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> It’s how the rich got their fresh air back in the day. Fuel bills were not a concern. I once had a tour in a now-empty former Siemens office building in Muni

by rob74 5y ago

> It’s how the rich got their fresh air back in the day. Fuel bills were not a concern. I once had a tour in a now-empty former Siemens office building in Munich (https://translate.google.com/translate?hl=&sl=de&tl=en&u=https%3A%2F%2Fde.wikipedia.org%2Fwiki%2FSiemens-Hochhaus_(M%C3%BCnchen) https://translate.google.com/translate?hl=&sl=de&tl=en&u=htt...) built in the sixties. This 75 meter highrise had the same kind of heating: cold air was sucked in through a mushroom-shaped structure at the side of the building, heated electrically in a huge room in the basement, and piped into every office room where it came in through vents under the windows. The "used" warm air was then collected and pumped straight outside again. Fuel/electricity bills were apparently not a concern for Siemens either - this was the pre-oil crisis era, plus they were a major player in the nuclear industry...

TeMPOraL 5y ago
I thought this is the standard way to do HVAC in large buildings: you pull in and condition the outside air, push it through ducts ("supply flow") to every room in the building, then collect the "used" air through separate ducting ("return flow") and pull it to the basement, reclaim some of the energy, and then push it out. (Or maybe it was? It's increasingly common to see office buildings with lots of AC units on the side walls - but I suspect that's HVAC equivalent of Conway's law: where every floor may have a different owner, it makes less sense to invest in central HVAC.) Other than ensuring heat pumps are involved at entry/exit stage, I'm not sure how you could make it more fuel-conservative. Some wins can be had if you put enough smarts in the ducts, but overall, there's a price you have to pay for near-total control over the air. Also, the article seems to be implying that ducts were (still are!) made from metal because it was cheap, and nobody cared about energy leakage. But it's not that - the ducts are made from metal because of friction. Over the length of the ducting, inner wall roughness adds up into static pressure your blowers will have to fight - so you want to minimize that, to save on energy use and wear.
- rob74 5y ago
  The guy who organized the tour didn't mention anything about a heat pump - and he was the developer who had bought the building, so I guess he would have known. Heat pumps were invented much earlier, but didn't become commonplace for this purpose until after the oil crisis. Plus, IIRC the system was only HV without the AC. With added AC and heat pumps to reduce the heat loss, it definitely makes more sense...
- sokoloff 5y ago
  It’s not exactly that way, though it might rhyme with that. I think it’s more accurate to think of “air is taken from conditioned spaces via return ducts to the air handlers, where it is conditioned (filtered, heated, cooled, re or de-humidified) and then supplied via vents; separately, there may be active exchange of fresh air from outside via an HRV/ERV to ensure adequate air changes. (Many older buildings rely on leakage for the latter purpose, sometimes supported by using inside air for combustion [which will draw outside air in].)” The difference is that the demand for fresh air is largely independent of the temperature needs of the space, so you want to decouple the fresh air supply from the temperature change. (You don’t want a massive increase in fresh air on the coldest or hottest/most humid day.)

by rob74 5y ago

TeMPOraL 5y ago

I thought this is the standard way to do HVAC in large buildings: you pull in and condition the outside air, push it through ducts ("supply flow") to every room in the building, then collect the "used" air through separate ducting ("return flow") and pull it to the basement, reclaim some of the energy, and then push it out. (Or maybe it was? It's increasingly common to see office buildings with lots of AC units on the side walls - but I suspect that's HVAC equivalent of Conway's law: where every floor may have a different owner, it makes less sense to invest in central HVAC.) Other than ensuring heat pumps are involved at entry/exit stage, I'm not sure how you could make it more fuel-conservative. Some wins can be had if you put enough smarts in the ducts, but overall, there's a price you have to pay for near-total control over the air. Also, the article seems to be implying that ducts were (still are!) made from metal because it was cheap, and nobody cared about energy leakage. But it's not that - the ducts are made from metal because of friction. Over the length of the ducting, inner wall roughness adds up into static pressure your blowers will have to fight - so you want to minimize that, to save on energy use and wear.

rob74 5y ago
The guy who organized the tour didn't mention anything about a heat pump - and he was the developer who had bought the building, so I guess he would have known. Heat pumps were invented much earlier, but didn't become commonplace for this purpose until after the oil crisis. Plus, IIRC the system was only HV without the AC. With added AC and heat pumps to reduce the heat loss, it definitely makes more sense...
sokoloff 5y ago
It’s not exactly that way, though it might rhyme with that. I think it’s more accurate to think of “air is taken from conditioned spaces via return ducts to the air handlers, where it is conditioned (filtered, heated, cooled, re or de-humidified) and then supplied via vents; separately, there may be active exchange of fresh air from outside via an HRV/ERV to ensure adequate air changes. (Many older buildings rely on leakage for the latter purpose, sometimes supported by using inside air for combustion [which will draw outside air in].)” The difference is that the demand for fresh air is largely independent of the temperature needs of the space, so you want to decouple the fresh air supply from the temperature change. (You don’t want a massive increase in fresh air on the coldest or hottest/most humid day.)