Why are my feet cold?

I have an annual (bi-annual) ritual. The Changing Of The Bulbs. Near the equinoxes I swap light bulb type in some lights. It is also a good time to shake the stray bug body out of the glass globes and to wipe / wash off any accumulate dust and grime that would dim the light. A significant amount of light can be lost to a dirty fixture or bulb.

It is also a time when I look for “marginal bulbs” in hard to reach places. So a CFL with dark ends to the glass gets placed in easy to reach fixtures as it is “on the way out”. Sometimes I also “play with the lighting” in the process. Using that 4 to 5 minute CFL warm up to full brightness to effect in some places (where I do NOT want a blinding flash of light at switch on) and using incandescent instant-on in others (like security lights and the fridge). The Green Fascists have tried to prevent such fine tuning of energy vs benefit via a ban on incandescent bulbs. That resulted in my having a ‘lifetime supply’ of cheap incandescent bulbs in a corner of my office… One does not wish to have a mercury source in the fridge where a stray ketchup bottle can set free the mercury, and you buy a new fridge… One does wish security lights to be ‘instant on’ and not “Please wait, dear crook, for just 3 or 4 minutes more while my dim bulb warms up”.

All my incandescents are on dimmers. Both for the wonderfully liquid soft lighting options, and as that extends the bulb life greatly. Depending on degree of dimming, it can be decades. (If run about 1/2 brightness and fairly yellow, but also inefficient.)

For me, the Kitchen has always been… problematic. Some many years (decade+?) years back the Green Fascists got a building code into California (and likely more) places to demand fluorescent lighting in the kitchen. In the process mandating that “green eggs and ham” be the reality for all rather than just a kids book; as the CRI Color Rendering Index of the typical tube fluorescent fixture used is, um, ‘not good’… Lucky for me, I have an old house with an old glass bowl and bulb in the ceiling.

Over the years, that fixture has had many kinds of bulb in it. I tried a ‘circle line conversion’ adapter. A screw in thing that has a round / flat fat cylindrical shade on it. It was OK, but a bit on the dim side and while sometimes the “slow start” was a feature (in the early mornings for me, getting ready for work), often it was not. Typically it got a 100 W IC bulb most of the time. As the years have passed, that’s moved up to a 150 W bulb. The added brightness tightens the pupil and the eyes focus better with the pin-hole camera ;-)

Trying CFLs has been a bit dismal and all the LEDs shout at you not to put them in an enclosed fixture. As I like my spherical glass bowl, they are a non-starter. Especially after 10 minutes of use in it… CFLs have been a similar challenge. They, too, are placarded “not for enclosed fixtures” (which is all of my built in ones…) Anything small enough to cool is too dim, especially in the first 5 minutes. Anything bright enough has a very short life. After several years of looking, I’ve finally found a CFL that is bright enough, yet does not overheat. I also put on a newer, larger, glass bowl so there is more surface area to radiate. Not enough more for prior bulbs, but this one is doing OK (so far).

The Sylvania I tried died inside hours. This one has been going for about 1/2 year now, and doesn’t show overheat signs (dark plastic, hot to the touch, smell when running for a while, etc.) I’m generally pleased with it. It is a 2050 lumen class bulb, so even has enough to be ‘bright enough’ on early morning or late night runs to the kitchen during the first minutes of dim… Earthmate “superbright” 30 Watt bulb from Lowe’s. Says it replaces a 125 W bulb, but I think a 150 is more like it. Good CRI too. It is now the “standard kitchen bulb”.

OK, now it’s winter. I’m pondering bulbs. In winter, the “waste heat” of an IC bulb just warms the house up. Being in California, this isn’t a big deal. Heck, we usually have a couple of windows open an inch or two all the time unless it is darned hot or darned cold outside, just for the gentle ‘turn over’ of the household air. Still, it is noticeable. Our heater is a gas fired unit with a blower that circulates to the whole house. It isn’t as quiet as I’d like. But it works. Flame bar about 2 feet wide and 2.5 fee long. LOTS of fire. LOTS of CO2. LOTS of heat. So when it comes on, we get noise, and a flush of heat, then it circulates just a bit and shuts off. This tends to mix the floor layer of cold air in with the heat, but not as much as I’d like. There is a significant stratification from floor to ceiling.

So my feet are cold.

Having fewer “whooshes” and some hot spots at table lamp level makes it a bit quieter and better mixed.

In winter, as most times, I only put on shoes and socks when I go outside (and not always then, even in winter). It’s not like I can’t put up with cold feet. I’ve gone barefoot in the snow and not had much of an issue with it. Heck, my Celtic ancestors ran around Europe buck naked. Clothes are an interesting invention, but clothes and shoes are much over rated.

Still, my feet are cold.

So last night I decided (after much pondering while doing dishes and other mindless tasks) that I would go ahead and have the “Changing Of The Bulbs”. That I had enough ICs in storage that I could afford that luxury. That while I had matched many bulbs to their places well enough that they need not participate in The Ceremony, there were still one or two.

The general “bulb plan” is to have a background CFL or LED bulb in every room. That way “standby” and “background” light levels are the most efficient and least costly. A lamp at the end of the hallway, for example, has a CFL bulb (finally found one!) with the ‘regular bulb shape’. The shade “clips onto” the bulb, so it was get a bulb shape or no lamp… That one does not change. It gets turned on, and left on, for most of the day. Warm up lag is not relevant.

The “entry light” to the bedroom is on a dimmer. This is so that I can sneak in at night without waking the spouse (who sleeps early) and she can sneak out without waking me (who sleeps late) and we both can come and go in the middle of the night with only dim lighting. (First put in when infant children required frequent mid-night tending, now used for, um, other potty breaks…) Yet it can be turned on “full bright” for times like cleaning the room, or trying to find that dark sock on a dark carpet under the dark bed. Or just for reading “mice type” sized print. That bulb is a “dimmable Halogen” at the moment. Sometimes it has been a regular IC bulb. I’ve tried various “dimmable” CFLs. Not one of them is adequate. The LED, we saw, worked, as long as we didn’t mind being awake all the time…


So the LED bulb has gone where all things disappointing go. The Garage. I have 5 light fixtures (not counting the 2 workbench lights of long tube fluorescents over the two workbenches I’ve not seen in coons-years due to the “stuff” now “stored” there. One is my loading bench. Still working off inventory “put up” 15 years back. Though reaching an end. I don’t shoot much now, it seems.) So the others get the Unsatisfying Bulbs. Also the “Yard Light String”. I have 5 more screw in fixtures around the back of the house over the yard. So 10 total “whatever” places to put disappointments. Things that make Franken-Eggs Slime Green and Orange Ham. Things that flicker on startup (not seen since my early days with CFLs. I was using them before they were trendy. Back when you had to build your own with PL screw in converters and magnetic ballasts. I’m NOT anti-CFL, I am pro-choice and pro-optimizing.) Between those 10 fixtures and my “propensity to investigate”, I’ve not bought a bulb FOR the garage or yard in decades. The rejects just go there to live out their lives in solitude…

In the house, there are, now, 3 bulbs on dimmers that are IC bulbs and one that is an LED (most of the time). Bed, Bath, Entry hall, and Office. I figure that in the office I can use all the “Stay Awake!” blue 540 nm light I can get! ;-) The bath is a similar small glass bowl that cooks CFLs, though that didn’t stop me trying. As it needs less total brightness, I could just barely get some that didn’t cook and were bright enough. The spouse and daughter were never satisfied with the CRI as they do make-up. I was never satisfied with the “5 minutes of dim then too bright”. Not dim enough for dead of night “visits”, and too bright by far if the “visit” was not over quick. Not bright enough for “emergency surgery” (on injured pets, or sometimes on me to remove various plant parts from plants wishing to express their displeasure at my “help”… cactus in particular is very unappreciative.) And no CFL on a dimmer works worth a damn.

First, it requires a ‘special’ dimmer. There goes $20. (I have 3 now…) Second, they never go Really Really dim. If you do that, the CFL overheats and burns up. (I have 2 or 3 of them, now, in my “toxic waste disposal needed” bin). There is NO guideline for where the right minimum set point is located. You learn it by trial and error and error and error and Damn-it-just-put-it-bright. Then, when you turn it on dim, it slowly brightens over then next 5 to 10 minutes. (Ever try to leave the ‘pot’ to adjust the light while not leaving the ‘pot’?…) Then, when they are stable and not-quite-dim-enough, they hum. When sitting quietly in the dusky light contemplating things, having a bumble bee humming next to you is, er, distracting.

So the “dimmable CFL” is a “polite lie”. Something that can be done, but only inside so many caveats as to be useless. Thus my stash of IC and Halogen bulbs.

I’d thought LED bulbs would get me past that, but they don’t. Far less hum. Full dimming range. But the color does a reset on your “awake time” clock, so not the thing you want in the dead of night on a potty run… Nor in the evening when sliding off to bed.

That means those bulbs no longer are part of The Bulb Changing Ceremony. In fact, between the places where I have a CFL that works, and where I’ve just decided it MUST be an IC until really non-blue LEDs come out, I’m really down to just 3 or 4 bulbs total. A lamp in the living room was one of the last ones. I’ve put ICs on a dimmer in it, though, so not this year. The kitchen was now a pretty darned good CFL, so I was pondering not doing it. Maybe just leaving things “as they are” this year.

But I had bought an inventory of the very nice high power Halogen bulb that I’d thought was the only thing that would work in the kitchen (prior to finding that CFL), and I’m not sure what lifespan I’ll get from the CFL… So the optimal decision is to swap. Extend the life of the CFL, do a “use over my lifetime” of the 150 W halogen in the funny narrow bulb shape. (BT like a cylinder with a bulge in the middle).

Last night I did the swap.

It’s brighter than the CFL. ALMOST too bright on late night trips to the kitchen. I’d taken out the dimmer when the CFLs were going in, so it no longer has the “soft start” feature. But it is great CRI and lets me see clearly when cooking and cleaning. Important points in a kitchen. I’m still not sure it’s the best choice without the dimmer, but wanted to find out if “Halogen sans dimmer” is better, or not, than the “CFL that’s about right”. Besides, it was Bulb Changing Season and old habits die hard.

This morning was The Test. Would a morning run to make coffee be Just To Damn Bright? Turns out it wasn’t. A tiny bit bright, but OK I guess. ( I’d rather have a 125 watt to 150 W IC bulb at 2000 lumens, but don’t have many and can’t get more. This more efficient halogen bulb is 2450 lumens, so about 400 lumens more than optimal. Good enough, though. )

So there I was in the kitchen, under my 150 W bright and hot Halogen bulb, making coffee in my bare feet. I reached up and could feel the heat from the glass globe. It’s a nice little heater. The warm air spreading out over the kitchen ceiling. No doubt radiating IR into the rest of the room. As I sipped my hot coffee, feeling all warm and comfy from the knees up. I wondered:

Why are my feet cold?

Here I am, inside a box that’s 8 FEET tall. Less than 3 meters. I’ve got a hot IR source over head. Not 20,000+ feet up at the tropopause. Just Right UP THERE! It’s nice and hot, I’ve put my hand up there. I can feel the IR hitting my hand. (One side warmer than the other). There’s plenty of CO2 in the place. It’s winter, so the windows tend to closed. We’ve got 4 people in a small place (about 1000 sq. ft.) making CO2. Sometimes I even use my kerosene lantern or cook over an alcohol stove. CO2 inside is usually far higher than CO2 outside. IFF CO2 is such a great absorber and re-emmitter of IR, so good that even just a 2 W difference between 20,000 feet up and the ground can “warm the ground”, then what about that 150 W difference between just above my head and 8 feet lower?

Why are my feet cold?

The warmer air spreads out over the entire ceiling. There’s an entire layer of warmer CO2 all over the house. When the heater kicks on, it sucks air from the floor level, heats it, and spreads it back through the house. One of the ‘defects’ IMHO is that it does this from ceiling registers. That puts the ‘hot layer’ up near the top. Now it runs long enough to circulate the whole house volume, so it’s OK for a little while. Then things stratify again. There is a cold layer that’s about a foot deep down on my feet. It can be 10 F colder than the middle of the room (depending on heater status. Sometimes we leave it off). Top of the room can be even warmer (by feel – I don’t have a thermometer up there). What is very clear is that there is strong stratification due to convection.

In short, my feet are cold because CO2, even at very enhanced levels, even with 100 W scale differential inputs, is unable to move heat from ceiling to floor. Convection kills it.

If my feet are cold, how can CO2 warm the planet surface via IR?

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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29 Responses to Why are my feet cold?

  1. punmaster says:

    Clear and simple analysis in easily understood terms. Thank you.

  2. crosspatch says:

    Well, CO2 doesn’t “warm” anything. It should work by making things less cool. For example, greenhouse warming would show up as an increase in nighttime lows, not an increase in daytime highs. It increase the average temperature by increasing the lows. In the daytime the CO2 in the atmosphere blocks as much (or maybe more) LWIR from the sun as it does that radiating off the surface of the Earth. At night is where it would be most seen and that is the reason why we would expect to see polar amplification. CO2 should make for less cooling in the winter when there is no sun at the pole. We aren’t seeing it.

    This brings to mind why I believe the famous “salt house” experiment was done wrong to begin with. In that experiment two houses are made. One with a glass roof which blocks IR and one with a rock salt roof that allows IR to pass. Then both are given some equal amount of radiation from outside the roof and the temperatures of each one checked after some interval. I would actually in this case to expect to find the rock salt one a little HOTTER (which is what happened relatively recently when someone attempted to duplicate the experiment) because the rock salt roof would allow more LWIR *in* from the radiation source.

    The way the experiment SHOULD be done, in my opinion, is this way:

    Construct two houses. The roof of ONE house is a double pane of glass. The roof of the second house is a double pane of rock salt. This reduces conductive losses and actually more accurately describes our atmosphere with the stratosphere as the middle gap. Now, making sure that both houses are the same temperature, in a cold, dark room (freezer?), place a hot brick in each house where both bricks are the same temperature and record the cooling of the bricks in each house.

    I would expect the rock salt roofed brick to cool faster as LWIR is free to radiate out of the box while in the box with the glass roof, the glass would absorb the LWIR and radiate a portion if it back into the box.

    “Greenhouse warming” shouldn’t increase daytime highs, it should moderate nighttime lows.

  3. adolfogiurfa says:

    @E.M.: CO2 and cold are always related: Dissolve baking soda (sodium bicarbonate) and ammonium bicarbonate in a glass.

  4. Terry Jackson says:

    The heating and cooling guy put in a new thermostat. It has a couple functions to run the fan continuously or intermittently to equalize the room temps. The fan control is somewhat independent of the actual burner. A simple box fan set at an angle near a corner would likely achieve the same result in a single room. Just a thought.

  5. KI says:

    No instant on CFLs in California? (And I do mean instant on… <10s to full on.)

  6. Bill McIntyre says:

    Heat radiation travels from warm to cold . Your feet are in the vicinity of the upper 90’s F

  7. John F. Hultquist says:

    Our programmable thermostat (for an air-source heat pump) is in the center hall of the house. End corner rooms will cool soonest. I have a small oil-filled electric radiator 14” high. My computer table is a finished laminated door on two low book cases facing in. A nice little heat trap. Works great. I investigated alternatives, such as a pad, like for a cat or dog housed outside. Those things are way too expensive. A cage-enclosed trouble light would probably do the trick. Sorry, I’m not supposed to use that last word in any climate related text.

  8. Petrossa says:

    I have halogens everywhere. Best buy, and they work with standard triacs which prolongs their life enormously.

    But on changing of lightbulbs, i’ve made one room 5 meters high by knocking out the ceiling and put random dispersed lights with the idea it looked like a starry sky.

    Never gave it a thought i had to change them one day. In the end i had to do a dangerous balancing act with a chair on too short ladder.

  9. E.M.Smith says:

    @Terry Jackson:

    Thanks for the idea on the box fan. I’d thought of a pipe and coaxial fan, but as I have a box fan that would likely get done… ;-)

    Presently we have a ‘roll around oil filled electric heater’ in each bedroom. When the house is ‘shut down’ we used them for local heat in any one occupied room. If it bothers me to have cold feet, I’ll turn one of them on and that will heat and lift the cold layer until it is gone. Not as cheap as the gas heater for whole house use, though. Then again, this is California… so it’s not like ‘heating bill’ gets my attention…

    (We just re-lit the heater last month… it will be ‘off for the season’ in March or April. It isn’t run at all at night, and even the room heaters in the bedrooms are a ‘once every couple of weeks’ when a Cold Canadian makes it over the mountains. Mostly it’s just a ‘warm the house up in the morning’ and then a ‘keep it warm from dinner to bed time’. Just 350 miles south there may or may not be a heater in a house at all… One apartment I looked at had a 1 kW resistive thing in one wall about 1 foot on a side. Turned it on to test it. The ‘burned dust’ odor informed me it had not been used ‘in a long while’… as did the person showing me the place…) Or I could just put socks on when I wake up and go to make coffee ;-)


    Sounds like a really good test…


    They may exist. They are not in my inventory. I did buy one for a friend when in Florida. It was 10s to ‘pretty good brightness’ but not really fully bright. When stocking up on IC bulbs I figured that the “subsidy” for CFLs was likely to end once they were mandated, so I also stocked up on subsidy CFL bulbs. I’ve got about 2 or 3 dozen of them. Paid about 50 CENTS each. (Some were special… I paid 70 Cents for them ;-) So I could likely find some “instant on” bulbs for $7 to $10 each now that prices have jumped up. (The not-so-good CFLs are about $4 to $5 each now). But my inventory works for all the places I have CFLs ( i.e. not in dimmers or ‘3 way lamps’)

    Mostly I use CFLs where the “instant on” isn’t needed anyway and the slow-start is a feature at ‘first light and dead of night’. For outdoor security lights you get the added problem of “cold start” where many CFLs just don’t cut it. (As I’ve come to appreciate in those banished to the Garage…) Yes, you can get low temp CFLs too. The problem is the search cost of figuring out which all of these features are actually in any given bulb (and not just quasi-claimed) enough to work where you want them. Then typically I find out the CRI sucks or it hums or… So I have had a long string of bulbs end up in the garage and outside over the years. Did I mention I was “into” CFLs before the CFL existed and you had to “roll your own” out of PL bulbs, screw in adapters, and external magnetic ballasts?…

    So I’m no longer really interested in the search costs of trying to “fix it” by once again doing a ‘bulb survey’ of a dozen bulbs trying to find what really works. I have enough bulbs in the garage ;-)

    My “stash” is fine on all counts (CRI, brightness choices, efficiency, cold-enough start, low to no hum, etc.) for any need I have now other than really, honestly, truly, full range, dimmable. The only place where “instant on” is really “an issue” any more is the kitchen, and that fixture demands a particular peculiar power / efficiency / CRI combo that could only be found after trying damn near every “125 to 150 W equiv.” bulb in the local hardware stores. ( I now have 3 or 4 in my ‘stash’ to someday go to the garage…) So mostly we just leave the kitchen one on a lot. Only time the really slow warm happens is in the early morning. (And that’s not my problem anyway. ;-)

    At one time I had a motion sensor security light over the garage door. THAT would be a problem for CFLs. But some time back I replaced it with a dusk to dawn HPSodium fixture…

    But yeah, if you can find for me a 100 W equivalent, 90+ CRI, instant full brighness, really really dimmable to 10 W equivalent or less, that works in a 6 inch glass bowl, CFL and I don’t have to buy 10 bulbs to figure out which one it is; heck, sure, I’ll replace 2 of my remaining IC bulbs with it… Make it a ‘3 way bulb’ at 50, 100, 150 W equiv and I’ll do another lamp. Make THAT so that the lamp shade can clip onto the A-type bulb shaped envelope, one more…

    @John F. Hultquist:

    Interesting. We both came to the same solution. Oil filled mini-roll around in each bedroom / office. Only use the ‘big house heater’ when folks are using the whole house. Or first thing in the morning to get the whole place ‘warmed up’. Or when a Canadian Express is just soooo cold… but even then we put the perimeter electrics on to kill the cold pool at the floor. The one in ‘my office’ is next to the desk. I have an IC flood pointing down at the work surface from above during winter. “Click Click” the space is comfy and I don’t care about the living room… or the ceiling…

    Then again, any given day can be 80 F … Here’s the “Almanac” entry from Wunderground for today:

    Temperature	Forecast	Average	Historical Range
    High    	59 °F   	58 °F 	48 to 97 °F 
    Low     	37 °F   	41 °F 	28 to 53 °F

    Note that Historical High. 97 F. In January. Average is 58 F. I’ve known folks who thought 60 F was called “summer” ;-) Yes, our winter January is on average about the same as an Alaska summer day…

    So to all of you making “how to stay warm and comfortable suggestions”: I do appreciate them. I really do. But I also feel really guilty because, well, um, it just doesn’t really get cold here… Note the “historical range” cold was just a few degrees below freezing? On an ‘extreme year’, we get a ‘hard frost’… in the dead of night…

    Yeah, tonight is forecast to be ‘very cold’ and a full 4 F below average. It’s a cold cold winter… and we’re still 5 F above freezing… (The heater is off right now and I’ll be under the covers when it’s cold outside). By morning the interior is likely to get down to 50-something F or so. At that point, a couple of quick runs of the furnace and we’re back up to 70 F. Then we just wait for mid-day…

    (Though tomorrow is forecast as “much colder”, so may be bitching again tomorrow ;-)

    Our “furnace” has a 2 wire control, so I can’t run the blower separate from the heat. Then again, we don’t really get cold enough to care much. If I really cared, I’d turn on the oil-filled in the bedroom or bother to put on socks. Then again, that has a catch-22… I’d need to have coffee to be awake enough to remember to do those, and that means making the coffee, that means going to the kitchen barefoot in the morning, that gives me cold feet, that… ;-)

  10. crosspatch says:

    The cold feet you describe is why the Eichler homes in this area were heated from the floor. They were built with a concrete slab that was heated by pipes inside the concrete connected to a boiler. Problem is they were designed to be cheap homes and the floor heating has failed in many of them. There’s a whole neighborhood of those houses near me.

  11. E.M.Smith says:


    Ah, yes, the “cheap tubing the the poured slab” era… When they forgot why houses were lifted off the ground on perimeter foundations and why pipes inside poured concrete might be hard to fix…

    FWIW, I’ve got a ‘craw space’. One of my “someday” projects is to plumb a couple of baseboard hot water radiators into the Living Room and Master BR and hook them to the water heater. Our demand is usually so low that it could keep the place warm (other then when the Cold Canadian hits..) Haven’t done it mostly from sloth and lack of need. Maybe if this is a Grand minimum… ;-)

  12. philjourdan says:

    I have not studied my ancestors, but I never wear shoes – unless going to a store or someone’s house. And that includes the dead of winter, or the peak of summer (except in the Valley when it is 120 out – then I wear Sandals). As I read your article (understanding it was about CO2, not necessarily cold feet), I could not remember a time when my feet are cold. I am sure they have been. I just do not notice it.

  13. DirkH says:

    The mean free path length of an IR photon in the CO2 absorption bands is about 30m given current atmospheric concentration. Even if you have 10 times the concentration in your house it’s still 3 m.

    And worse; the absorption bands of CO2 (4.3 µm and 15 µm) are totally incompatible with human body temperature (or any other object at realistic surface temperature). Humans emit IR mostly at 10 µm; corresponding to 310 K, see Wien’s Displacement Law.

    CO2 absorption bands correspond to roughly 200 K and 600 K respectively.

    So your setting is extremely unsuited to testing the GHE of CO2 (as is Earth).

  14. E.M.Smith says:


    I only notice it because I notice everything… It doesn’t bother me (or I would put socks on). It just is. A part of situational awareness. I do have to admit, though, that riding a steel pedal 10 speed bike in the snow barefoot, I noticed the cold as cold. Walking on the show, I noticed!


    Interesting line of analysis… I think I’ll look into that ‘effective K’ point…

  15. Steve C says:

    I’ll second Terry Jackson’s suggestion about the small fan, having messed around with the idea myself. Ex-PC ones work very nicely, maybe underrun a little to keep them quiet if necessary. If you’re redecorating, the fan can be put on a strip of 3-ply, hardboard or other cheap panelling down one corner of the room and “disappeared”. If not, it still helps if you just make up some sort of bracket to hold a fan in place on high, blowing generally downwards. An unexpected side effect is that it can also make summertime temps seem cooler, just by keeping the air moving. An ordinary 80mm PC fan, at its nominal 12V, can shift about 96 cubic ft per minute, a.k.a. “plenty”.

    Re “undervolting” incandescents, a rule of thumb I came across decades ago is that if you undervolt a bulb by 10%, you get 10x the life; if you overvolt it by 10%, you get 1/10 the life. I have a couple of “incandescent striplights” – the sort with a filament down the middle of the tube, which ordinarily don’t last very long – which have been running under my shelves for many years now, with 20V subtracted from the 240V supply using an old transformer. They give a nice “warm” light, easily enough to see what you’re doing on the shelf below, and on present indications will still be operational when I am not – that’s on a switch, too, not a dimmer.

  16. J Martin says:

    Modern underfloor heating is very good, water in plastic oxygen barrier pipes, via a gas boiler. Not cheap to retrofit sadly, but gives a more even vertical spread of heat. Reputedly cheaper to run and works well from the output of heat pumps, ground source or air.

    I have ordinary wall hung radiators and keep toying with the idea of ripping them out and retro fitting underfloor heating. One day perhaps.

  17. A few months ago we moved into the house I spent four years building, and one of the best things about the kitchen is the “kickspace heater” under the sink cabinet. We had it put in because there wasn’t enough baseboard area for the baseboard radiators that heat the rest of the house. They’re fired by hot water from our wood/oil boiler.

    One of these would let you do the dishes and warm up your feet at the same time.


  18. DirkH says:

    See here for more

    “Radiation from mammals and the living human body: Mammals at roughly 300 K emit peak radiation at 3 thousand µm K / 300 K = 10 µm, in the far infrared. This is therefore the range of infrared wavelengths that pit viper snakes and passive IR cameras must sense.”


  19. Cybrerzombie says:


    Peripheral Neuropathy?

  20. philjourdan says:

    @E.M. That is the difference between us. I am just not as attentive to those things as I should be (and probably why I bleed all over the place since I do not notice I have cut myself until someone yells at me to stop bleeding on the carpet).

  21. Tim says:

    Here in the UK last year I was getting fed up with the light out put and performance of CFL lighting. The kitchen and bathroom had 6 and 4 array halogen GU10 bulbs respectively, each bulb 50Watts. As an experiment I replaced one bulb with a 5 Watt LED. To my surprise it was brighter and with a wider beam than the Halogen. I have replaced nearly all lighting now with LEDs. They are expensive, but if they live up to their advertised life they will be cheaper in the long run. 2 bulbs failed and were replaced under warranty. The outside floodlight is now 30 Watts instead of 300Watts.
    I know this won’t warm your feet, but it makes my bank balance much healthier.


  22. Tim Clark says:

    I suggest ceiling fans. At the lowest level I estimate little temp difference between floor and ceiling. but I’ve never walked on the ceiling.
    I have a rather large house (3,000+) with a walk-out basement where the kids stayed. My wife and I rarely go down there now that the kids are gone because we really have no need, even though it cost a sh1tload to finish nicely. So I have all the ceiling vents shut. But I go there on occasion (football, movies) because the HD flat screen is there (O’Reilly is ok on the old one upstairs). The south facing half-windows let in too much cold south Kansas winter wind, so I put an electric gas-filled heater downstairs on some tiles between the bar and bath so I wouldn’t have to open the vents and wait for the gas furnace to heat the place up. Also, I had to warm the upstairs too much before the basement warmed. I noticed over time that on those occasions I would turn the electric gas filled heater on downstairs, it seemed the upstairs tiled kitchen floor was warmer when I went up for a little liquid refreshment (alright-a lot). And that the furnace didn’t run as much. Seemed reasonable, hot air rises, I should have known. But I decided to do a little math on the cost. I used the first four years without the electric heater versus the last five, corrected for absolute temperature and with a record of when I turned on the electric heater and when not, etc. This was not a rigid study obviously.
    It turns out that it is cheaper to heat the house with the combination of a single basement electric heater and furnace, than furnace alone, even when we are not downstairs. But surprisingly, the differential is greater when compared to opening the basement vents for furnace heat. And we get the benefits of no cold feet upstairs, and what seems to be a little less variation in temperature. So when it gets about 40 degrees outside nighttime, the electric heats stays on. I’m guessing that the warmer air being sucked into the furnace via the downstairs air intake (positioned close to the oil heater) has something to do with it. It could also be that the furnace is just an inefficient piece of builders grade crap.

  23. Svend Ferdinandsen says:

    Part of the problem is Boltzmann and heat loss from the floor to the ground or whatever is under the floor of lower temperature. At normal indoor temperature the ceiling will radiate ~400W/m2 and this radiation changes with 6W for each kelvin change.
    If you loose 12W/m2 from the floor it will be 2K colder than the ceiling to keep balance in the radiation budget, and such a difference is very easy felt.
    Convection of cold air on the floor will make it worse as hot air would make it better, but insulation of the floor is a good solution anyway.
    I realized this connection in an old cabin in Nederland, CO during christmas with -10C outside and hardly any insulation under the floor. The difference from ceiling to floor could be 10C, and then you can talk of cold feets.

  24. philjourdan says:

    @Cyberzombie – I have thought of that, especially since my Uncle is famous for his work with Leprosy. But it is not like i do not feel it, just that I do not pay any attention to it. I guess it just is not a big enough bother to occupy my mind.

  25. DirkH says:

    Svend Ferdinandsen says:
    10 January 2013 at 8:33 pm
    “Part of the problem is Boltzmann and heat loss from the floor to the ground or whatever is under the floor of lower temperature. At normal indoor temperature the ceiling will radiate ~400W/m2 and this radiation changes with 6W for each kelvin change.
    If you loose 12W/m2 from the floor it will be 2K colder than the ceiling to keep balance in the radiation budget, and such a difference is very easy felt.”

    Are you assuming your floor and your ceiling are both perfect or equally imperfect blackbodies?


  26. Paul Hanlon says:

    A couple of years ago, I installed an Echelon Smartserver to control a CHP plant in a very large commercial greenhouse farm. The greenhouses were climate controlled with enhanced CO2 levels (around 12-1500 ppm, or about two doublings). The biggest expense was heating so any optimizing they could do in this area went straight to the bottom line.

    You would think with all the extra CO2 plus all the humidity from the plants (for some runaway greenhouse goodness), that there would be some difference between the CO2 enhanced houses and the non CO2 enhanced, but there wasn’t a measurable difference. The heating still had to go on at the same time at nighttime.

    Things that make you go Hmmm :-).

  27. Svend Ferdinandsen says:

    DirkH says:
    “Are you assuming your floor and your ceiling are both perfect or equally imperfect blackbodies?”
    Yes more or less. Most materials are close to black at the wavelengths involved.
    Radiation is not the only explanation, but it explains a great part of the difference. You would need a great deal of air circulation to accomplish the same heat transport as the radiation does without noise and blowing air.

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