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HVAC engineer here. Correct - and the reason that ventilation is currently limited in buildings is to reduce energy loss. Exhausting warm air in winter or cool

by tjmc 5y ago

HVAC engineer here. Correct - and the reason that ventilation is currently limited in buildings is to reduce energy loss. Exhausting warm air in winter or cool air in summer is enormously resource intensive for a building. Depending on the building configuration, you can reclaim some but not all of that energy by using heat exchangers, where the exhaust and supply air streams exchange heat without mixing but then you impose an energy penalty via increased pressure on the ventilation fans in mild conditions when the heat exchange is of less benefit. So all the standards and codes are designed around reducing unnecessary ventilation and frankly, there's been very little consideration of the health implications until COVID hit.

edejong 5y ago
If you would be building a new house and willing to spend double the usual on HVAC, what would your focus be on?
- tjmc 5y ago
  The perhaps non-intuitive answer is - everything that reduces the need for HVAC. I'd be looking at things like passive solar design so windows are shaded in summer but let sunlight in for heat in winter. Very good insulation and building sealing. Double glazing (possibly triple if you're in a very cold climate). Thermal mass in the right places for temperature stablity. On the HVAC side, you want a system with a high CoP and I'd probably be looking at some form of energy recovery on the ventilation side.
  - eecc 5y ago
    Yup, very much so: https://www.treehugger.com/praise-dumb-box-4853131 https://www.treehugger.com/praise-dumb-box-4853131 I live in a relatively new building in NL, where many of these configurations are applied and on its own it won’t go lower than 21C in winter and 25C in summer. Thick walls, thick anhydrous cement floor layer for insulation (although I think it’s also meant to give the option to implement floor heating), _external_ blinds on the South side. I simply can’t justify a smart thermostat/radiator valve build, despite my inside nerd constantly whispering I should. Only downside is the heat exchanger air recirculator: it dries the air terribly in winter. You need a humidifier to avoid getting parched skin and mucosa.
  - graeme 5y ago
    What if you wanted good ventilation/co2 levels?
    - maxerickson 5y ago
      With modern construction, active ventilation is a requirement. So sizing that for the intended turnover would probably be all you would need to do.
  - quercusa 5y ago
    > everything that reduces the need for HVAC This is the answer! Even more important than insulation is air sealing, so you keep the conditioned air inside. I've learned an enormous amount about building efficiency from https://www.greenbuildingadvisor.com/ https://www.greenbuildingadvisor.com/ and https://www.energyvanguard.com/ https://www.energyvanguard.com/
- hellbannedguy 5y ago
  If you are in a temperate climate, like The Bay Area, looking into hydronic heating. I installed it, and would never go back to forced air. For some reason, it's not popular on the west coast. It's so simple, a DIY'er could do the instal. My energy bill is down, and allergies are better. (I've noticed every store I have been in has forced HVAC, and I have a weird feeling forced air spread viruses. Plus--most retail stores have old systems. They might have slapped in some high mir filters, but I doubt they help with anything on old leaky systems. (To those interested in hydronic heating, buy Modern Hydronics, by Stegenthal? I'm too lazy to look up his last name, but his book is used as text books.
  - rocqua 5y ago
    For anyone else wondering what hydronic heating is, it's using warm water as your main heat source. Either using radiators, or tubing in the floor to heat a room. This contrasts against the more common American method of using hot air to heat a home. I believe air heating is more common in the US because AC systems already require the relevant air ducting, so it's easier to install. Meanwhile here in NL airconditioning is very rare, and 95% of people use a gas fired water heater and metal radidators in rooms for heat distribution.
    - baq 5y ago
      i would go as far as to say that nobody in continental europe knows the term 'hydronic', it's just heating, maybe central heating.
  - PoignardAzur 5y ago
    TIL: - The term hydronic heating. - That most Americans don't have hydronic heating. That's so weird, here in France radiators are just ubiquitous. This is the detachable showerhead thing all over again. How do you people survive like that? You're supposed to be the highest GDP country in the world!
    - kasey_junk 5y ago
      It’s because most AC systems require forced air, so hydronic is a second system. You’ll find hydronics in expensive houses that can justify the double expense or in colder climates where the heating benefits are more important than AC. Also everyplace I’ve lived in the last 25 years has had detachable showerheads.
hvidgaard 5y ago
Modern ventilation hardware can reclaim between 85-95% (claimed, but tested and verified). You do not need to run it full power, just a constant optimized flow and only when people are actually in the rooms. I'm relatively sure that the cost is less than heating/cooling a poorly insulated house.
- deleted 5y ago
  [deleted]

by tjmc 5y ago

edejong 5y ago

If you would be building a new house and willing to spend double the usual on HVAC, what would your focus be on?

tjmc 5y ago
The perhaps non-intuitive answer is - everything that reduces the need for HVAC. I'd be looking at things like passive solar design so windows are shaded in summer but let sunlight in for heat in winter. Very good insulation and building sealing. Double glazing (possibly triple if you're in a very cold climate). Thermal mass in the right places for temperature stablity. On the HVAC side, you want a system with a high CoP and I'd probably be looking at some form of energy recovery on the ventilation side.
- eecc 5y ago
  Yup, very much so: https://www.treehugger.com/praise-dumb-box-4853131 https://www.treehugger.com/praise-dumb-box-4853131 I live in a relatively new building in NL, where many of these configurations are applied and on its own it won’t go lower than 21C in winter and 25C in summer. Thick walls, thick anhydrous cement floor layer for insulation (although I think it’s also meant to give the option to implement floor heating), _external_ blinds on the South side. I simply can’t justify a smart thermostat/radiator valve build, despite my inside nerd constantly whispering I should. Only downside is the heat exchanger air recirculator: it dries the air terribly in winter. You need a humidifier to avoid getting parched skin and mucosa.
- graeme 5y ago
  What if you wanted good ventilation/co2 levels?
  - maxerickson 5y ago
    With modern construction, active ventilation is a requirement. So sizing that for the intended turnover would probably be all you would need to do.
- quercusa 5y ago
  > everything that reduces the need for HVAC This is the answer! Even more important than insulation is air sealing, so you keep the conditioned air inside. I've learned an enormous amount about building efficiency from https://www.greenbuildingadvisor.com/ https://www.greenbuildingadvisor.com/ and https://www.energyvanguard.com/ https://www.energyvanguard.com/
hellbannedguy 5y ago
If you are in a temperate climate, like The Bay Area, looking into hydronic heating. I installed it, and would never go back to forced air. For some reason, it's not popular on the west coast. It's so simple, a DIY'er could do the instal. My energy bill is down, and allergies are better. (I've noticed every store I have been in has forced HVAC, and I have a weird feeling forced air spread viruses. Plus--most retail stores have old systems. They might have slapped in some high mir filters, but I doubt they help with anything on old leaky systems. (To those interested in hydronic heating, buy Modern Hydronics, by Stegenthal? I'm too lazy to look up his last name, but his book is used as text books.
- rocqua 5y ago
  For anyone else wondering what hydronic heating is, it's using warm water as your main heat source. Either using radiators, or tubing in the floor to heat a room. This contrasts against the more common American method of using hot air to heat a home. I believe air heating is more common in the US because AC systems already require the relevant air ducting, so it's easier to install. Meanwhile here in NL airconditioning is very rare, and 95% of people use a gas fired water heater and metal radidators in rooms for heat distribution.
  - baq 5y ago
    i would go as far as to say that nobody in continental europe knows the term 'hydronic', it's just heating, maybe central heating.
- PoignardAzur 5y ago
  TIL: - The term hydronic heating. - That most Americans don't have hydronic heating. That's so weird, here in France radiators are just ubiquitous. This is the detachable showerhead thing all over again. How do you people survive like that? You're supposed to be the highest GDP country in the world!
  - kasey_junk 5y ago
    It’s because most AC systems require forced air, so hydronic is a second system. You’ll find hydronics in expensive houses that can justify the double expense or in colder climates where the heating benefits are more important than AC. Also everyplace I’ve lived in the last 25 years has had detachable showerheads.

hvidgaard 5y ago

Modern ventilation hardware can reclaim between 85-95% (claimed, but tested and verified). You do not need to run it full power, just a constant optimized flow and only when people are actually in the rooms. I'm relatively sure that the cost is less than heating/cooling a poorly insulated house.

deleted 5y ago
[deleted]