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This is why changing out incandescents for CFL's in a heated house does almost nothing for saving energy... and if the heat comes from electricity, nothing for

by lutorm 12y ago

This is why changing out incandescents for CFL's in a heated house does almost nothing for saving energy... and if the heat comes from electricity, nothing for saving money, either.

mangecoeur 12y ago
Wrong. Does plenty to save energy. Reasons: - for half the year, you don't heat but you still light, so you automatically gain savings for that whole period. (also if you have air conditioning, in summer you heat the house with lights then have to cool the air again) - Lights are on the ceiling. Hot air rises. Therefore heat coming from lights does almost nothing to improve your thermal comfort. - If you are heating using gas rather than electricity, it is far more efficient to heat air with energy from the gas boiler than from the electric lighting
- superuser2 12y ago
  This is likely mitigated somewhat if you have good natural light sources. The warmer it is, the less you need to run artificial lights (assuming a "normal" sleep schedule.) Not to say that it makes sense, but still.
- lutorm 12y ago
  If you don't heat, you don't have a heated house. Hence my comment does not apply.
  - lutorm 12y ago
    I wish whoever downvoted this would indicate what part of my comment they disagree with... I said "If A then B", and then the response was "wrong, because if not A then C". Of course it saves energy if you don't heat the house, that's obvious. What's less obvious to many is that it saves much less than you think if you live in a house in Northern Sweden, heated with electric heat (which I happened to grow up in).
- ams6110 12y ago
  What's the energy cost of making a CFL bulb vs. an incandescent? Also since in practice they don't last a lot longer, and are annoyingly dim for the first few minutes, and are considered an hazardous waste when you need to dispose of them, why does it make sense to replace a $0.50 bulb that has none of those issues with a $5.00 bulb that does?
  - roel_v 12y ago
    CFL is crap, use LED lights. Last 20x longer with 1/20th the energy use. Replacing incandescent with CFL is a wash, replacing them with LED is a no-brainer.
    - tempestn 12y ago
      Much more attractive too, if you prefer a redder (more like incandescent) light indoors. Modern LED bulbs are really good.
      - jpindar 12y ago
        You can get LED lights in a variety of color temperatures. You can even get ones like my Phillips Hue bulbs whose color can be adjusted remotely. They aren't cheap but they're a lot of fun!
        tempestn 12y ago
        For sure. I just meant that if you prefer bluer light, you can get that with CFLs, but they can't give you the 'softer' light that we're used to from incandescents, while LEDs can (if that's your preference).
  - mangecoeur 12y ago
    Not sure what you are doing to your CFLs to make them not last longer than incandescent bulbs. I think i've had maybe one CFL break, and that was an early model. LEDs are of course much much more reliable and will most likely outlive you, though personally I don't like this obsession with trying to cram them into traditional light socket formats - I'd like to see something a bit more innovative. They work particularly well as spotlight replacements and ikea have a nice range of innovative designs that don't cram the LEDs too close (which causes heat buildup and reduces efficiency).
bluthru 12y ago
Of course it does. Heating up a hole in your ceiling does not efficiently warm the occupant. You want to introduce heat low and near occupants. Also, changing out multiple incandescents means more manufacturing, more truck deliveries to the store, more manufacturing, etc. vs. using a single LED bulb for two decades. If you live in coal country, then you definitely want to reduce your electrical load and instead rely on a less-bad option of natural gas for warmth.
- lutorm 12y ago
  Most heat from incandescents is infrared radiation, which travels. If you get useful light from the bulb, you also get useful heat. Plenty of rooms are heated with one big, honking radiator, which certainly is no more effective. That said, it's true that some of the heat ends up not being useful (just like a lot of the light from the bulb doesn't either) -- unless there's a heated story above, of course. And I never implied that I think it's a bad idea to get rid of incandescents, for all the other reasons you mention.
  - bluthru 12y ago
    What's the attenuation of the UV from a light bulb in the ceiling?
    - ars 12y ago
      what UV?
      - bluthru 12y ago
        Wups, meant to write IR.
- dredmorbius 12y ago
  Manufacturing and shipping costs of incandescents are very small relative to their energy utilization, as reflected in costs. Your point about fixtures and heat losses through ceilings are actually well-taken. Recessed "can" lighting is actually a huge pathway for heat loss two ways: 1. The radiant heat from bulbs which is transferred into the ceiling and attic spaces, rather than the living space. 2. Other heat flow losses, including often very significant airflow, through the lighting fixtures. Thorsten Chlupp (mentioned elsewhere) includes lighting fixtures among his anti-penetration measures. He also keeps his wiring and plumbing runways along the inner insulates spaces, rather than outside the thermal barrier (with concomitant envelope penetrations).
cma 12y ago
Depends on if you can use a heat pump or not. Heat pumps are more efficient than resistive heating.
- lutorm 12y ago
  True -- if you live in a suitable climate, this is probably the best option of all, regardless of what your electricity comes from.
upofadown 12y ago
During heating season you are correct. During cooling season you end up paying twice for the extra energy consumption of incandescents. So it ends up being climate dependent. In cold countries the savings from changing out incandescents can be a fraction of the savings obtained in hot countries. Where I live you only end up getting half the benefit you would expect from the energy savings alone. If you don't have AC here then the benefit is even lower. There is a current internet legend that the heat from incandescent bulbs does not contribute significantly to building heating. This is entirely wrong for the obvious thermodynamic reason. It's even been tested experimentally with the result that almost all the heat from the bulbs ends up as general heating: http://www.cmhc.ca/odpub/pdf/65830.pdf http://www.cmhc.ca/odpub/pdf/65830.pdf

by lutorm 12y ago

This is why changing out incandescents for CFL's in a heated house does almost nothing for saving energy... and if the heat comes from electricity, nothing for saving money, either.

mangecoeur 12y ago

Wrong. Does plenty to save energy. Reasons: - for half the year, you don't heat but you still light, so you automatically gain savings for that whole period. (also if you have air conditioning, in summer you heat the house with lights then have to cool the air again) - Lights are on the ceiling. Hot air rises. Therefore heat coming from lights does almost nothing to improve your thermal comfort. - If you are heating using gas rather than electricity, it is far more efficient to heat air with energy from the gas boiler than from the electric lighting

superuser2 12y ago
This is likely mitigated somewhat if you have good natural light sources. The warmer it is, the less you need to run artificial lights (assuming a "normal" sleep schedule.) Not to say that it makes sense, but still.
lutorm 12y ago
If you don't heat, you don't have a heated house. Hence my comment does not apply.
- lutorm 12y ago
  I wish whoever downvoted this would indicate what part of my comment they disagree with... I said "If A then B", and then the response was "wrong, because if not A then C". Of course it saves energy if you don't heat the house, that's obvious. What's less obvious to many is that it saves much less than you think if you live in a house in Northern Sweden, heated with electric heat (which I happened to grow up in).
ams6110 12y ago
What's the energy cost of making a CFL bulb vs. an incandescent? Also since in practice they don't last a lot longer, and are annoyingly dim for the first few minutes, and are considered an hazardous waste when you need to dispose of them, why does it make sense to replace a $0.50 bulb that has none of those issues with a $5.00 bulb that does?
- roel_v 12y ago
  CFL is crap, use LED lights. Last 20x longer with 1/20th the energy use. Replacing incandescent with CFL is a wash, replacing them with LED is a no-brainer.
  - tempestn 12y ago
    Much more attractive too, if you prefer a redder (more like incandescent) light indoors. Modern LED bulbs are really good.
    - jpindar 12y ago
      You can get LED lights in a variety of color temperatures. You can even get ones like my Phillips Hue bulbs whose color can be adjusted remotely. They aren't cheap but they're a lot of fun!
      - tempestn 12y ago
        For sure. I just meant that if you prefer bluer light, you can get that with CFLs, but they can't give you the 'softer' light that we're used to from incandescents, while LEDs can (if that's your preference).
- mangecoeur 12y ago
  Not sure what you are doing to your CFLs to make them not last longer than incandescent bulbs. I think i've had maybe one CFL break, and that was an early model. LEDs are of course much much more reliable and will most likely outlive you, though personally I don't like this obsession with trying to cram them into traditional light socket formats - I'd like to see something a bit more innovative. They work particularly well as spotlight replacements and ikea have a nice range of innovative designs that don't cram the LEDs too close (which causes heat buildup and reduces efficiency).

bluthru 12y ago

Of course it does. Heating up a hole in your ceiling does not efficiently warm the occupant. You want to introduce heat low and near occupants. Also, changing out multiple incandescents means more manufacturing, more truck deliveries to the store, more manufacturing, etc. vs. using a single LED bulb for two decades. If you live in coal country, then you definitely want to reduce your electrical load and instead rely on a less-bad option of natural gas for warmth.

lutorm 12y ago
Most heat from incandescents is infrared radiation, which travels. If you get useful light from the bulb, you also get useful heat. Plenty of rooms are heated with one big, honking radiator, which certainly is no more effective. That said, it's true that some of the heat ends up not being useful (just like a lot of the light from the bulb doesn't either) -- unless there's a heated story above, of course. And I never implied that I think it's a bad idea to get rid of incandescents, for all the other reasons you mention.
- bluthru 12y ago
  What's the attenuation of the UV from a light bulb in the ceiling?
  - ars 12y ago
    what UV?
    - bluthru 12y ago
      Wups, meant to write IR.
dredmorbius 12y ago
Manufacturing and shipping costs of incandescents are very small relative to their energy utilization, as reflected in costs. Your point about fixtures and heat losses through ceilings are actually well-taken. Recessed "can" lighting is actually a huge pathway for heat loss two ways: 1. The radiant heat from bulbs which is transferred into the ceiling and attic spaces, rather than the living space. 2. Other heat flow losses, including often very significant airflow, through the lighting fixtures. Thorsten Chlupp (mentioned elsewhere) includes lighting fixtures among his anti-penetration measures. He also keeps his wiring and plumbing runways along the inner insulates spaces, rather than outside the thermal barrier (with concomitant envelope penetrations).

cma 12y ago

Depends on if you can use a heat pump or not. Heat pumps are more efficient than resistive heating.

lutorm 12y ago
True -- if you live in a suitable climate, this is probably the best option of all, regardless of what your electricity comes from.

upofadown 12y ago

During heating season you are correct. During cooling season you end up paying twice for the extra energy consumption of incandescents. So it ends up being climate dependent. In cold countries the savings from changing out incandescents can be a fraction of the savings obtained in hot countries. Where I live you only end up getting half the benefit you would expect from the energy savings alone. If you don't have AC here then the benefit is even lower. There is a current internet legend that the heat from incandescent bulbs does not contribute significantly to building heating. This is entirely wrong for the obvious thermodynamic reason. It's even been tested experimentally with the result that almost all the heat from the bulbs ends up as general heating: http://www.cmhc.ca/odpub/pdf/65830.pdf http://www.cmhc.ca/odpub/pdf/65830.pdf