4 ms·

There were cholera epidemics in the 19th century, until we realized we shouldn't drink contaminated water. In cities such as London, this required major infrast

There were cholera epidemics in the 19th century, until we realized we shouldn't drink contaminated water. In cities such as London, this required major infrastructure investments. We're just realizing we shouldn't breathe contaminated air, and we're just realizing that we need to make infrastructure investments. CO2 is a good proxy for infectious disease transmission risk. We breathe out CO2 as we spread pathogens. Outside air is just above 400ppm (higher with auto exhaust) and architects aimed for 600ppm before the pandemic. As one approaches CO2 levels closer to outside air, infectious disease transmission plummets. To balance ventilation with energy costs (and avoid accelerating global warming) one needs heat exchangers that can't easily be retrofitted into an existing building. Munger Hall could dodge all the bad publicity about fake windows if it sports a "next pandemic ready" ventilation system out of the blocks. In my experience sitting on building committees, architects are better at original visuals than original engineering. When a Spanish village restores ancient stone huts for tourists, they run DC wiring for LED lights. When I ask if our new building will have DC wiring for LED lights, rather than a cheap, inefficient transformer in every bulb, architects just stare back at me, deer in the headlights. So I'm not hopeful that a radical reworking of our infrastructure will originate with architects. Our building wasn't going to have windows that opened, till I suggested the building would be usable parts of the year even if the central air failed. I was assured it would never fail. The central air in the previous building failed the next week; I was never implicated. Then our administration overruled the architects and put in office windows. People teased me that I cost us a "this building pees spring water" green certification. Then the pandemic, and I was a hero.

sbierwagen 5y ago
>Outside air is just above 400ppm In 2015 it was, sure. We'll probably hit a seasonal peak of 420ppm next year. https://gml.noaa.gov/ccgg/trends/ https://gml.noaa.gov/ccgg/trends/ RCP8.5 has us at 1000ppm by the end of the century. By then outside air ventilation will mostly be needed to keep people in meeting rooms from putting themselves into a coma.
kixiQu 5y ago
> just realizing we shouldn't breathe contaminated air Well.... https://www.bloomberg.com/news/articles/2020-08-05/the-curious-history-of-steam-heat-and-pandemics https://www.bloomberg.com/news/articles/2020-08-05/the-curio...
- salawat 5y ago
  Hahahahahaha. This is exactly the type of information that gets lost between generations that makes past decisions make sense. It's why I ferverently collect older academic/engineering literature. Not necessarily for the equations, but for some of the context around the problems and challenges of the time we no longer think about because they are "already solved". Everyone moans about radiators once you start sealing up windows to be more green. Surprise! They were designed with the inefficiency of having an open window in mind for health and ventilation purposes since the turn of the century! Of course you end up with problems when you violate a functional invariant!
pasabagi 5y ago
> if our new building will have DC wiring for LED lights, rather than a cheap, inefficient transformer in every bulb, This blows my mind too. I expect it's coming, though: the cables would be cheaper, and if there's one driver of change in construction, it's cost. Another question is, would it be a straight improvement? I think transformers are typically very efficient, and I could imagine the losses from running a lower voltage through a long line might be greater.
- nucleardog 5y ago
  Running DC typically requires much higher gauge wire. To keep under a 10% voltage drop (which is a _lot_), our current 15A branch circuits on 14g wire would be limited to about 10ft away from the transformer. You could make it to ~30ft on existing wiring as long as you kept draw under 5A. That’s ~60W and enough to power all of 5 pretty anemic 12V bulbs. If you actually need something like a 60ft run from your transformer and 15A to play with, you’re going to be looking more towards something like 6AWG. If you want to keep under 3% voltage drop you’d be looking towards 2AWG. 14AWG 2-wire is something like $0.35/ft. 6AWG 2-wire is like $0.75/ft. 2AWG 2-wire is coming up on $3/ft. There’s a reason we use AC for power distribution rather than DC.
  - pasabagi 5y ago
    Does AC differ significantly to DC when it comes to wire gauge? If so, why? I thought wire heating was simply a function of amps? While I think 12V would be too low, I think there's also a happier medium than 120/220V. Something like 50V is nice because you're very unlikely to get an electric shock, while taking advantage of the fact the average LED current draw is like 1 fifth of an incandescent.
  - accountofme 5y ago
    Is this assuming that you keep the voltage low? Say at 12V? Wouldn't we push the voltage to maximise the power pushed and minimise the resistive losses?
    - nucleardog 5y ago
ryantgtg 5y ago
Don’t windows that open give you LEED points? Why would open windows cost you green cred?
pbronez 5y ago
> Munger Hall could dodge all the bad publicity about fake windows if it sports a "next pandemic ready" ventilation system out of the blocks. Apparently it will: "[The building] will provide built-in social distancing as required by COVID. Fresh air, the architect insisted, will be vented into all rooms at twice the rate mandated by existing building codes and will be off-gassed directly to the atmosphere without any transfer to other rooms in the dorm."

sbierwagen 5y ago

>Outside air is just above 400ppm In 2015 it was, sure. We'll probably hit a seasonal peak of 420ppm next year. https://gml.noaa.gov/ccgg/trends/ https://gml.noaa.gov/ccgg/trends/ RCP8.5 has us at 1000ppm by the end of the century. By then outside air ventilation will mostly be needed to keep people in meeting rooms from putting themselves into a coma.

kixiQu 5y ago

> just realizing we shouldn't breathe contaminated air Well.... https://www.bloomberg.com/news/articles/2020-08-05/the-curious-history-of-steam-heat-and-pandemics https://www.bloomberg.com/news/articles/2020-08-05/the-curio...

salawat 5y ago
Hahahahahaha. This is exactly the type of information that gets lost between generations that makes past decisions make sense. It's why I ferverently collect older academic/engineering literature. Not necessarily for the equations, but for some of the context around the problems and challenges of the time we no longer think about because they are "already solved". Everyone moans about radiators once you start sealing up windows to be more green. Surprise! They were designed with the inefficiency of having an open window in mind for health and ventilation purposes since the turn of the century! Of course you end up with problems when you violate a functional invariant!

pasabagi 5y ago

> if our new building will have DC wiring for LED lights, rather than a cheap, inefficient transformer in every bulb, This blows my mind too. I expect it's coming, though: the cables would be cheaper, and if there's one driver of change in construction, it's cost. Another question is, would it be a straight improvement? I think transformers are typically very efficient, and I could imagine the losses from running a lower voltage through a long line might be greater.

nucleardog 5y ago
Running DC typically requires much higher gauge wire. To keep under a 10% voltage drop (which is a _lot_), our current 15A branch circuits on 14g wire would be limited to about 10ft away from the transformer. You could make it to ~30ft on existing wiring as long as you kept draw under 5A. That’s ~60W and enough to power all of 5 pretty anemic 12V bulbs. If you actually need something like a 60ft run from your transformer and 15A to play with, you’re going to be looking more towards something like 6AWG. If you want to keep under 3% voltage drop you’d be looking towards 2AWG. 14AWG 2-wire is something like $0.35/ft. 6AWG 2-wire is like $0.75/ft. 2AWG 2-wire is coming up on $3/ft. There’s a reason we use AC for power distribution rather than DC.
- pasabagi 5y ago
  Does AC differ significantly to DC when it comes to wire gauge? If so, why? I thought wire heating was simply a function of amps? While I think 12V would be too low, I think there's also a happier medium than 120/220V. Something like 50V is nice because you're very unlikely to get an electric shock, while taking advantage of the fact the average LED current draw is like 1 fifth of an incandescent.
- accountofme 5y ago
  Is this assuming that you keep the voltage low? Say at 12V? Wouldn't we push the voltage to maximise the power pushed and minimise the resistive losses?
  - nucleardog 5y ago

ryantgtg 5y ago

Don’t windows that open give you LEED points? Why would open windows cost you green cred?

pbronez 5y ago

> Munger Hall could dodge all the bad publicity about fake windows if it sports a "next pandemic ready" ventilation system out of the blocks. Apparently it will: "[The building] will provide built-in social distancing as required by COVID. Fresh air, the architect insisted, will be vented into all rooms at twice the rate mandated by existing building codes and will be off-gassed directly to the atmosphere without any transfer to other rooms in the dorm."