw. furniture and walls collecting humidity produces mildew infestation in weeks, as will do non insulated walls and windows or insufficient airing.

  9. Interesting idea.

    “most drivers will set the interior temperature 3-7 degrees lower than with the seat heater off”

    What is the evidence for this statement? We drive with our seat heater on (in broken, frozen Britain) but still set the temperature at 22oC.

  10. Joe: electric blankets and coal-heated blankets have obvious safety issues. ‘Why risk it, when heating is *so* cheap?’ I’ll bet the thinking ran for decades.

  11. Sounds like a good idea. I think your costs are low to add the heaters to existing furniture (in a way that is more sophisticated than draping a heating pad over the chair). Plus all the extra cords would be an issue in many rooms, e.g the dining room. But for the living room where most people spend most of their time it sounds like a great idea.

    Of course you could just put on a sweater (my choice when cold).

  12. The principle is valid, but can’t it be put into effect even more cheaply and using even less energy by putting on a sweater when you sit down to read that book and putting an extra blanket (or whatever) on the bed?

  13. You’re missing the cost of heating of the furniture. Adam Carolla (comedian/radio show host/building contractor) has been talking about this idea for years. He had an expert on the radio show that shot it down because the energy cost of the appliances would exceed the energy cost of the more efficient central heating at the higher setting. You’re basically talking about an electric blanket built into the furniture, which not very efficient.

  14. Not missing a thing, per @Joe hot water bottles have been SOP in the UK forever, and before that hot rocks, potatoes and even sleeping on or near the stove. Heated mattress pads (as well as the more traditional electric blankets) are readily available and allow one to turn the thermostat way down. I have an office that’s intermittently freezing and sit on a $12 heating pad counteracting convective heat loss with conductive heat gain. These ideas and devices are all in common situational use throughout the frozen U.S. — particularly the sensible parts of the country that most people fly over trying to get from one coast to the other.

    All of that said, the reality is that electric heat on a large scale is less cost-efficient than gas, you’ll have electric cords everywhere and the delicacy of most of these items dictates that they’ll be replaced every few years. That, and a heated seat will put you into a state of near-bliss requiring a nap or at least civility towards your fellow man (probably a non-starter in the East).

  15. Actually this is the idea behind radiant floor heating. A warm floor allows the temperature to be set about 5-7 degrees lower.

  16. I think the concept would work. The Japanese have heated toilet sets. This seems extravagant at first until you realize that the Japanese do not heat their bathrooms. Which makes sense. Why heat a room of the house that you spend maybe 20 minutes a day in?

  17. Consumer reports also recently recommended the same thing. They suggested turning your thermostat down at night and using an electric blanket to provide warmth. If I recall correctly they did the math to show that it pays off in the long run.

  18. Power cords running to all your chairs could be considered ugly, at least until houses are built with a grid of power outlets in the floor. The plugs would also probably require something like an arc-fault interrupter, so that there is less risk of fire when the heating elements wear out due to overweight people sitting on them.

  19. The principle is sound.

    Since bare feet on a cold floor are, I am guessing, the largest perceived source of feeling that a room is cold, one could start using slippers.

    Next, instead of walking around in a t-shirt, one could wear a sweater.

    Coals in the bed? There are electric blankets.

    Heated sofa? Why not try a Snuggie (TM) instead? The ROI is probably much higher.

    Here at my local university, since we are facing a budget crisis, there are talks of wearing snuggies (http://en.wikipedia.org/wiki/Academic_dress) not just at graduation time, but all winter long to save on heating expenses…

  20. Radiant heat warms the floors. Wood and fabric are poor conductors of heat, but furniture in a radiant heated room is often warmer than convection/air heated.

  21. I would pay the money just for the improved comfort, but can we really expect 40 heated seats to function continuously for over 7 years? The heater in my car seat failed on year three.

  22. We have hot water bottles for beds in Japan. They are recently very popular. They’re called yutanpo. Since Japan houses have on-demand water heaters at the sink, rather than hot water faucets, you can get virtually boiling water instantly to fill up the bottles. They can burn your feet if you’re not careful!

    They sell, and I have, a heated chair cushion (seat and back), and I have a heated folding panel under my desk surrounding my legs. They sell small heated carpets for the floor and pads for the sofa.

    They’re going out of style, but there are tables that have heaters underneath (kotatsu), sometimes with a quilt to cover your legs. My brother-in-law bolted one of these heating units under their dining room table.

    The most important thing is that rooms are small, ceilings are low, and every room has a split ductless air conditioner/heater. The room you’re in is heated/cooled, and nowhere else. My family in the U.S. has super-high vaulted ceilings, giant rooms, and this invention called the “great room,” unknown at the time I left the U.S., which is a humongous combination of the kitchen, living room, dining room, entrance hall, and whatnot, that must have 1 billion cubic feet of air to heat, most of it above the seven feet level.

  23. Yes, electric blankets are good.

    I believe that the high failure rate of heated automotive seats is due to the fact that they are composed of very thin wires that people sit on. Putting a knee into a car seat is probably the death blow for many heating elements.

  24. Folks: As far as the fire risk goes, arc fault breakers are already required by code on all residential circuits in some states and on bedroom circuits in all states. There are electric mattress pads upon which people put knees, etc., and I haven’t heard of those failing. If you go into an older person’s house you will often find working electric blankets from the 1960s and 1970s.

    Sweater/blanket advocates: In a culture where people are too lazy to get off the sofa to tune a different TV channel, I don’t think the idea of constant clothing changes is going to work. Also, Americans have already implicitly rejected the sweater idea. We all have sweaters and yet nearly all of us heat our houses to 68-72.

  25. I was just in Ireland for 6 weeks. It seems that many households rely on heated mattress pads at night, as the cost of fuel with which to heat one’s house there is so extremely expensive. This was a revelation to me! You turn it on a few minutes before you’re ready for bed and then, Voila, a cozy respite awaits! I have started using one at my house in the States and turning the heat quite low at night. Interested to see what I save, if anything.

  26. Microwaves transmitted at the right power level and frequency will agitate water molecules. That’s how microwave ovens work. But couldn’t we have a (very) low power microwave transmitter in each room that (very) gently agitates the water molecules in our bodies and warms us up a bit ? It ought to be very efficient since we’re targeting the energy directly at the thing that needs warming up, and we can generate these microwaves with relatively little energy.

  27. We do the lower heat at night with heated mattress pad approach. Works fine but if the heater isn’t running, then the whole house humidifier isn’t running either, so I end up with unhappy sinuses from breathing dry, cold air all night.

  28. Phil,

    Interesting discussion about space heating.
    However, I am intrigued by your mention of a treadmill workstation. My assistant (avid gym user) really wants one and I am interested in exploring more ergonomic solutions to sitting on a chair all day, but we have only seen photos. I must confess to severe scepticism about it being workable long term.
    Would you mind giving us some feedback? (in a separate post, perhaps?)
    Do you think it would be suitable for an 8-hour working day, 5 days a week?
    What model/brand have you got?

  29. John: I probably should do a separate blog posting on this. Ideally featuring a video of an attractive slender person using the treadmill desk (will have to reach beyond the Harvard/MIT community!). My treadmill is home-made, starting with a Costco NordicTrack “commercial” 3 HP treadmill ($800). Cheaper treadmills apparently cannot handle a lot of hours of operation, even at a low speed. The treadmill is up against a wall, so I got a wall-mount monitor arm for a Dell 24″ LCD (cheap; I didn’t want to spring for the 30″ LCD until I was sure that I would like it). This is not quite ideal because the monitor is not centered over the treadmill (arm not long enough). A conventional PC rests on the floor, plugged into the monitor and with its audio output plugged into the treadmill speakers (designed for an MP3 player). The keyboard and mouse are Logitech wireless.

    The keyboard/mouse mount is basically a tray that my friend Richard and I made out of plywood to drape over the treadmill arms. This places the keyboard way too low for comfortable wrists, so I added an additional shelf on an adjustable angle hinge. This angles the keyboard down and now I can type with straight wrists. The main problem is the mouse, which is still too low and in general precision mousing is hard when walking. So it is great for using a keyboard-only program such as Emacs, but most other apps are somewhat awkward.

    I considered pissing away thousands of dollars on the Steelcase treadmill desk but decided against it because it was going to take 12 weeks for delivery and the treadmill could not be tilted up. The key to burning calories while walking very slowly is to do so at a incline. It is much easier to type at 1 mph than 2 mph, for example.

  30. Phil,

    Thank you for that. Interesting that precise mousing is hard. We use a primarily keyboard-based translation program, so the mouse would not be a major issue.
    How long would you use it at a stretch?

  31. Back on the topic of space heating, the kotatsu (Edward #23) reminds me of a traditional item of furniture in Spanish villages: the “mesa camilla” [1], a table with a brazier of hot coals underneath (now replaced by an electric heater [2]), and covered by a tablecloth that reaches the floor. You sit down, pull the tablecloth up to cover your lap, and your legs bask in glorious heat (your back may not be so happy with the arrangement).

    [1] http://www.altur.es/catalogo/haya/mesas/mesaCamilla23.htm
    [2] http://www.il-lumina.com/articulo.asp?idarticulo=397741

  32. John: I could probably do a better job mousing if I had the mouse higher or if I were able to find my desired keyboard (split like a Microsoft Natural Keyboard but with an IBM Thinkpad-style nipple in the middle). How long do I use it? I’m old and feeble, so maybe 2 hours at a stretch. I’m lucky if I can stand up for 2 hours. Actually I’m lucky if I can get out of bed in the morning. But my young fit friend Shimon has been known to use his all day: http://rura.org/blog/2007/11/14/the-treadmill-desk-exercise-for-the-sake-of-hacking/ (he gave me the idea)

  33. Phil,

    For maybe five years I worked out on an elliptical trainer (Precor brand commercial unit). It too has an incline feature. I liked it because I could read while exercising. Gradually over time I noticed my knees making noises while going up and down stairs. I didn’t make the connection until once while exercising I idly did the math and realized I was making about one million strides per year on the Precor. Oddly, the knee pain did not start until after I quit, but they hurt often for a year or so. I’d use the incline sparingly.

    Study your walking gait and you will note that the knee bends very little on level ground. Increasingly the evidence indicates that running is healthier with uncushioned shoes. In barefoot running one plants the foot directly underneath the hips, so the knee does less bending under load. Also the ball of the foot strikes the ground first, with the heel touching it barely if at all. This style of running employs the glutes more, which I think explains why humans have these huge muscles which are otherwise weirdly underutilized.

    For what it’s worth I’ve used kettlebells for a couple of years and am delighted with them. I look better, I’m stronger, and my cardio health seems good based on weekly jogs. The challenge with kettlebells is maintaining an elevated heart rate for at least 20 minutes. Strength training maintains bone mass as you probably know. My doctor told me that from age 20 one loses between 1/10 and 1% of muscle mass annually, depending on how much each muscle works.

    Best luck.

  34. I just have to chime in regarding the treadmill discussion. Unfortunately, walking at an incline is the way to burn calories, but also hurt your knees! I’ve gotten more out of my weights workout as well.

  35. Many years ago, Scientific American published an energy analysis of heating the people in a house with microwaves. The idea was that people, being meat, would absorb the microwave radiation and be warm while the house would be at the temperature outside. The analysis factored in the saving from reduced refigeration, and pointed out that in sub-freezing climates, refrigerators could be dispensed with altogether.

    Problems left to be solved involved the people cooking if they were to close to the microwave generators, however, the energy savings were substantial.

  36. Working together with our supplier, my company (http://www.funkyfurniturehire.co.uk) is in the process of ordering bean bag chairs that have integrated heating (like car seats). We do outdoor parties and events and everyone knows how cold the UK is … so we have a big need for it. It seems that China can do this kind of technology relatively inexpensively now (costs about $30 extra per chair). But in relation to your comment for inside the house, in my opinion, underfloor heating is the most efficient way to heat a house. It is now possible to drill a borehole within your property and to connect to it a heat pump. You can heat your whole home for free then. Total investment paid off within 5 years. That said I think there could be a strong demand for outdoor furniture to have integrated heating.

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