9 ms·

23% ish. It's not naive. Going to "pure" building science (I studied this in uni) the formula for the building heat loss is Q=U.A.dT where dT is the temperatur

• brudgers 5y ago
  In the US, heating energy loads are calculated on degree-days. This captures the expected dT on days when heating is required and ignores days when heating is not used. In the summer for example... ...except in the US cooling is also common so it actually captures both heating and cooling and involves multiple energy sources in many locations...which brings up that degree-days are highly variable at the local level -- consider the difference between Norway and Greece in the EU. degree-day https://www.eia.gov/energyexplained/units-and-calculators/degree-days.php https://www.eia.gov/energyexplained/units-and-calculators/de...
  • fennecfoxen 5y ago
    US figures are available which can tell you both heating-degree-days and cooling-degree-days.
  • japanuspus 5y ago
    Same in Europe, at least in Denmark. Source: my dad is a civil engineer who has been doing renewables since the oil crisis in the 1970’es.
  • gnu8 5y ago
    What technology are we missing to be able to ship heat from warm houses to cool houses?
• hkt 5y ago
  Don't forget hot water bottles. Excellent recent post from Low Tech Magazine on this: https://solar.lowtechmagazine.com/2022/01/the-revenge-of-the-hot-water-bottle.html https://solar.lowtechmagazine.com/2022/01/the-revenge-of-the... tl;dr is that heating people rather than spaces is a great idea with much more mileage than we give it credit for.
  • Earw0rm 5y ago
    This. It's widely accepted that ebikes are some of the most energy efficient personal transport possible, because they're moving so little vehicle mass relative to passenger payload. Just 250 watts can give you rapid enough point to point mobility for trips up to 10 miles or so. In the same way, heating and insulating people is vastly more efficient than heating air and brick walls. 100w of active electric heating together with a couple of layers of clothing is plenty to keep most people pretty comfortable at an ambient temperature of 14-15c.
  • turtlebits 5y ago
    Electric blankets are great too. The model I have only consumes 60W.
  • appleiigs 5y ago
    I'll try using one as a wrist rest. In a cold room I can dress warm, but can't type with gloves on. The Jayne Mansfield hot water bottle would warm me up in more ways than one!
• WithinReason 5y ago
  You can't use the average. Example: Let's say for half year the average temperature is 11°C and for half year it's 31°C. That gives an average temp of 21°C and a δT of 0, even though you would still need to heat for half a year.
  • disiplus 5y ago
    i assume the 5C average is the average for the heating season, not for the whole year.
    • WithinReason 5y ago
      Then you have the day-night cycle
• driverdan 5y ago
  > Also you may risk giving more people diseases This is an old wife's tale. Especially at 18C. No one is going to be getting diseases.
  • dpatru 5y ago
    I get a runny nose if I get cold. Same for my children. From an energy perspective, this make sense. If the body is expending more energy trying to get warm or not get cold, it may not have the necessary energy to fight off germs. Also, the immune system works better hot, aka fever. Cooling the body can be expected to suppress the immune system. Before you dismiss proverbs (old wives’ tales), consider that they could persist because they’re true.
    • leereeves 5y ago
      > I get a runny nose if I get cold. I was curious, so I looked it up, and according to [1] and [2], that's a natural reaction to help the nose turn cold, dry air into warm, moist air. "When cold air enters the nose, it stimulates the sensory nerves within the nasal cavity to activate a process via a cholinergic reflex or pathway. It causes the vessels in the nasal cavity to expand and become engorged, leading to congestion and mucus secretion which produces a runny nose. It’s a compensatory mechanism that’s trying to maintain ideal conditions inside the nose by adding humidity and warmth while filtering the air." 1: https://medicine.uq.edu.au/article/2017/10/why-does-your-nose-run-when-its-cold https://medicine.uq.edu.au/article/2017/10/why-does-your-nos... 2: https://wexnermedical.osu.edu/blog/is-the-cold-weather-causing-your-runny-nose https://wexnermedical.osu.edu/blog/is-the-cold-weather-causi...
    • kaba0 5y ago
      I would like to see a source on that, but the human body is orders of magnitude more complex than to reason about things like “it has to expend more energy” and “fever is good”. You could pretty much derive every effect from every input with these low level “conclusions”. We have evidence-based medicine exactly because even when it would seem logical, biology puts a curve on that and the opposite of the intended effect happens.
    • 5y ago
• roughly 5y ago
  I seem to recall running the HVAC system also doing some work to keep the humidity in the building low, and that being factored into building design - that sound right or ring any bells?
  • whiddershins 5y ago
    Shouldn’t be a factor in winter.
• can16358p 5y ago
  > Also you may risk giving more people diseases and reduce cognitive abilities when things get cold. Could you explain this part? This is exactly opposite of what I've seen my entire life.
  • a1371 5y ago
    Yes, many people argue that they function better in the cold. That very well may be true. People's metabolism and feelings are very different. That's taking about what's generally accepted. The body of literature in this field defines a "comfort zone" that spans around and above 20°C. it's been studied that with better comfort there is better attention. Also being cold appears to weaken the immune system.
    • can16358p 5y ago
      Mine and everyone I know's immune system is strengthened, not weakened, by cold. It "appears" to weaken by giving it a run to its knees, but actually making it stronger while doing that. If you expose yourself to more cold, you start never getting ill.
      • seanmcdirmid 5y ago
        Older people have much weaker immune systems that aren’t strengthened when it gets cold. HK lacks central heating, and a bunch of older people died when they had a cold snap that took them down to 5C. If you think your immune system is helped by being cold all the time, southern China during the winter is the place for you! It’s amazing how constantly being continuously exposed to non freezing but still cold room temperatures can really mess up your immune system.
• idoubtit 5y ago
  In my opinion, it is naive. First of all, the average yearly temperature means nothing for indoor heating. Suppose this average is 20°C: it could be half of the year at 5°C and half at 35°. It's even more complex, for instance if cold days and hot days alternate they have very little impact. The heating is mostly needed when the temperature stays low several days in a row. Then, there are external sources of heat, like sun or human heat. They can increase the indoor temperature for a few degrees. I worked for years in an office, facing South, with no heating even when it was freezing outside, and it was okay. Finally, the formula does not imply what you said. In plain words, it means the energy (heat) is proportional to the mass and the temperature difference. The factor depends on the material. So it does mean that increasing the temperature of 13° instead of 16° uses about 23% less energy. But it does not mean that this much energy is needed to keep this temperature inside a building. Suppose that, with an external temperature of 7° (the average for my city for February) an insulated building at 20° would lose 5° a day. Then dT=5 in the formula above. Whereas the same building at 17° would lose 3° per day, so dT=3, a 40% decrease in the energy needed. In my opinion, there are too many factors to give a simple answer. It know it's possible to estimate this for a single building, given a proper model of the weather and sun exposure, but it is hard to generalize from an individual response.
  • hectormalot 5y ago
    your comment about average yearly temperatures is of course correct, but in this case it biases in favour of GP: * It's colder than average today, to reducing the setpoint has more effect vs an annual average. If sun takes part of the heating, then the ratio of dT to gas saved is even bigger. * The formula actually does work that way, maybe you're thinking of a different formula? i.e. Q (flow of heat) is a function of some heat transfer coefficient (U), area (A) and the temperature difference (dT) between inside and outside. So the (simple) correlation between dT and gas consumption to maintain a temperature is linear. This will be influenced by e.g. wind (increases U, therefore gas consumption) and other factors of course. Anyway, it's winter. If there is any time where you can reasonably reduce your gas consumption by lowering the thermostat, it's today. In fact, I'll try this now and see if it works. Maybe time to start a movement. (Also note that residential heating and office account for roughly a third of gas consumption in e.g. the Netherlands. Reducing that by 20% is still 7% reduction in total, and potentially a 17.5% reduction in Russian gas given the current gas mix)
• ip26 5y ago
  It doesn't help as much in a cold snap though, which is peak gas demand. If it's -25C outside, each degree C is only ~2% change in delta T. I'm all about dialing back the thermostat, but I've also noticed a huge comfort difference between 18C and 19C. Quality of life starts to nosedive for a few percent more saving; it's better to fix up your house.
  • gpm 5y ago
    As I understand it europe has significant gas storage capabilities. The cold snap creates a demand that can't be average out for things like last mile pipelines, but those aren't the limitation. Storage should allow for averaging gas usage over (I think) the whole winter to decide whether or not there is a problem.
• prof-dr-ir 5y ago
  More precisely you say that we would save 23% of our heating expenses. But not all of our heating is from gas, and gas is not exclusively used for heating. So this is only a first step towards answering the original question.
  • whiddershins 5y ago
    Occupied gas heating. Many residences and almost all offices maintain lower setpoint when unoccupied.
• whiddershins 5y ago
  Even if this formula works, this would be 23% of heating consumption when buildings are occupied, not 23% of all heating consumption, and definitely not 23% of all gas usage.
• KolenCh 5y ago
  This is incredibly naive. The only non-naive thing is that it is proportional to ΔT, which is simple Physics. I don’t know why you need to quote building science here. For non naive calculation, one would expect using real world data to estimate the actual weighted average. I mean it is ok to have a naive guesstimate, or to sound better, a Fermi estimate. But for order of magnitude guesstimate, just use 1 sig fig to convey you really don’t have that much confidence. Also I think while providing a ratio is technically answering the question, but people probably expect the absolute scale, in terms of $ or may be a ratio comparing to annual spending (given a country.) I think in short this is not a simple question and we should not pretend it to have simple answer.