7 ms·

Cannot escape home insulation and energy efficient ventillation if you want to ensure healthy environment from the humidity point of view. Bathroom, cooking, la

Cannot escape home insulation and energy efficient ventillation if you want to ensure healthy environment from the humidity point of view. Bathroom, cooking, laundry, and people as well, all will produce humid air that will form mold on cold surfaces of an uninsulated home if not properly ventillated. Where the proper level of ventillation needs to be quite intensive for the desired effect - causing elevated energy loss or requiring supplemental heat preservation techniques - except if low level of heating (temperature) is maintained, which raises other kind of concerns.

wahern 4y ago
Older homes were designed to breath.[1] I live in San Francisco and unfortunately contractors often forget this (or don't care or never think to consider it). For example, painters will often use a non-porous latex on the outside with a common consequence that you'll quickly begin to see mold grow on the internal walls where in bygone years this wouldn't have been a problem. Or the paint may be much more prone to blistering as humidity tries to escape. Most old homes in SF originally had (or at least were modified 100+ years ago to have) gravity fed heaters--no forced air, and no return registers in each room; just a single giant return register at a low point on a bottom floor. I've spoken with A/C contractors who say that there shouldn't be any serious problems rigging up a forced air system to the output registers, even without proper return registers. And plenty of homes do this. But I guess maybe the real problems come if you then being insulating the home--can the forced-air heating system circulate air quick enough without return registers to compensate for the fact the building no longer naturally ventilates? I imagine in most cases it works well enough, but you're still moderately more likely to see mold problems. [1] To varying extents. My house was built in 1926, and it seems they used a relatively thin tar paper to wrap the house, or at least part of the house. (Unless that was somehow added much later, but I doubt it as the wall facing an adjacent house a few inches away is papered, and the siding is original on that wall.)
- citrin_ru 4y ago
  Heat recovery ventilation is more energy efficient than an old breathable house. But unfortunately it is not common even in new buildings. If you own a home you probably can install one but renters are out of luck.
  - londons_explore 4y ago
    Heat recovery ventilation is still a technology in its infancy. Typically only around 90% of the energy is recovered, even in ideal conditions. That sounds good, but considering that for 'good air', you really want to be replacing the air fully every 10 minutes. That means after ~1.5 hours, you've lost nearly all the heat in your home. Combine that with the fact the 90% is an ideal figure - in more typical installations it might be more like 50% because the incoming and outgoing airflows are not balanced, the heat exchanger is full of fluff and dust, and the humidity of the air is such that lots of energy is lost to the latent heat of vaporization. Is it worth having one if you want a well ventilated house? Yes. Will it be worth replacing it in 5-10 years when more efficient models get designed...? Probably also yes.
    - throw0101c 4y ago
      > Typically only around 90% of the energy is recovered, even in ideal conditions. As opposed to the 0% of energy recovered when a house "breathes" (i.e., leaks like a sieve) and lets out all the conditioned air? > That sounds good, but considering that for 'good air', you really want to be replacing the air fully every 10 minutes. [citation needed] ASHRAE 62.2 does not mandate nearly that much air exchange. A 2,000 sq. ft. (200 sq. m) home is about 20,000 cu. ft. of volume, and needs about 100 cfm of ventilation. And some folks (e.g., Lstiburek) think ASHRAE (at least the newer revisions) is too high: * https://www.energyvanguard.com/blog/lstiburek-has-new-ventilation-standard-resistance-may-not-be-futile/ https://www.energyvanguard.com/blog/lstiburek-has-new-ventil... * https://www.greenbuildingadvisor.com/article/how-much-fresh-air-does-your-home-need https://www.greenbuildingadvisor.com/article/how-much-fresh-...
      - Dork1234 4y ago
        Most homes are getting 4 to 7 air changes per hour just from leakage, 100cfm is nothing compared to that. It should be tied to the ACH value of the construction, as well as tied to occupancy sensors in each room.
    - kyberias 4y ago
- mihaaly 4y ago
  Correct, that is a common botched (ignorant, clueless) doing ignoring humidity aspects of highly insulated homes that was not an issue while air tightness (and consequently the energy efficiency) was on a lower level and traditional materials were being used. No excuse for those ignoring this as this is taught for many many decades now for the professionals.
- Gravityloss 4y ago
  There are lots of dimensions - old building techniques, breathing materials, natural ventilation, proper maintenance etc. And there are lots of solutions and it can be done, but it requires expertise. It's possible to mess up a very good old house made up of breathing materials with adding some plastic for example.
  - klondike_klive 4y ago
    My parents had their rafters spray-foam insulated about a decade ago, now there's a growing awareness/hysteria about condensation getting trapped in pockets and rotting the timbers. More than likely my parents were fast-talked into it.
    - bluGill 4y ago
      The important part is there is exactly one barrier that water cannot get through. Spray foam is generally good. there are different spray foams as well. Open cell and closed cell work completely different.
      - sidewndr46 4y ago
        Not if that barrier traps water against regular wooden framing members
        bluGill 4y ago
        Water will move through the wood framing to the other side and out. It takes a little longer, but we have plenty of time. It is when the water cannot get out either side that you have a problem.
        klondike_klive 4y ago
        I am hopeful that the +100r old timbers haven't suffered, unfortunately it's becoming an issue for mortgage companies, who seem to be refusing to lend as a blanket policy. We have a roof guy coming tomorrow to check out the situation though so fingers crossed. We're prepared to have it removed if necessary but aren't relishing the extra cost or the upheaval of clearing the loft.
- throw0101c 4y ago
  > Older homes were designed to breath.[1] Was it purposefully desgined to do this, or did it just happen because of construction methods of the time?
  - devonkim 4y ago
    Somewhat both. Balloon framing existed for houses when homes were heated with fireplaces and sealing the house could have been potentially dangerous as a result.
    - gfaregan 4y ago
      Why would sealing a balloon framed house be dangerous? I know that you need blocking to help stop a fire from spreading between floors.
      - ElevenLathe 4y ago
        If you heat with open fireplaces, then you can't seal the house unless you have really really good artificial ventilation (which you don't because it's 1840 still when you're building this house), regardless of how the house is built. A sealed house with a fire burning in it is a suicide machine.
        throw0101c 4y ago
        > A sealed house with a fire burning in it is a suicide machine. Modern designs use direct vent systems, where instead of using inside air for combustion, they bring in outside air (and then exhaust externally as usual): * https://www.efireplacestore.com/five-things-about-direct-vent-fireplaces.html https://www.efireplacestore.com/five-things-about-direct-ven... The warming of the house occurs via radiant heat and through any conduction of heat via the actual material of fireplace or stove.
        jefftk 4y ago
        That's not an open fireplace, though? (And so while the house is sealed, the fire is not burning with the sealed boundary of the house.)
- voisin 4y ago
  Buildings don’t need to breathe, people do. Buildings need to dry out, and there are many ways to do this that don’t involve uncontrolled air flow that destroys energy efficiency.
  - Dork1234 4y ago
    I think both of you are correct, you can have a tight building, but you need to have a way to get the moisture away from both sides of the vapor barrier. There are definitely been cases in the past 30 years were buildings were built tight without correctly considering removing moisture. https://buildingscience.com/documents/insights/bsi-001-the-perfect-wall https://buildingscience.com/documents/insights/bsi-001-the-p...
  - nemo44x 4y ago
    You're sort of wrong here and the proof is the massive graveyard of homes built in the 60's, 70's, 80's and early 90's before we really understood new techniques and materials that were being used to build homes. So many of those homes rotted out and rotted out quickly. It's similar to all the moldy basements that were finished without considering that water vapor that can't escape is the real killer. Open up a 100 year old house that has been maintained and you'll see pristine lumber that has hundreds more years if allowed to not rot. You could take an old house and bring it up to a modern standard but you would never recoup those energy savings both in terms of the cost to upgrade and the energy used to create and transport those materials. Even just replacing the single glazed, wood windows that have an uninsulated weight box with modern windows is probably not worth it if the existing windows are weatherstripped (the most important thing) and have storm windows.
- deleted 4y ago
  [deleted]
bb123 4y ago
Mechanical ventilation with Heat Recovery (MHVR) mostly solves this. Air is actively exchanged with outside to regulate humidity from cooking etc but heat from the waste air is captured and used to warm the incoming air. These are now standard in homes in the UK. https://www.cse.org.uk/advice/advice-and-support/mechanical-ventilation-with-heat-recovery https://www.cse.org.uk/advice/advice-and-support/mechanical-...
- mihaaly 4y ago
  Correct, thanks for highlighting that, I edited to explicitly note (beyond 'energy efficient ventillation') that there are heat preservation techniques to use (heat exchangers) with the elevated level of ventilation needs while avoiding high energy loss.
- _benedict 4y ago
  “Standard” is a bit strong, maybe? I think the majority of new homes still use trickle ventilation because it’s much cheaper, and not many homes have them retrofitted? They are certainly common, but I think far from standard.
  - bluGill 4y ago
    Last I checked 20 years ago it was required. This was Minnesota though, where insulation code is generally more up to date than other parts of the US.
    - _benedict 4y ago
      The original comment referenced the U.K., where it is definitely not required, but is becoming more common. I am surprised at the idea that MVHRs have been required anywhere for as much as 20 years.
      - bluGill 4y ago
        Where you are makes a big difference. 20 years ago I read about some 'passive house', and realized it was actually less insulated than the codes in Minnesota require - but it was in a mild climate so it was passive, while the more efficient houses in MN are not passive.
brnt 4y ago
For an A+++ energy rated house, you can't have holes in walls where I live. That means you can't have cooker extractors that extract, you can only have them run the air through a filter. But this is really silly, because a major 'exhaust' is water vapor, which filters don't help with. A more humid house is bad for many reasons, and often results in people opening windows anyway. Yes, an A+++ house also requires air refreshing with energy recovery, but it takes ages to get that sort of humidity out that way. Running an airco just for dehumidification is also expensive. It's short sighted imho. The extractor is precisely the right place to just move air out for all kinds of health reasons, maybe someone should work on one that recaptures some of the heat (that would also make sense!); I have not yet seen one.
- fnomnom 4y ago
  there are a lot of available ventilation solutions that recover the energy and cycle air in your use. they start at 200€ a unit and go up from there. i think the modern cooking extractors are all built into the countertops and just filter the air. at least thats the trend in germany
  - brnt 4y ago
    The point is that those systems do not integrate with extractors, and filtering only removed VOCs and particulates, not water vapour, which you would prefer to extract as well. Heat recovery from an extractor (eg remove heat from air before expelling) would achieve the goal the rating is aimed at, without compromising indoor air quality by not having a way to remove humidity. Or maybe another kind of integrated dehumidifier that discharges in your sink/plumbing maybe. Those filter-only extractors won't do for anyone serious about indoor air quality.
    - fnomnom 4y ago
      yeah but in my opinion in modern homes this is automated and regulated house-wide with the mentioned air circulators that recover the energy. they also expell humidity afaik
hedora 4y ago
I recently got a CO2 meter for our living room. The results are shockingly bad. I can't imagine having humidity issues from the sources you cite without also first having unhealthy CO2 levels. We've settled on always leaving one window slightly open if it is windy outside, or 2-3 on still days.
Jenda_ 4y ago
Or you can buy a dehumidifier (I have Sencor SDH 2020WH). This leaves you "only" with the CO2 problem, which requires less ventilation than to let out moisture (YMMV).
- dranudin 4y ago
  I have also bought a dehumidifier fo this purpose, this year. It works great. It uses less energy than I would need to keep the room dry by heating. For insulation I use thermal clothes and thus can significantly lower the room temperature with respect to the standard 20°C-21°C that people have around here.

wahern 4y ago

Older homes were designed to breath.[1] I live in San Francisco and unfortunately contractors often forget this (or don't care or never think to consider it). For example, painters will often use a non-porous latex on the outside with a common consequence that you'll quickly begin to see mold grow on the internal walls where in bygone years this wouldn't have been a problem. Or the paint may be much more prone to blistering as humidity tries to escape. Most old homes in SF originally had (or at least were modified 100+ years ago to have) gravity fed heaters--no forced air, and no return registers in each room; just a single giant return register at a low point on a bottom floor. I've spoken with A/C contractors who say that there shouldn't be any serious problems rigging up a forced air system to the output registers, even without proper return registers. And plenty of homes do this. But I guess maybe the real problems come if you then being insulating the home--can the forced-air heating system circulate air quick enough without return registers to compensate for the fact the building no longer naturally ventilates? I imagine in most cases it works well enough, but you're still moderately more likely to see mold problems. [1] To varying extents. My house was built in 1926, and it seems they used a relatively thin tar paper to wrap the house, or at least part of the house. (Unless that was somehow added much later, but I doubt it as the wall facing an adjacent house a few inches away is papered, and the siding is original on that wall.)

citrin_ru 4y ago
Heat recovery ventilation is more energy efficient than an old breathable house. But unfortunately it is not common even in new buildings. If you own a home you probably can install one but renters are out of luck.
- londons_explore 4y ago
  Heat recovery ventilation is still a technology in its infancy. Typically only around 90% of the energy is recovered, even in ideal conditions. That sounds good, but considering that for 'good air', you really want to be replacing the air fully every 10 minutes. That means after ~1.5 hours, you've lost nearly all the heat in your home. Combine that with the fact the 90% is an ideal figure - in more typical installations it might be more like 50% because the incoming and outgoing airflows are not balanced, the heat exchanger is full of fluff and dust, and the humidity of the air is such that lots of energy is lost to the latent heat of vaporization. Is it worth having one if you want a well ventilated house? Yes. Will it be worth replacing it in 5-10 years when more efficient models get designed...? Probably also yes.
  - throw0101c 4y ago
    > Typically only around 90% of the energy is recovered, even in ideal conditions. As opposed to the 0% of energy recovered when a house "breathes" (i.e., leaks like a sieve) and lets out all the conditioned air? > That sounds good, but considering that for 'good air', you really want to be replacing the air fully every 10 minutes. [citation needed] ASHRAE 62.2 does not mandate nearly that much air exchange. A 2,000 sq. ft. (200 sq. m) home is about 20,000 cu. ft. of volume, and needs about 100 cfm of ventilation. And some folks (e.g., Lstiburek) think ASHRAE (at least the newer revisions) is too high: * https://www.energyvanguard.com/blog/lstiburek-has-new-ventilation-standard-resistance-may-not-be-futile/ https://www.energyvanguard.com/blog/lstiburek-has-new-ventil... * https://www.greenbuildingadvisor.com/article/how-much-fresh-air-does-your-home-need https://www.greenbuildingadvisor.com/article/how-much-fresh-...
    - Dork1234 4y ago
      Most homes are getting 4 to 7 air changes per hour just from leakage, 100cfm is nothing compared to that. It should be tied to the ACH value of the construction, as well as tied to occupancy sensors in each room.
  - kyberias 4y ago
mihaaly 4y ago
Correct, that is a common botched (ignorant, clueless) doing ignoring humidity aspects of highly insulated homes that was not an issue while air tightness (and consequently the energy efficiency) was on a lower level and traditional materials were being used. No excuse for those ignoring this as this is taught for many many decades now for the professionals.
Gravityloss 4y ago
There are lots of dimensions - old building techniques, breathing materials, natural ventilation, proper maintenance etc. And there are lots of solutions and it can be done, but it requires expertise. It's possible to mess up a very good old house made up of breathing materials with adding some plastic for example.
- klondike_klive 4y ago
  My parents had their rafters spray-foam insulated about a decade ago, now there's a growing awareness/hysteria about condensation getting trapped in pockets and rotting the timbers. More than likely my parents were fast-talked into it.
  - bluGill 4y ago
    The important part is there is exactly one barrier that water cannot get through. Spray foam is generally good. there are different spray foams as well. Open cell and closed cell work completely different.
    - sidewndr46 4y ago
      Not if that barrier traps water against regular wooden framing members
      - bluGill 4y ago
        Water will move through the wood framing to the other side and out. It takes a little longer, but we have plenty of time. It is when the water cannot get out either side that you have a problem.
        klondike_klive 4y ago
        I am hopeful that the +100r old timbers haven't suffered, unfortunately it's becoming an issue for mortgage companies, who seem to be refusing to lend as a blanket policy. We have a roof guy coming tomorrow to check out the situation though so fingers crossed. We're prepared to have it removed if necessary but aren't relishing the extra cost or the upheaval of clearing the loft.
throw0101c 4y ago
> Older homes were designed to breath.[1] Was it purposefully desgined to do this, or did it just happen because of construction methods of the time?
- devonkim 4y ago
  Somewhat both. Balloon framing existed for houses when homes were heated with fireplaces and sealing the house could have been potentially dangerous as a result.
  - gfaregan 4y ago
    Why would sealing a balloon framed house be dangerous? I know that you need blocking to help stop a fire from spreading between floors.
    - ElevenLathe 4y ago
      If you heat with open fireplaces, then you can't seal the house unless you have really really good artificial ventilation (which you don't because it's 1840 still when you're building this house), regardless of how the house is built. A sealed house with a fire burning in it is a suicide machine.
      - throw0101c 4y ago
        > A sealed house with a fire burning in it is a suicide machine. Modern designs use direct vent systems, where instead of using inside air for combustion, they bring in outside air (and then exhaust externally as usual): * https://www.efireplacestore.com/five-things-about-direct-vent-fireplaces.html https://www.efireplacestore.com/five-things-about-direct-ven... The warming of the house occurs via radiant heat and through any conduction of heat via the actual material of fireplace or stove.
        jefftk 4y ago
        That's not an open fireplace, though? (And so while the house is sealed, the fire is not burning with the sealed boundary of the house.)
voisin 4y ago
Buildings don’t need to breathe, people do. Buildings need to dry out, and there are many ways to do this that don’t involve uncontrolled air flow that destroys energy efficiency.
- Dork1234 4y ago
  I think both of you are correct, you can have a tight building, but you need to have a way to get the moisture away from both sides of the vapor barrier. There are definitely been cases in the past 30 years were buildings were built tight without correctly considering removing moisture. https://buildingscience.com/documents/insights/bsi-001-the-perfect-wall https://buildingscience.com/documents/insights/bsi-001-the-p...
- nemo44x 4y ago
  You're sort of wrong here and the proof is the massive graveyard of homes built in the 60's, 70's, 80's and early 90's before we really understood new techniques and materials that were being used to build homes. So many of those homes rotted out and rotted out quickly. It's similar to all the moldy basements that were finished without considering that water vapor that can't escape is the real killer. Open up a 100 year old house that has been maintained and you'll see pristine lumber that has hundreds more years if allowed to not rot. You could take an old house and bring it up to a modern standard but you would never recoup those energy savings both in terms of the cost to upgrade and the energy used to create and transport those materials. Even just replacing the single glazed, wood windows that have an uninsulated weight box with modern windows is probably not worth it if the existing windows are weatherstripped (the most important thing) and have storm windows.
deleted 4y ago
[deleted]

bb123 4y ago

Mechanical ventilation with Heat Recovery (MHVR) mostly solves this. Air is actively exchanged with outside to regulate humidity from cooking etc but heat from the waste air is captured and used to warm the incoming air. These are now standard in homes in the UK. https://www.cse.org.uk/advice/advice-and-support/mechanical-ventilation-with-heat-recovery https://www.cse.org.uk/advice/advice-and-support/mechanical-...

mihaaly 4y ago
Correct, thanks for highlighting that, I edited to explicitly note (beyond 'energy efficient ventillation') that there are heat preservation techniques to use (heat exchangers) with the elevated level of ventilation needs while avoiding high energy loss.
_benedict 4y ago
“Standard” is a bit strong, maybe? I think the majority of new homes still use trickle ventilation because it’s much cheaper, and not many homes have them retrofitted? They are certainly common, but I think far from standard.
- bluGill 4y ago
  Last I checked 20 years ago it was required. This was Minnesota though, where insulation code is generally more up to date than other parts of the US.
  - _benedict 4y ago
    The original comment referenced the U.K., where it is definitely not required, but is becoming more common. I am surprised at the idea that MVHRs have been required anywhere for as much as 20 years.
    - bluGill 4y ago
      Where you are makes a big difference. 20 years ago I read about some 'passive house', and realized it was actually less insulated than the codes in Minnesota require - but it was in a mild climate so it was passive, while the more efficient houses in MN are not passive.

brnt 4y ago

For an A+++ energy rated house, you can't have holes in walls where I live. That means you can't have cooker extractors that extract, you can only have them run the air through a filter. But this is really silly, because a major 'exhaust' is water vapor, which filters don't help with. A more humid house is bad for many reasons, and often results in people opening windows anyway. Yes, an A+++ house also requires air refreshing with energy recovery, but it takes ages to get that sort of humidity out that way. Running an airco just for dehumidification is also expensive. It's short sighted imho. The extractor is precisely the right place to just move air out for all kinds of health reasons, maybe someone should work on one that recaptures some of the heat (that would also make sense!); I have not yet seen one.

fnomnom 4y ago
there are a lot of available ventilation solutions that recover the energy and cycle air in your use. they start at 200€ a unit and go up from there. i think the modern cooking extractors are all built into the countertops and just filter the air. at least thats the trend in germany
- brnt 4y ago
  The point is that those systems do not integrate with extractors, and filtering only removed VOCs and particulates, not water vapour, which you would prefer to extract as well. Heat recovery from an extractor (eg remove heat from air before expelling) would achieve the goal the rating is aimed at, without compromising indoor air quality by not having a way to remove humidity. Or maybe another kind of integrated dehumidifier that discharges in your sink/plumbing maybe. Those filter-only extractors won't do for anyone serious about indoor air quality.
  - fnomnom 4y ago
    yeah but in my opinion in modern homes this is automated and regulated house-wide with the mentioned air circulators that recover the energy. they also expell humidity afaik

hedora 4y ago

I recently got a CO2 meter for our living room. The results are shockingly bad. I can't imagine having humidity issues from the sources you cite without also first having unhealthy CO2 levels. We've settled on always leaving one window slightly open if it is windy outside, or 2-3 on still days.

Jenda_ 4y ago

Or you can buy a dehumidifier (I have Sencor SDH 2020WH). This leaves you "only" with the CO2 problem, which requires less ventilation than to let out moisture (YMMV).

dranudin 4y ago
I have also bought a dehumidifier fo this purpose, this year. It works great. It uses less energy than I would need to keep the room dry by heating. For insulation I use thermal clothes and thus can significantly lower the room temperature with respect to the standard 20°C-21°C that people have around here.