6 ms·

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). F

by 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
    The standard to replace all air is about 2 hours which is 12 times longer than the 10 minutes you stated here.
  - valenterry 4y ago
    > That sounds good, but considering that for 'good air', you really want to be replacing the air fully every 10 minutes. That obviously does not make any sense. You at least want to know the volume of the room/house before giving any number...
    - anonymous_sorry 4y ago
      It's not obvious to me why this doesn't make sense. What "Replacing the air fully" equates to in terms of volume is already a factor of the size of the room/house. You might want to know what volume of air that actually was to understand energy usage, but gp was talking about air quality, not energy efficiency.
- mharig 4y ago
  And the ventilation ducts and filters are nice hotbeds for mold and bacteria.
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]

by wahern 4y ago

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
  The standard to replace all air is about 2 hours which is 12 times longer than the 10 minutes you stated here.
- valenterry 4y ago
  > That sounds good, but considering that for 'good air', you really want to be replacing the air fully every 10 minutes. That obviously does not make any sense. You at least want to know the volume of the room/house before giving any number...
  - anonymous_sorry 4y ago
    It's not obvious to me why this doesn't make sense. What "Replacing the air fully" equates to in terms of volume is already a factor of the size of the room/house. You might want to know what volume of air that actually was to understand energy usage, but gp was talking about air quality, not energy efficiency.
mharig 4y ago
And the ventilation ducts and filters are nice hotbeds for mold and bacteria.

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]