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There’s a saying, earthquakes don’t kill people—buildings kill people when they collapse. In the open air on a grassland, covid won’t kill a population. The de

There’s a saying, earthquakes don’t kill people—buildings kill people when they collapse. In the open air on a grassland, covid won’t kill a population. The design of our hermetically sealed buildings is what’s killing us. Back in the 1970s the air outside was full of lead and smog, so the safest thing too was completely seal all office buildings. Today the air inside probably contains more hydrocarbons (from volatile organic compounds offgassing from carpets and furniture) so the best thing to do is vent air to the outside and keep the windows open (assuming you live in a mild climate) Of course, that flies in the face of all efforts to make things green…which involve better insulation, sealing windows against leaks, more air filtration systems and etc. Here in Canada the temperature drops like 5 or 10 degrees when you walk into a forest. I’ve stepped into a traditional mud hut and experienced a similar cooling effect. The common denominator is that both environments have a high surface area compared to say concrete. This acts as an efficient radiator so that when water to evaporates it removes heat. In low humidity climates this is one way to reduce cooling demands. Beyond that if we cool micro zones or interstate cooling into clothing itself through hoses or something that might be the next step in efficiency…until it gives birth to the next problem.

ddxxdd 5y ago
>Of course, that flies in the face of all efforts to make things green…which involve better insulation, sealing windows against leaks, more air filtration systems and etc. If anyone has a half-hour of time to waste, you can look into the science of "countercurrent heat exchangers". It's fascinating to see how 2 pipes of air current switch temperatures when they're in contact and moving in opposite directions. So if you want to be green AND have fresh air constantly circulating through a building, then forcing the warm inside air to pass by the cold outside air as they leave/enter the building can lead to somewhere around 95% energy recovery. Add in a humidifier to the incoming air, and you'll have a comfortable room with humidity that will attach to airborne droplets, prevent evaporative release of a raw airborne virus, and help pull the droplet down to the ground via gravity.
- rightbyte 5y ago
  > It's fascinating to see how 2 pipes of air current switch temperatures when they're in contact and moving in opposite directions. Shouldn't the air ideally move in the same direction?
  - ddxxdd 5y ago
    Nope, because they will both end up at the same temperature, namely, the average temperature halfway between the two previous temperatures. In a countercurrent heat exchanger, the hot air will get colder and colder until it is at the same temperature as the cold air, and the cold air will get hotter and hotter until it is the same temperature as the hot air. This is because the hot air is not warming up the same air molecules that it relies on to cool down, and the cold air is not cooling down the same air molecules that it relies on to warm up. Each current of air gives up a part of their heat/coldness, becomes colder/hotter, and then moves towards a section of pipe that's even colder/hotter than the previous section of pipe. A picture is worth a thousand words, although it takes some staring and studying before the concept finally clicks: https://en.wikipedia.org/wiki/Countercurrent_exchange#/media/File:Comparison_of_con-_and_counter-current_flow_exchange.jpg https://en.wikipedia.org/wiki/Countercurrent_exchange#/media...
    - rightbyte 5y ago
      Ah ye thank you makes sense.
  - deleted 5y ago
    [deleted]
  - mrow84 5y ago
    There is a diagram illustrating why not in the wikipedia article: https://en.wikipedia.org/wiki/Countercurrent_exchange https://en.wikipedia.org/wiki/Countercurrent_exchange
- londons_explore 5y ago
  Wikipedia claims "Heat recovery systems typically recover about 60–95% of the heat in exhaust air". But even recovering 95% of heat isn't exactly great. If you live in Canada and have a 2600 sq ft house with 8 ft ceilings and 10 changes of air per hour, and the indoors is 70F and outdoors is 0F, thats 2600810 cubic feet of air/ per hour, or 12000 BTU/hr. That means you are more than doubling your heating costs compared to sealing the building and just having conductive losses through the walls. This is true for most climates - even the best energy recovery systems still double heating/cooling costs compared to having barely any fresh air.
legulere 5y ago
With a controlled ventilation system you have better indoor air than with leaky old houses and it's also more energy efficient.

ddxxdd 5y ago

>Of course, that flies in the face of all efforts to make things green…which involve better insulation, sealing windows against leaks, more air filtration systems and etc. If anyone has a half-hour of time to waste, you can look into the science of "countercurrent heat exchangers". It's fascinating to see how 2 pipes of air current switch temperatures when they're in contact and moving in opposite directions. So if you want to be green AND have fresh air constantly circulating through a building, then forcing the warm inside air to pass by the cold outside air as they leave/enter the building can lead to somewhere around 95% energy recovery. Add in a humidifier to the incoming air, and you'll have a comfortable room with humidity that will attach to airborne droplets, prevent evaporative release of a raw airborne virus, and help pull the droplet down to the ground via gravity.

rightbyte 5y ago
> It's fascinating to see how 2 pipes of air current switch temperatures when they're in contact and moving in opposite directions. Shouldn't the air ideally move in the same direction?
- ddxxdd 5y ago
  Nope, because they will both end up at the same temperature, namely, the average temperature halfway between the two previous temperatures. In a countercurrent heat exchanger, the hot air will get colder and colder until it is at the same temperature as the cold air, and the cold air will get hotter and hotter until it is the same temperature as the hot air. This is because the hot air is not warming up the same air molecules that it relies on to cool down, and the cold air is not cooling down the same air molecules that it relies on to warm up. Each current of air gives up a part of their heat/coldness, becomes colder/hotter, and then moves towards a section of pipe that's even colder/hotter than the previous section of pipe. A picture is worth a thousand words, although it takes some staring and studying before the concept finally clicks: https://en.wikipedia.org/wiki/Countercurrent_exchange#/media/File:Comparison_of_con-_and_counter-current_flow_exchange.jpg https://en.wikipedia.org/wiki/Countercurrent_exchange#/media...
  - rightbyte 5y ago
    Ah ye thank you makes sense.
- deleted 5y ago
  [deleted]
- mrow84 5y ago
  There is a diagram illustrating why not in the wikipedia article: https://en.wikipedia.org/wiki/Countercurrent_exchange https://en.wikipedia.org/wiki/Countercurrent_exchange
londons_explore 5y ago
Wikipedia claims "Heat recovery systems typically recover about 60–95% of the heat in exhaust air". But even recovering 95% of heat isn't exactly great. If you live in Canada and have a 2600 sq ft house with 8 ft ceilings and 10 changes of air per hour, and the indoors is 70F and outdoors is 0F, thats 2600810 cubic feet of air/ per hour, or 12000 BTU/hr. That means you are more than doubling your heating costs compared to sealing the building and just having conductive losses through the walls. This is true for most climates - even the best energy recovery systems still double heating/cooling costs compared to having barely any fresh air.

legulere 5y ago

With a controlled ventilation system you have better indoor air than with leaky old houses and it's also more energy efficient.